Topic Sequence and Emphasis Variability of Selected Organic

In the Classroom

Topic Sequence and Emphasis Variability of Selected Organic Chemistry Textbooks Justin B. Houseknecht Department of Chemistry, Wittenberg University, Springfield, Ohio 45501 [email protected]

Textbook selection is one of the more important decisions that instructors of organic chemistry make each year. This Journal routinely carries reviews of organic textbooks (1-3); however, these avoid direct comparisons between textbooks. Papers have been published comparing how different textbooks treat particular topics (4) or analyzing student feedback on a few chapters from several different books (5). However, it has been 26 years since a more comprehensive survey has been published (6). Therefore, thousands of organic instructors have to take the time each year to complete their