 |
|---|
Follow this link back to the Organic Chemistry Homepage.
Copyright 2004
| Section | Learning Objectives |
|---|---|
| 1.1, 1.2 | Note the pervasive relevance of organic chemistry to life and society. |
| 1.3 | Understand molecular and empirical formulas. Know valences for C, H, N, O, halogens, S. Learn bonding arrangements for the above elements. Understand constitutional isomers and connectivity. |
| 1.4 | Know the octet rule and ramifications thereof. Understand ionic and covalent bonds and electronegativity trends. |
| 1.5 | Be able to draw proper Lewis structures for neutral and ionic species. |
| 1.6 | Note some exceptions to the octet rule. |
| 1.7 | Be able to calculate formal charge on any atom and determine overall ionic charge. |
| 1.8 | Understand essential principles of resonance and be able to draw resonance structures for simple structures where resonance is possible. |
| 1.9 | Understand wave characteristics (phase interactions) leading to reinforcement , and interference. Accept the general relevance of wave properties to atomic structure. |
| 1.10 | Understand interpretation of the square of the wave function (psi2) as indicating a region of space where probability of finding an electron is high. Learn the three dimensional shapes and orientations of s and p orbitals derived from wave functions. Be able to draw proper valence electron configurations for C, N, O, and halogens. |
| 1.11 | Understand the derivation of a specific number of molecular orbitals from combinations of a given number of atomic orbitals. |
| 1.12 | Be able to apply electron configurations and the principle of orbital hybridization to predict the structure of sp3, sp2, and sp hybridized atoms. Understand the 3-D arrangement of atoms in an alkane. Understand the origin of sp3 hybridization through electron promotion and hybridization. Know unequivocally the structure of an sp3 hybridized carbon atom and the orbital representation of the its sigma bonds. Understand that rotation can occur about a single bond. |
| 1.13 | Understand the 3-D arrangement of atoms that are part of an alkene double bond. Understand the origin of sp2 hybridization through electron promotion and hybridization. Know unequivocally the orbital structure of an sp2 hybridized atom and the orbital representation of a pi bond with a sigma bond framework. Understand the ramifications of restricted rotation about pi bonds and the potential for cis-trans isomerism, as compared to free rotation about sigma bonds. |
| 1.14 | Understand the 3-D arrangement of atoms that are part of an alkyne triple bond. Understand the origin of sp orbitals through hybridization and know the orbital structure of an sp hybridized atom. Understand the overlap of adjacent p orbitals from sp hybridized carbon atoms leading to the orthogonal relationship of the two pi bonds in an alkyne. |
| 1.15 | Use this section to unify your understanding of quantum mechanics concepts discussed earlier. |
| 1.16 | Be able to use the VSEPR model to predict tetrahedral, trigonal planar, and linear molecular geometries for various examples. |
| 1.17 | Gain unquestionable proficiency in representing organic molecules in their dash, condensed, bond-line, and three-dimensional (dash-wedge) structural formulas. |
| Summary and Review Tools |
Use the Key Terms and Concepts list as a self-test for your understanding of the listed terms. Use the Concept Map to highlight the relationships between concepts and for an overall summary and review. |
| Section | Learning Objectives |
|---|---|
| 2.1 | Note that organic compounds are organized into families according to their functional group, and that infrared spectroscopy is one way to detect functional groups. |
| 2.2 | Understand the structural meaning of the terms hydrocarbon, alkanes, alkenes, alkynes, aromatic, saturated, and unsaturated. Gain a 3-D sense of the structure of alkanes based on their hybridization and bonding. |
| 2.3, 2.4 | Be able to apply the principles of electronegativity and bond polarization, along with molecular geometry, to predict the overall polarity or lack thereof in any given molecule. Be able to interpret a map of electrostatic potential as an illustration of charge distribution in a molecule. |
| 2.5 | Understand what alkyl groups are. Know the names and be able to draw formulas for all alkyl ("R") groups of three carbons or fewer. Understand the notion of a functional group. Know the structural meaning of the names and shorthand representations for the phenyl and benzyl groups. |
| 2.6 | Be able to write the general formulas of 1o (primary), 2o (secondary), and 3o (tertiary) alkyl halides (using R groups) and identify real examples of each type. |
| 2.7 | Be able to write the general formulas of 1o (primary), 2o (secondary), and 3o (tertiary) alcohols (using R groups) and identify examples of each type in a real molecule. |
| 2.8 | Be able to write the general formula of an ether and identify the ether functional group in real examples. |
| 2.9 | Be able to write the general formulas of 1o (primary), 2o (secondary), and 3o (tertiary) amines (using R groups) and identify examples of each type in a real molecule. |
| 2.10 | Know the 3-D structure and hybridization of the carbonyl group. Be able to write the general formulas of aldehydes and ketones and identify both functional groups in real examples. |
| 2.11 | Be able to write the general formulas of carboxylic acids, amides, and esters and identify these functional groups in real examples. |
| 2.12 | Be able to write the general formula for a nitrile and to identify this functional group in real examples. |
| 2.13 | Know the dash and all condensed structural formula representations for the above functional groups and be able to draw every one from memory. Not the summary in Table 2.3. |
| 2.14, 2.14 A-F | Know the various types of intermolecular forces that are possible and understand their influence on physical properties (such as mp, bp and solubility) for a given molecule. |
| 2.15 | Note the summary of attractive electric forces in Table 2.6. |
| 2.16 | Understand that atoms and groups of atoms vibrate about the covalent bonds that connect them. Molecular vibrations can be thought of as balls (the atoms) connected by springs (the bonds) oscillating at frequencies in the infrared region specific to the types of bonds and atoms involved. Begin to use IR spectra for functional group identification (assuming a frequency chart is provided, e.g. Table 2.7). |
| 2.16A | Recognize 3000 cm-1 as the "dividing line between sp2 (3200-3000 cm-1) and sp3 (3000-2800 cm-1) carbon-hydrogen stretches. Be able to use an IR spectrum to infer the presence or absence in a molecule of these respective types of C-H bonds. |
| 2.16B | Be able to use IR spectra to infer the presence or absence of various functional groups (with the aid of a frequency correlation chart like that found inside the back cover or Table 2.7). Understand this use as probably the most important application of IR spectroscopy in structure elucidation. |
| Summary and Review Tools |
Use the Key Terms and Concepts list as a self-test for your understanding of the listed terms. Use the Concept Map to highlight the relationships between concepts and for an overall summary and review. |
| Section | Learning Objectives |
|---|---|
| 3.1 | Note the general changes in structure accompanying substitution, addition, elimination, and rearrangement reactions. From the "A Mechanism for the Reaction" section, understand the concept of a mechanism as a stepwise description of events in a chemical reaction |
| 3.1A | Understand that cleavage of a bond to a carbon atom could conceivably occur in three ways: homolytically (to form a radical), or heterolytically with the carbon either keeping or losing both electrons of the bond (to form a carbanion or carbocation, resp.) Understand the general meaning of heterolytic and homolytic bond cleavage. |
| 3.2A | Review concepts of Bronsted-Lowry Acids and Bases. |
| 3.2B | Understand Lewis acids and bases as generally applicable to acid-base theory. Be able to classify compounds as Lewis acids or bases, especially with regard to examples involving organic compounds. |
| 3.2C | Note the importance of the attraction of opposite charges. Be able to interpret a map of electrostatic potential as an illustration of charge distribution. |
| 3.3 | Know the general structure of a carbocation and carbanion, Learn the basic definition/character of nucleophiles and electrophiles. |
| 3.4 | Understand the precise use of the double-barbed curved arrow and be able to draw them appropriately and with accurate meaning. |
| 3.5 | Understand the mathematical derivation of Ka and pKa. Know the significance of both Ka and pKa regarding acid (and conjugate base) strength. Be able to write the conjugate base or conjugate acid from any acid or base, respectively, and the corresponding acid or base from the respective conjugate . |
| 3.6 | Be able to use Ka or pKa values to predict the direction of an acid-base reaction. |
| 3.7 | Understand the influences of bond strength (to the acidic hydrogen), electronegativity, hybridization, and inductive effects on acidity. |
| 3.8 | Know the meaning of endothermic, exothermic and enthalpy as applied to energy changes in chemical reactions. |
| 3.9 | Understand the relationship of a positive or negative value of deltaGo to the equilibrium position of a reaction. |
| 3.10 | Know the relative acidities of carboxylic acids and alcohols. |
| 3.11 | Recognize the ability of protic solvents to solvate the anions formed upon ionization of an acid. |
| 3.12 | Understand the capacity of organic compounds containing oxygen to act as bases and engage in proton transfer reactions. |
| 3.13 | Note the format and stepwise detail in this first example of a reaction mechanism. |
| 3.14 | Understand the need for solvents other than water when bases stronger than hydroxide ion are used (understand the leveling effect of water in these cases). Begin to recognize some exceptionally strong bases (e.g. NaNH2, NaH, and alkyllithium reagents (RLi). |
| 3.15 | Understand the ability to introduce deuterium and tritium by acid-base reactions. |
| Summary and Review Tools |
Use the Key Terms and Concepts list as a self-test for your understanding of the listed terms. Use the Concept Map to highlight the relationships between concepts and for an overall summary and review. |
| Section | Learning Objectives |
|---|---|
| 4.1 | Recognize petroleum as the primary natural source of alkanes and aromatic hydrocarbons. Know the general formulas for an alkane and cycloalkane. |
| 4.2 | Know the general three-dimensional structure of alkanes, based on the appropriate hybridization state of carbon, regardless of the type of formula presented. Understand the structural meanings as pertains to alkanes of the designations "straight-chain" (or unbranched) and branched. Recall that constitutional isomers have different physical properties. |
| 4.3, 4.3A-F | Learn the IUPAC names of alkanes through C20. Learn all the alkyl group names from C1 through C4. Be able to apply the IUPAC rules for naming branched chain alkanes. Learn the names of branched alkyl groups through C5. including the meaning of prefixes iso-, sec-, tert-. Be able to classify hydrogens as 1o, 2o, or 3o. Be able to name alkyl halides and alcohols using the IUPAC system. |
| 4.4 | Be able to name monocyclic alkanes (section 4.4A). Read section 4.4B for interest. |
| 4.5 | Be able to correctly apply the IUPAC nomenclature rules to the naming of any alkene or cycloalkene. Be able to recognize vinyl and allyl groups by their respective substructures. |
| 4.6 | Be able to correctly name any alkyne using the IUPAC system. |
| 4.7 | Recognize the trends in mp and bp among hydrocarbon homologs. Know the general density and solubility properties of alkanes and cycloalkanes, as compared to water. |
| 4.8 | Be able to perform conformational analyses on simple alkanes using Newman projections to draw the various conformations. Recognize a given conformation as being staggered or eclipsed. |
| 4.9 | Understand the significance of torsional strain regarding conformational anyalysis. Recognize a given conformation as being anti or gauche, as well as staggered or eclipsed. |
| 4.10 | Know the relative order of stability for cycloalkanes from cyclohexane to cyclopropane. Consider the relative heats of combustion (section 4.10A,B) only if interested in this data and further analysis. |
| 4.11 | Understand the influence of angle and torsional strain on the overall ring strain in cyclopropane and cyclobutane, as compared to cyclopentane and cyclohexane. |
| 4.12 | Be able to recognize and draw clearly the boat and chair conformations of cyclohexane, especially the chair conformation, showing correct 3-D perspective. Be able to draw a Newman projection for cyclohexane, viewed along any pair of C-C bonds. |
| 4.13 | Learn to identify the axial and equatorial positions on the chair conformation of cyclohexane. Be able to draw cyclohexane so that axial and equatorial positions of substituents are absolutely unambiguous. Understand the origin of 1,3-diaxial interactions and the basis for the relatively greater stability of chair conformations with substituents in equatorial orientations. Learn to depict a chair-chair conformational ring flip with accurate drawings showing the changes in axial and equatorial orientations of groups. |
| 4.14 | Understand the possibility for cis and trans stereoisomers in disubstituted cycloalkanes. Be able to draw both the unrealistic "flat" ring structures and realistic chair conformational structures for disubstituted cyclohexanes. Correctly place cis or trans groups in axial or equatorial orientations, depending on the preferred, lowest energy conformation for the chair. |
| 4.15 | Consider the structures of some representative bicyclic and polycyclic alkanes. Note the biological role of some relatively simple hydrocarbons.& |
| 4.16 | Recognize the relatively inert character of alkanes, aside from combustion. |
| 4.17 | Learn the reagents, reaction conditions, types of starting materials
required and products formed for the reactions presented for synthesis of
alkanes in sections 4.17A-C: i) hydrogenation of alkenes and alkynes, ii) reduction of alkyl halides, and iii) alkylation of terminal alkynes. Be able to write examples of each reaction using R groups for generalized reactants and products. Be able to translate an understanding of the general reactions to using reaction conditions with specific molecules to form the corresponding products. |
| 4.18 | Understand how Lewis acid-base chemistry and the attraction of oppositely charged species are central to organic reactions and synthesis. . |
| 4.19 | Note the relevance to health care and quality of life of carrying out organic syntheses of useful molecules. Begin to understand the rational use of retrosynthetic analysis. Be able to envision specific and logical retrosynthetic disconnections, and the intermediates that would be involved, when planning syntheses of molecules like those used in problems in this chapter. Be able to evaluate the relative merit of various synthetic routes to a given molecule. |
| Summary and Review Tools |
Use the Key Terms and Concepts list as a self-test for your understanding of the listed terms. Use the Concept Map to highlight the relationships between concepts and for an overall summary and review. |
| Section | Goals |
|---|---|
| 5.1 | Know and understand the definitions of chiral and superposable. Note examples of chirality in nature and the importance of chirality to life. |
| 5.2 | Know the definitions of constitutional isomers, stereoisomers, enantiomers, and diastereomers, and their relationship to each other. Be able to classify the specific type of isomeric relationship between any one compound and another. |
| 5.3 | Be able to identify tetrahedral and trigonal stereogenic centers in molecules. Be able to identify a compound as being chiral or achiral by testing for superposability on its mirror image. Work on visualizing molecules in three-dimensions, especially regions involving stereogenic centers. Do this by making models and drawing dash-wedge structures of models, and by making models of drawn structures. Understand the importance of mirror planes for determining whether an enantiomer to a given molecule can exist. Understand the effect of interchanging the position of any two groups at a tetrahedral stereogenic center. |
| 5.4 | Note the profound importance of chirality in natural products and biologically active molecules, and its relevance to health care. |
| 5.5 | Consider the historical origin of our understanding of stereochemistry. |
| 5.6 | Be able to use the mirror plane test for chirality. |
| 5.7 | In general, be able to assign the R or S configuration to any tetrahedral stereogenic center by correctly determing the relative priorities of groups bonded to the stereogenic center and determining the direction of priority rotation. Specifically, be able to apply the priority rules to any type of attached group, including those with multiple bonds. Develop expert facility at visualizing the direction of rotation of the attached groups at a tetrahedral stereogenic center, according to their priorities and with a mind's eye view from inside the "inverted umbrella" of the tetrahedron. |
| 5.8 | Understand the definition of optical activity as the rotation of plane polarized light by chiral molecules. Know that optical activity is measured using instruments called polarimeters. Recognize that no obvious correlation exists between the sign of rotation (+ or -) for an optically active molecule and the R or S configuration of enantiomers. Understand that an optical rotation measurement can be standardized for use as a physical constant for a given optically active substance by calculating what is known as the specific rotation, by taking into account sample characteristics such as concentration, etc. |
| 5.9 | Consider the theoretical origin of optical activity as explained by counterrotating circularly polarized light beams that travel with different velocities through a chiral medium. Understand the meaning of the term racemic mixture (or racemic form, or racemate). Have an intuitive understanding of why there is no optical activity in a racemic mixture. |
| 5.10 | Understand that a racemic mixture results when a chiral molecule is formed by a chemical reaction between achiral starting materials and achiral reagents. Consider how an optically active product might result from using either chiral starting materials or chiral reagents. |
| 5.11 | Note the importance of chirality in drug design and manufacture. |
| 5.12 | Understand the ramifications of having more than one stereogenic center in a molecule ("n" stereogenic centers) with regard to the total number of isomers possible (2n), how many enantiomer pairs are possible (2n- 1) and how many diastereomers could exist (2n-1). Understand the relationship between diastereomers with regard to physical constants. Be able to identify meso compounds. Be able to use the R-S system to name compounds with more than one stereogenic center. |
| 5.13 | Understand how to draw and interpret Fischer projection formulas, while recognizing the advantages and pitfalls of their use. |
| 5.14 | Understand how stereoisomerism applies to cyclic molecules and be able to recognize cases where planes of symmetry may influence the existence or number of stereoisomers in cyclic compounds. |
| 5.15 | Understand how the R or S configuration of a stereogenic center may or not be affected by the breaking and forming of bonds to the stereogenic center (according to the priorities of the new and old groups), and also how the R or S configuration of a stereogenic center may or not be affected by the breaking of bonds not directly attached to the stereogenic center (according to how a group's priority might change through remote alteration). Understand the process of relating configurations between molecules by use of reactions with known stereochemical outcome. |
| 5.16 | Understand the principle behind methods for the separation of enantiomers, i.e., that reversible conversion of a pair of enantiomers into diastereomeric species results in materials of differing physical properties, which after separation could be used to regenerate each original enantiomer in isolated form. |
| 5.17,18 | Consider the potential for chirality involving atoms other than carbon, molecules whose conformers have high rotational barriers (atropisomers), and allenes. |
| Summary and Review Tools |
Use the Key Terms and Concepts list as a self-test for your understanding of the listed terms. Use the Concept Map to highlight the relationships between concepts and for an overall summary and review. |
| Section | Goals |
|---|---|
| 6.1 | Know the general structural characteristics of an alkyl halide, re: bond polarity, geometry, etc. Be able to readily identify an alkyl halide as 1o (primary), 2o (secondary), or 3o (tertiary). Be able to recognize vinylic and aryl halides (significant because vinylic and aryl halides do not react by the mechanisms in Chapter 6). Note the names for some common organic halides, the solubility characteristics of alkyl halides, and trends in boiling point and density according to type of alkyl group or type of halogen (for a given alkyl group). |
| 6.2 | Be able to write the general reaction for a nucleophilic substitution reaction and identify the nucleophile, substrate (e.g., alkyl halide), and leaving group. |
| 6.3 | Gain thorough understanding of what a nucleophile is and be able to recognize the nucleophilic participant in a reaction. Be able to recall specific examples of nucleophiles. Understand the general character of nucleophiles, such that you could identify potentially nucleophilic species in a reaction. For specific examples where the nucleophilic atom bears a hydrogen (e.g. HOH, ROH), understand the reason for a proton transfer step after the substitution). |
| 6.4 | Understand the general nature of a leaving group as a species that departs with a pair of electrons (as during a nucleophilic substitution reaction). Learn to recognize the leaving group in substrates for nucleophilic substitution. Recognize that the better a leaving group can accommodate (stabilize) the electron pair it takes with it, the better will be the leaving group. |
| 6.5 | Know the meaning of SN2 in terms of reaction order and the effect of the concentration of reactants on rate. Understand that in SN2 reactions both the nucleophile and alkyl halide substrate are involved in the rate determining step. |
| 6.6 | As one of the most important sections in your study of organic chemistry, commit to memory the general aspects of the SN2 reaction depicted in this section. Pay special attention to the site of nucleophic attack (back side with respect to the leaving group), the structure of the transition state (involving concerted bond forming to the nucleophile and bond breaking to the leaving group), and the configuration of the product as compared to the substrate (inversion of the tetrahedral center). |
| 6.7 | Be able to draw a generic free energy diagram for an SN2 reaction, labeling the transition state, and showing the overall free energy change for the reaction (deltaGo), whether it be endergonic or exergonic. Understand the influence of the magnitude of the energy of activation (deltaGo) on the rate of reaction. Understand the influence of temperature on reaction rate. |
| 6.8 | Further cement in place an understanding of SN2 reaction as occuring by back side attack of the nucleophile with inversion of configuration and simultaneous bond forming and breaking. Understand the ramifications of inversion in SN2 reactions that take place at a stereogenic center. Be able to draw from memory and in three-dimensions a generic mechanism for an SN2 reaction, including the transition state. |
| 6.9 | Know that SN1 reactions are unimolecular in the rate determining step. |
| 6.10 | Ingrain the sequence of steps involved in any general SN1 reaction (see p. 245 for a specific example): 1) departure of the leaving group (with the pair of electrons that bonded the LG to the substrate), 2) concomitant formation of a carbocation at the carbon that lost the LG, and 3) attack of the nucleophile on the carbocation. Understand that there may be proton transfer steps necessary, depending on the nature of the nucleophile and leaving group, but consider the above three stages the essential components of every SN1 reaction. |
| 6.11 | Cement an understanding of the orbital and 3D structure of a carbocation, especially the planar nature of the sp2 carbon and the vacant p orbital. Know the general trend in relative carbocation stability. |
| 6.12A | Understand how the stereochemical outcome of an SN1 reaction at a stereogenic center (i.e. racemization) follows from the planar structure of the intermediate carbocation (allowing both frontside and backside attack by the nucleophile). Be able to draw from memory and in three-dimensions where appropriate the stepwise mechanism for a generic SN1 reaction, as outlined in the three steps of section 6.11. |
| 6.12B | Recognize solvents as potential nucleophiles in SN1 reactions and understand the concomitant proton transfer steps that are required. |
| 6.13 | Be able to list and discuss the four most important factors effecting rates of SN1 and SN2 reactions. |
| 6.13A | Know how structure affects the rate of SN1 and SN2 reactions, i.e. steric hindrance for SN2 and relative carbocation stability for SN1. |
| 6.13B | Be able to assess the relative strength of a nucleophile, based on it's charge or lack thereof, and relative basicity. Understand the effect of concentration on the rate of SN2 reactions. |
| 6.13C | Understand why polar aprotic solvents facilitate SN2 reactions. Understand the structural difference between polar and aprotic solvents and be able togive examples of each. |
| 6.13D | Understand the ionizing ability of polar protic solvents and their tendency to increase the rate of SN1 reactions. Recognize that while water is a good ionizing solvent, many organic compounds are not soluble in water, hence organic solvents such as methanol and alcohol are frequently mixed with water to assist in solvation of the organic reactants. |
| 6.13E | Learn some of the common leaving groups and recognize the common ability among them to stabilize/accomodate the pair of electrons taken with them when they act as leaving groups. Understand the inverse relationship of base strength to leaving group ability. |
| 6.13F | Review factors that influence which type of substitution mechanism will be favored. |
| 6.14 | Be able to prepare compounds with a variety of functional groups by transformation or incorporation of functional groups using SN2 reactions on suitable substrates. Recall the unreactivity of vinyl and aryl halides in SN1 and SN2 reactions. |
| 6.15 | Be able to draw from memory a generic example of a dehydrohalogenation reaction. Be able to recognize hydrogens (beta-hydrogens) eligible for removal by a base, and the position of the double bond that will form upon departure of the leaving group (from the alpha-carbon). |
| 6.15B | Know the common bases used for dehydrohalogenation (also called 1,2-elimination). |
| 6.16 | Ingrain in memory the general mechanism of an E2 reaction (in three-dimensions and including the transition state, as depicted in this section). |
| 6.17 | Understand the mechanism of an E1 reaction, recognizing the possibility for elimination of any beta- hydrogen from a carbocation intermediate, in addition to the possiblity for an SN1 substitution. |
| 6.18 | Understand the combined influence of factors such as base/nucleophile strength and substrate structure (steric hindrance) with regard to competition between SN2 and E2 reactions. With regard to SN1 and E1 reactions, recognize the inherent difficulty in directing a tertiary substrate exclusively toward substitution. If substitution is desired, attempt to use a 2o or 1o substrate. If elimination is desired, use a strong base. |
| 6.19 | Be able to prepare for yourself from memory a comparison of all factors influencing whether each substrate type will undergo an SN1, SN2, E1, or E2 reaction. |
| Summary and Review Tools |
Use the Mechanism Review to consider the factors that influence the spectrum of reactivity from prrimarily SN2, to mixture of SN2 and E2, to primarily E2, to a mixture SN1 and E1. Use the Key Terms and Concepts list as a self-test for your understanding of the listed terms. |
| Section | Goals |
|---|---|
| 7.1 | Note that olefin is an old term sometimes used to refer to an alkene. |
| 7.2 | Be able to apply the (E) - (Z) system for designating alkene diastereomers (as a prefered alternative to cis and trans designations). |
| 7.3 | Know the relative order of alkene stabilities (Section 7.3B) and understand the thermodynamic evidence for this order (Sections 7.3A). |
| 7.4 | Understand the relative stability of cycloalkenes as a function of ring size. |
| 7.5 | Gain acquaintance with the two general types of elimination reactions presented here for synthesis of alkenes . |
| 7.6 | Review the essential E2 mech. Understand that if synthesis of an alkene is desired, conditions favoring an E2 mechanism should be chosen. Be able to describe reaction conditions favoring an E2 mechanism. |
| 7.6A | Understand how a given elimination reaction might proceed to give more than one product. Be able to identify all hydrogens eligible for removal in an elimination reaction. Be able to predict the Zaitsev (more stable alkene) product from a given reaction. |
| 7.6B | Know conditions that could be used to favor elimination to form a less substituted alkene. |
| 7.6C | Be able to draw from memory the anti coplanar transition state for an E2 reaction. Be able to analyze and predict the products from elimination reactions involving cyclohexane substrates. |
| 7.7 | Know conditions for preparation of alkenes by dehydration of alcohols. Understand the effect on ease of dehydration with respect to alcohol structure, and the potential for carbocation rearrangements (see section 7.8). |
| 7.7A | Be able to draw from memory a stepwise mechanism for acid-catalyzed alcohol dehydration. Recognize this reaction as an E1 process for tertiary and secondary alcohols. |
| 7.7B | Recall the trend of carbocation stability and understand its influence on ease of alcohol dehydration. |
| 7.7C | Recognize that alcohol dehydration of a primary alcohol is essentially an E2 process, or that it may involve hydride or alkanide migration with concommitant formation of a more stable carbocation. |
| 7.8 | Be able to recognize the potential for and predict molecular rearrangements in a given substrate as a function of carbocation stability. Be able to draw correct detailed curly arrow mechanisms for both hydride and alkanide (alkyl) migrations, showing the initial carbocation and the carbocation resulting after rearrangement. |
| 7.9 | Be able to use debromination of a vicinal dibromide or double elimination of geminal dihalides for synthesis of an alkene. |
| 7.10 | Recognize the acidity of terminal alkynes and know conditions (use of the appropriate base) for forming an alkynide anion. |
| 7.11 | Be able to utilize alkynide anions (starting with the corresponding alkyne) for SN2 reactions to from new carbon-carbon bonds. Recognize the limitation of only being able to use 1o alkyl halide substrates (otherwise E2 occurs). |
| 7.12 | Review the conditions and characteristics of the catalytic hydrogenation of alkenes. |
| 7.13 | Understand the function of the metal catalyst in catalytic hydrogenation and the necessary stereochemistry resulting from hydrogen addition (syn) by catalytic hydrogenation. (Note, for interest, the significance of homogeneous asymmetric catalytic hydrogenation and the relevance of BINAP atropisomers to these types of chiral catalysts.) |
| 7.14 | Know reagents and reaction conditions for i) the exhaustive hydrogenation of an alkyne (to form an alkane by addition of two molar equivalents of hydrogen), ii) partial hydrogenation of an alkyne (to form an alkene by one molar equivalent of hydrogen), and iii) conditions that will lead, as desired, to specifically syn or anti addition of hydrogen to produce Z or E alkenes, respectively. |
| 7.15 | Be able to utilize the Index of Hydrogen Deficiency as a clue to structure based on the molecular formula. |
| Summary and Review Tools |
Use the Mechanism Review to summarize aspects that favor reaction by an E2 or E1 mechanism. Use the Synthetic Connections box to review reactions that allow synthetic relationships between types of compounds you have studied thus far. Use the Key Terms and Concepts list as a self-test for your understanding of the listed terms. |
| Section | Goals |
|---|---|
| 8.1 | Recall the 3-D orbital structure of alkenes and the pi bond. Understand how a pi bond can be a source of electron density for reaction with electrophiles. Have a general understanding of electrophiles as Lewis acids and know relevant examples. Be able to draw a generalized alkene addition reaction using a generic E-Nu reagent. |
| 8.2 | Be able to write a general reaction for the addition of a hydrogen halide to an alkene. Recognize that addition of hydrogen halides to alkenes constitutes a method for synthesis of alkyl halides. Understand the theoretical basis for the most general statement of Markovnikov's rule. Be able to apply it to the addition of any E-Nu reagent to an alkene. Understand the meaning of the term regioselective. Note that carbocation rearrangements are possible. Note that for HBr an exception to Markovnikov addition is possible (Section 8.2D). That is, know the consequences with respect to regiochemistry of using peroxides during addition of HBr to an alkene (anti-Markovnikov addition). Be aware that the mechanism involves radicals (species wth unpaired electrons) instead of ionic intermediates like we have seen thus far, and that we will study mechanisms involving radicals in Chapter 10. |
| 8.3 | Know the stereochemical outcome of addition to alkenes when a carbocation is involved and understand the theoretical basis (the nature of the carbocation intermediate). Also recognize the possibility for carbocation rearrangements (see section 7.8). |
| 8.4 | Understand the addition of cold sulfuric acid to alkenes within the context of the general mechanism for addition of E-Nu reagents to alkenes. |
| 8.5 | Know the acid-catalyzed hydration of alkenes and be able to draw a detailed mechanism for this reaction. Note the regiochemistry of acid-catalyzed hydration. Understand hydration of alkenes within the context of equilibrium reactions and its converse reaction (dehydration of alcohols). Recognize alkene hydration as a method for the synthesis of alcohols. |
| 8.6 | Be able to synthesize an alcohol using the oxymercuration-demurcuration protocol. Know its benefits (lack of molecular rearrangements) and regiochemistry (Markovnikov). Recognize the potential for ether synthesis by making the solvent nucleophile an alcohol instead of water (solvomercuration-demurcuration). |
| 8.7-8.9 | Know the reaction conditions for the hydroboration-oxidation synthesis of alcohols [1) BH3:THF, 2) H2O2, OH-]. Know the stereochemistry for the overall addition of the hydrogen and hydroxyl group (syn) and the regiochemistry (anti-Markovnikov). Recognize hydroboration-oxidation as a synthetic compliment to oxymercuration-demurcuration with respect to regiochemistry. |
| 8.10 | Know the relative regiochemistry, stereochemistry, and limitations of each the three methods for synthesizing of alcohols presented in Sections 8.5-8.9 . |
| 8.11 | Recognize protonolysis of alkylboranes as a method for hydrogenation and for introducing deuterium into a compound. |
| 8.12 | Be able to write a three-dimensional mechanism for halogen (Br2, Cl2) addition to an alkene. |
| 8.13 | Understand the stereochemical consequences in the mechanism for halogen addition to E and Z alkenes. Be able to determine the stereochemical form of the products based on the structure of the starting alkene. Understand what is meant when a reaction is said to be stereospecific. |
| 8.14 | Know how halohydrins are prepared and understand the mechanism for their synthesis as a variation on the theme of halogen addition to alkenes with participation of a nucleophilic solvent. |
| 8.15 | Know some methods for making carbenes and how to use them to prepare cyclopropane compounds from alkenes. |
| 8.16 | Know how to prepare 1,2-diols from alkenes using OsO4. Recognize the stereospecific aspect of this reaction (syn 1,2-dihydroxylation). Cold KMnO4 can also be used for syn 1,2-dihydroxylation. Note that catalytic methods exist for syn 1,2-dihydroxylation. These Nobel Prize-winning methods are not only asymmetric, but use less osmium, which make them less hazardous to the environment. |
| 8.17 | Know the oxidative cleavage reactions of alkenes using either hot KMnO4 or ozone (O3), including conditions and the specific form of products obtained (aldehydes. ketones, carboxylic acids). Be able to think retrosynthetically with regard to what reaction conditions could be used to prepare a given compound. |
| 8.18 | Know the addition reactions of halogens to alkynes, noting that reaction with either one or two molar equivalents of reagent is possible with an alkyne (as compared with an alkene). |
| 8.19 | Note the regioselectivity of addition of one or two molar equivalents of a hydrogen halide to an alkyne. |
| 8.20 | Note that carboxylic acids can be prepared by oxidative cleavage of alkynes. |
| 8.21 | Place all of the reactions in this chapter (and from previous chapters) within the context of an ability to use them to synthesize molecules by a series of reactions. Practice retrosynthetic analysis by looking for functional groups and carbon-carbon bond disconnections that you now know how to prepare by various reactions. That is, consider how reactions can be used to form carbon-carbon bonds, interconvert functional groups, and control stereochemistry and/or stereochemistry. Note how the stereochemistry and regiochemistry of each reaction must be considered in the planning of any synthesis. |
| Summary and Review Tools |
Use the Mechanism Review tool to organize your knowledge of electrophilic reagents used in alkene addition reactions, including their polarity, the transition state involved for each, and the subsequent regiochemistry and stereochemistry that result from these factors. Use the Synthetic Connections box to review reactions by which you can now synthesize or interrelate various types of compounds and functional groups. Consider stereochemical and/or regiochemical outcomes that may be relevant to some transformations. Use the Key Terms and Concepts list as a self-test for your understanding of the listed terms. |
| Section | Goals |
|---|---|
| 9.1 | Know the definition of spectroscopy. |
| 9.2 | Understand the general properties of waves (wavelength, frequency, units used in describing waves). Gain a general appreciation for wavelength and the relative energy of various regions of the electromagnetic spectrum. |
| 9.3A,B | Read for background and general understanding of the basis for nuclear magnetic resonance (NMR). |
| 9.3C | Understand the meaning of "chemical shift", the reason for differences in chemical shift from one nuclear environment to another, and the use of the terms "upfield" and "downfield". Understand interpretation of chemical shift with respect to number of peaks in an NMR spectrum and the number of different types of hydrogens in a molecule. |
| 9.3D | Understand the interpretation of integral curves, i.e., the correspondence of peak area with the number of hydrogens producing a given signal. |
| 9.3E | Know what is meant by "signal splitting" (the interpretation of which will be explained in later sections). |
| 9.4 | Read for general understanding. |
| 9.5 | Recognize that nuclei can be shielded or deshielded from the applied magnetic field in an NMR spectrometer by the influence of electron density and circulating electrons near a given nucleus. As a result, the position of peaks for nuclei in various environments fall in predictable chemical shift regions. (see Figure 9.13, which is also found inside the back cover) |
| 9.6 | Be able to use Figure 9.13 to predict the chemical shift of proton NMR signals in molecules. Know that TMS is the reference standard (with a chemical shift of zero) for the chemical shift scale. |
| 9.7 | Be able to identify chemically equivalent (and therefore chemical shift equivalent, or homotopic) nuclei in NMR spectra. Be able to identify enantiopic and diastereotopic hydrogens. |
| 9.8 | Using the n+1 rule for signal splitting, be able to predict the number of peaks in an NMR spectrum for a given set of hydrogens, bearing in mind the relevance of chemically equivalent (homotopic), enantiotopic, and diastereotopic hydrogens. Be able to work backwards from spin-spin splitting patterns in a spectrum to determine how many hydrogens are neighboring the hydrogens giving rise to the signal being interpreted. Understand the reciprocity of coupling constants. |
| 9.9 | Know that rapid conformational change leads to a signal that is a weighted average of the environments experienced by a given nucleus. Know that spin-spin splitting is usually not observed between hydrogens on O and N atoms (e.g. alcohols, amines, and carboxylic acids) and the hydrogens on carbon atoms adjacent to these groups, due to chemical exchange by virtue of their acidity. |
| 9.10 | Be able to interpret 13C NMR spectra (i.e., elucidate a structure) using chemical shift correlations (see Figure 9.27, which is also found inside the back cover) and DEPT information. Be able to predict a 13C NMR spectrum for a compound having a given structure. |
| 9.11 | Know how to interpret COSY and HETCOR two-dimensional NMR spectra. |
| 9.12 | Note the different axes used in mass spectra, as compared with IR and NMR, and understand their meaning. |
| 9.13 | Be able to write a general equation for electron impact ionization and understand the process in a general sense. Know that fragmentation can occur. Know that mass spectrometers sort ions of differing mass to charge ratios (m/z). Note the variety of ion sorting methods used in mass spectrometers having different designs. |
| 9.14 | Understand what the molecular ion (M+) and base peak are in a mass spectrum. Understand that M+1 peaks (and M+2 peaks) are caused by the presence of isotopic nuclei in molecules. |
| 9.15 | Know how to use the M+1 peak in an electron impact mass spectrum to calculate the molecular formula for a compound. |
| 9.16 | Be able to draw fragmentation equations (showing single electron movements with single-barbed arrows). Know that electron impact ionization occurs most easily by dislodging a nonbonding or pi electron, and that fragmentation usually occurs at adjacent bonds. Know that fragmentation is especially likely when the cleavage forms a relatively stable carbocation (e.g. an allylic cation or acylium ion). Know that fragmentation involving cleavage of two bonds can also occur if a hydrogen atom can be transfered and/or if a cyclic transition state can occur (e.g. the retro-Diels Alder or McLafferty rearrangements). |
| 9.17 | Know the meaning of the acronym GC/MS and that it is a very powerful and widely used technique for separation and identification of compounds. |
| 9.18 | Know that mass spectrometry can be done with nonvolatile and very large molecules (e.g. polymers and biomolecules) using "soft" ionization techniques such as electrospray ionization (ESI), matrix-assisted laser desporption ionization (MALDI), and other techniques. |
| Summary and Review Tools |
Use the Concept Maps to highlight the relationships among concepts in each type of spectroscopy and for an overall summary and review. Use Figures 9.13 and 9.27 (also inside the back cover) for reference regarding NMR chemical shifts. Use the Key Terms and Concepts list as a self-test for your understanding of the listed terms. |
| Section | Goals |
|---|---|
| 10.1 | Understand the difference between heterolytic and homolytic bond cleavage with regard to respective formation of ionic and free radical reaction intermediates. Be able to use single-barbed arrows to clearly and accurately show single electron movements in reactions of radicals. Know the common ways of producing radicals. Recognize the importance of radicals in industry and biological processes. |
| 10.2 | Be able to calculate the overall enthalpy change (Delta H, or heat of reaction) for bond forming and/or bond breaking steps, given the bond dissociation energies (DHo) for each pertinent species. Know whether to apply a positive or negative mathematical sign to each bond dissociation energy used in an enthalpy calculation. Know the relative order of alkyl radical stability (3o > 2o > 1o). |
| 10.3 | Recognize the possibility for both multiple halogen substitution and the formation of constitutional isomers in free radical halogenation of alkanes. Note that use of an excess of alkane with respect to the halogen can lead to primarily mono-substitution (although without selectivity for chlorination). Recognize the importance of symmetry in determining the number of possible products. Know the relative reactivites of chlorine and bromine, i.e., that chlorine is more reactive but less selective whereas bromine is less reactive but more selective. |
| 10.4 | Know, as a simple example to be extended to other compounds later, the chain reaction mechanism for free radical halogenation of methane, including the chain initiating, chain propagating, and possible chain terminating steps. Understand that the sum of the chain propagating steps is equivalent to the overall reaction equation. |
| 10.5 | Know how to calculate the overall Delta H for a reaction by summing the Delta H for the chain propagation steps. Read for general understanding the explanations involving transition state theory. Note that 1) radical chlorination and bromination are energetically feasible, 2) radical fluorination is very exergonic (so much so as to be impractical outside of industrial laboratories), and 3) radical iodination is energetically unfavorable and therefore not feasible. |
| 10.6 | Recognize that chlorination is relatively non-selective regarding the position of substitution, and therefore typically leads to a mixture of products. Consider free radical bromination as a synthetically useful reaction due to its relative selectivity as compared to chlorination. |
| 10.7, 10.8 | Know the hybridization of a carbon radical and be able to draw a three-dimensional dash-wedge structure for a carbon radical intermediate. Understand the ramifications of this structure with regard to radical reactions that involve or produce a stereogenic center. Be able to predict whether a free radical reaction will lead to stereoisomers, and if so, whether enantiomers or diastereomers would be formed. |
| 10.9 | Understand the mechanistic basis for anti-Markovnikov addition of HBr to alkenes in the presence of peroxides. Recognize the utility of this method as a regiochemical complement to HBr addition to alkenes in the absence of peroxides (Markovnikov addition). |
| 10.10 | Know the general mechanism for free radical chain-growth polymerization of alkenes. Consider the specific examples of polyethylene, polystyrene, and others listed. See the Special Topic on chain-growth polymers for further information. |
| 10.11 | Recognize the role of radicals such as superoxide and nitric oxide in some biological processes. Note the relevance of chain reactions in combustion, autoxidation (air oxidation), and reactions of halogen radicals with ozone. Consider the example of hydroperoxide formation shown by autoxidation of a polyunsaturated fat, and the role of antioxidants in scavenging radicals. |
| Summary and Review Tools |
Use the Mechanism Review to consider key aspects of radical halogenation, anti-Markovnikov addition of HBr, and radical polymerization. Use the Key Terms and Concepts list as a self-test for your understanding of the listed terms. |
Although there are many new reagents and reactions in this chapter, there is little new regarding general mechanisms and reaction types. Attempt to place each new reaction within the context of a general mechanistic class you have already learned, i.e. addition reactions of alkenes (oxymercuration-demurcuration, hydroboration-oxidation, epoxide synthesis), nucleophilic substitution (tosylates, mesylates, alkyl halide and ether synthesis from alcohols, and epoxide ring opening), and general acid-base principles.
| Section | Goals |
|---|---|
| 11.1 | Be able to name alcohols by the IUPAC system. Be able to name ethers using common functional class names for simple ethers or IUPAC substitutive names for more complicated ethers. Be able to distinguish a phenol from an alcohol, and recognize benzyl and allyl alcohols/ethers. Be able to write the general formula (using R groups) for an alcohol or ether. |
| 11.2 | Understand the general differences in terms of intermolecular forces between alcohols and ethers. |
| 11.3 | Read for general information and appreciation of the practical relevance of some alcohols and ethers. |
| 11.4 | Recall and review (from Chapter 8) the various methods for alcohol synthesis by hydration of alkenes: acid-catalyzed hydration, oxymercuration-demercuration, and hydroboration-oxidation. Recall the limitations of acid-catalyzed hydration (carbocation rearrangements, etc.). Be able to synthesize an alcohol using the oxymercuration-demurcuration protocol. Recall the benefits of oxymercuration-demercuration (lack of molecular rearrangements) and regiochemistry (Markovnikov). Recognize the potential for ether synthesis by making the solvent nucleophile an alcohol instead of water (solvomercuration-demurcuration). Recall the reaction conditions for synthesis of alcohols by hydroboration-oxidation [1) BH3:THF, 2) H2O2, OH-]. Know the stereochemistry for the overall addition of the hydrogen and hydroxyl group (syn) in hydroboration-oxidation and the regiochemistry (anti-Markovnikov). Recognize hydroboration-oxidation as a synthetic compliment to oxymercuration-demurcuration with respect to regiochemistry. |
| 11.5 | Recall the essential properties of alcohols: the alcohol oxygen is moderately nucleophilic and weakly basic, the alcohol hydroxyl group is a poor leaving group unless first protonated or converted into a leaving group by formation of some type of sulfonate ester (e.g., a tosylate, mesylate, triflate, see Section 11.10). |
| 11.6 | Recall that alcohols are weakly acidic and can form strong alkoxide bases/nucleophiles upon deprotonation by a stronger base (e.g. NaH) or an alkaline earth metal (Na or K). |
| 11.7 | Note the common theme presented here for the following sections, regarding conversion of an alcohol hydroxyl group to a good leaving group in preparation for C-O bond cleavage. |
| 11.8 | Recognize that alcohols can be converted to alkyl halides by reaction with the appropriate HX. Understand the mechanism as beginning with a simple acid-base reaction to prepare the alchohol hydroxyl group as a leaving group, followed by nucleophilic substitution. |
| 11.9 | Know PBr3 and SOCl2 as the preferred reagents for conversion of 1o and 2o alcohols to alkyl bromides and chlorides, respectively. |
| 11.10 | Know the reaction conditions for forming tosylates and mesylates and
the structures of the products, including those written with the Ts or Ms
abbreviation. Know that alkyl sulfonates can be used as an indirect method
for accomplishing SN2 nucleophilic substition of the hydroxyl
group in an alcohol ( |
| 11.11 | Recognize the intermolecular dehydration of alcohols as a method for synthesis of symmetrical ethers. Understand the mechanism as simply applications of acid-base and nucleophilic substitution reaction mechanisms. Know how to accomplish a Williamson ether synthesis (11.15B) and recognize it's limitations according to the requirement that it be an SN2 reaction. Note the use of alkoxymercuration-demercuration as a method for ether synthesis. Note the use of tert-butyl ethers and silyl ethers as protecting groups. |
| 11.12 | Understand the reactions of ethers with acids as protonation to form a leaving group followed by nucleophilic substitution to form the respective products. |
| 11.13 | Know the general structure of an epoxide (oxirane) and the reagents used for their formation from alkenes (peroxy carboxylic acids, i.e. RCOOOH or RCO3H). Know the stereochemistry of oxygen addition (syn, by default, with retention of the original alkene geometry). |
| 11.14 | Understand the principles of acidic or basic ring-opening of epoxides, and know the mechanistic/regiochemical implications of each (e.g. regiochemistry of attack by the nucleophile). |
| 11.15 | Recognize epoxidation followed by hydrolysis (acidic or basic) as a means for anti 1,2-hydroxylation of alkenes. |
| 11.16 | Note the use of crown ethers as phase transfer reagents and the biochemical significance of ionophore antibiotics (11.20B). |
| 11.17 | Use this section to tie together the various reactions and their stereochemical and regiochemical ramifications. Consider how each reaction could be used in synthesis problems. Categorize reactions according to the types of functional groups each one allows you to form, the functional groups required in the starting materials, and the stereochemical/regiochemical control each reaction may exhibit. |
| Summary and Review Tools |
Use the Key Terms and Concepts list as a self-test for your understanding of the listed terms. Use the Synthetic Connections scheme to review the toolbox of reactions and methods you have available to synthesize or interrelate various types of compounds and functional groups. Consider stereochemical and/or regiochemical outcomes that may be relevant to some transformations. |
This chapter is largely devoted to methods for the interconversion of
functional groups by oxidation and reduction and the formation of carbon-carbon
bonds by reactions of organometallic reagents. Work toward expanding your
synthetic repertoire and developing your retrosynthetic analysis skills.
| Section | Goals |
|---|---|
| 12.1 | Know the structure of the carbonyl group with respect to hybridization, bond angles, and C==O polarity. Note the general reaction for nucleophilic addition to carbonyl groups. Especially relevant to this chapter is the nucleophilic addition of hydride and organometallic carbanion-like reagents. |
| 12.2 | Know the general definitions of oxidation and reduction as applied to organic compounds (with regard to hydrogen and oxygen content). Know the relative order of oxidation state when comparing alcohols, aldehydes and ketones, carboxylic acids, and esters. |
| 12.3 | Be able to draw the structure of each respective product resulting from lithium aluminum hydride (LiAlH4, or LAH) reduction of any aldehyde, ketone, carboxylic acid or ester. Recognize the lesser reducing power of sodium borohydride (NaBH4) as compared to LiAlH4. Know the functional groups that can be reduced by NaBH4 and be able to draw structures for the resulting products. Note the common characteristic in these reactions of hydrogen with an electron pair (i.e. hydride) attacking a carbonyl carbon. |
| 12.4 | Know how to prepare an aldehyde from a 1o alcohol using PCC (pyridinium chlorochromate). Know how to prepare a carboxylic acid from a 1o alcohol using basic KMnO4 followed by acidification. Know how to prepare a ketone from a 2o alcohol using H2CrO4 (chromic acid). Recognize that 3o alcohols cannot be oxidized. |
| 12.5 | Understand the general polarity of carbon-metal bonds and the potential for the carbon in an organometallic compound to be strongly nucleophilic or basic. |
| 12.6 | Know how to prepare organolithium (RLi) compounds and organomagnesium compounds (RMgX, Grignard reagents). |
| 12.7 | Know the products that result when organolithium and organomagnesium compounds react with a) compounds containing acidic (even relatively weakly acidic) hydrogens, b) epoxides, and c) carbonyl compounds. Understand these reactions as being due to either the strongly basic or powerfully nucleophilic nature of the RLi and RMgX reagents. Note that RLi and RMgX reagents cannot be used for SN1 and SN2 nucleophilic substitution reactions because they would primarily cause E2 elimination by their strongly basic character. |
| 12.8 | Know how to synthesize 1o, 2o, or 3o alcohols from the appropriate aldehyde or ketone by a Grignard reaction. Note, as an aside, the reaction of two molar equivalents of a Grignard reagent with an ester. |
| 12.8A | Study the retrosynthetic and synthetic methodologies that become possible using Grignard reactions and other reactions in your repertoire. Practice synthesis and retrosynthetic analysis on a variety of target molecules. Become versatile with functional group interconversions and C-C bond forming reactions. |
| 12.8B, C and D | Understand that limitations exist (Section 12.8B) for the use of Grignard and organolithium reagents when other functional groups are present that would react competitively or instead of the desired reaction. Note the parallel reactivity of RLi and Grignard reagents (Section 12.8C). Note that sodium alkynides also undergo addition reactions to carbonyl groups of aldehydes and ketones (Section 12.8D). |
| 12.9 | Know how to prepare lithium dialkylcuprate reagents from alkyl halides. Know the scope and limitations for using lithium dialkylcuprates for carbon-carbon bond forming reactions. |
| 12.10 | Understand, in general, what a protecting groups is and how one might be used in the course of a reaction that involves a functional group incompatible with necessary reagents. Review the use of tert-Butyl ethers and silyl ethers as protecting groups for alcohols (Sections 11.11D and 11.11E). |
| Summary and Review Tools |
Use the Synthetic Connections schemes to review synthetic methods involving carbonyl reduction, alcohol oxidation, and carbon-carbon bond forming reactions. Use the Key Terms and Concepts list as a self-test for your understanding of the listed terms. |
| Section | Goals |
|---|---|
| 13.1 | Understand the general structures possible for the following three types of conjugated systems: allylic radicals, allylic cations, and conjugated alkenes. |
| 13.2 | Know the general reaction for allylic halogenation. Be able to write the general reaction conditions for allylic chlorination (Sect. 13.2A). Recall the steps of radical reaction mechanisms and apply them to radical allylic substitution. Be able to write reactions for allylic bromination using NBS (Sect. 13.2B). |
| 13.3 | Understand the molecular orbital representation of the allyl radical and the accompanying rationale for its relative stability. Be able to draw resonance structures of an allylic radical. |
| 13.4 | Understand the molecular orbital representation of the allyl cation and the accompanying rationale for its relative stability. Be able to draw resonance structures for an allylic cation. |
| 13.5 | Refine your understanding of resonance structures (first introduced in Section 1.8). Recognize that individual resonance forms of a molecule do not exist, but that the true form of a molecule is a hybrid of the contributing resonance structures. Be able to draw resonance structures that follow the rules prescribed in this section. Be able to evaluate the relative contribution of a given resonance form to that of the overall resonance hybrid. |
| 13.6 | Be able to provide complete IUPAC names for polyunsaturated hydrocarbons. Be able to classify specific examples as being conjugated, cumulated, or isolated polyunsaturated compounds. |
| 13.7 | Become familiar with the structure of 1,3-butadiene with respect to its two most likely conformations and its molecular orbital representation. |
| 13.8 | Note that conjugated unsaturated systems are thermodynamically more stable than corresponding isolated unsaturated systems. |
| 13.9 | Know the mathematical relationship between absorbance, molar absorptivity, concentration, and path length. Understand that spectroscopy of organic molecules in the ultraviolet and visible (UV/Vis) wavelength regions is typically due to energy transitions of nonbonding (n) and pi bonding electrons. Recognize that the energy of these transitions decreases with increasing conjugation in the molecule. Note that an understanding of molecular orbital (MO) theory is very helpful in understanding UV/Vis spectroscopic absorptions. Recognize that UV-Vis spectroscopy is an important analytical tool in biochemical and environmental studies. |
| 13.10 | Recognize the possibility of 1,2 and 1,4 electrophilic addition pathways in conjugated dienes. Understand that the 1,2 and 1,4 addition products result from a common intermediate, i.e. an allylic cation. Be able to write a mechanism depicting formation of both 1,2 and 1,4 addition products. Understand the terms kinetic control and thermodynamic or equilibrium control (Sect. 13.10A). Be able to interpret, in terms of these effects, the 1,2 to 1,4 product ratio resulting from addition to a conjugated system at high and low temperature. |
| 13.11 | Know the general depiction of a Diels-Alder reaction and be able to classify each reactant as either the diene or dienophile. Recognize the stereospecific aspects of the Diels-Alder reaction, in terms of syn addition, diene reaction from the s-cis conformation, and the preference for endo products. Be able to incorporate these stereochemical attributes when writing the structure of Diels-Alder adducts. Be able to recognize when a target molecule could be synthesized by a Diels-Alder reaction, and to take advantage of the stereospecificity of the Diels-Alder reaction when appropriate in planning an organic synthesis. |
| Summary and Review Tools |
Use the Concept Map to highlight relationships between concepts and for an overall summary and review of conjugated systems and their reactivity. Use the Key Terms and Concepts list as a self-test for your understanding of the listed terms. |
| Section | Goals |
|---|---|
| 14.1 | Note the history of discovery of aromatic compounds and the role of benzene as the parent in this family. Note the modern meanings of the classifications aliphatic and aromatic. |
| 14.2 | Develop facility in naming aromatic compounds as derivatives of benzene (e.g. methylbenzene) and for some, as aromatic compounds with common names (e.g. toluene). Be able to correctly apply the prefixes ortho, meta, and para when naming disubstituted benzenes, as well as numbers to designate substituent positions in di- and higher substituted benzenes. Gain clear understanding of the terms phenyl (and its abbreviations) and benzyl as structural moieties. |
| 14.3 | Recognize the unique stability of benzene under various reaction conditions in which ordinary unsaturated compounds would react. Note, as an exception to unsaturated systems we have studied thus far, that benzene can undergo substitution reactions, although it is by a mechanism to be covered in Chapter 15 (electrophilic aromatic substitution). |
| 14.4 | Gain facility in representing benzene and related compounds using bond-line structural formulas. Note the equivalency of the two possible resonance forms that can be drawn for the ring in benzene and related compounds. |
| 14.5 | Recognize the special stability of benzene as indicated by thermodynamic comparison of actual hydrogenation to cyclohexane with hypothetical hydrogenation of cyclohexatriene. |
| 14.6 | Further secure an understanding of the bond-line representations of benzene as being two equally contributing resonance forms, and that a hybrid structure can be drawn using a circle within the hexagon instead of three double bonds alternating with three double bonds. Equally important, gain an appreciation for the molecular orbital representation for benzene as having six sp2 hybridized carbons whose individual p orbitals overlap to form continuous pi electron molecular orbitals above and below the plane of the carbon ring (Sect. 14.6B). |
| 14.7 | Be able to apply the Huckel 4n+2 rule to characterize as aromatic or not any planar cyclic compound where each atom has a p orbital. Recognize the applicability of this system for characterizing annulenes (Sect 14.7A). |
| 14.7B | Note that NMR spectroscopy confirms the identical nature of the hydrogen atoms in benzene. Revisit the concepts of shielding and deshielding in NMR spectroscopy (Section 9.5) and incorporate an understanding of the aromatic nature of benzene to rationalize the downfield chemical shift of the benzene hydrogens (specifically the effect called ring current). Similarly, consider the effect of ring current on the chemical shift of internal hydrogens in large-ring aromatic compounds. |
| 14.7C | Recognize that some planar, cyclic ions can be classified as aromatic by the Huckel rule. Be able to characterize cyclic ionic compound as being aromatic or not. Note consistency of the molecular orbital representation of aromatic ions with molecular orbital depictions of neutral aromatic compounds. |
| 14.7D | Note the definitions of antiaromaticity and nonaromaticity, as well as examples of each. |
| 14.8A | Recognize the existence of polycyclic benzenoid aromatic compounds. Understand the rationale behind "peripheral" aromaticity observed in some polycyclic aromatic compounds, e.g. pyrene. |
| 14.8B | Recall the examples of nonbenzenoid aromatic compounds given thus far, including aromatic ions, and use these to understand the polar nature of azulene. |
| 14.8C | Note the intriguing architecture of fullerene compounds and the phenomenal potential for practical uses in materials science, nanotechnology, and biotechnology. |
| 14.9 | Be able to determine whether a given heterocyclic compound is or is not aromatic. |
| 14.10 | Note the pervasive importance of aromatic compounds in biochemistry, e.g. their roles in aromatic amino acid and nucleic acid structure. Also note examples of toxic aromatic compounds. |
| 14.11 | Understand the origin of proton and carbon NMR chemical shifts in spectra of aromatic compounds on the basis of both aromaticity, ring current, and the effect of substituents on electron density distribution. Know the characteristic IR frequency range for C-H stretching in aromatic compounds and note that substitution patterns in substituted benzene compounds can be indicated by certain low frequency IR absorptions by the ring. Note typical characteristics of UV-Vis and mass spectra of aromatic compounds. |
| Summary and Review Tools |
Use the Concept Map as an overall summary and review of concepts related to aromatic systems, aromatic compounds, and their reactivity. Use the Key Terms and Concepts list as a self-test for your understanding of the listed terms. |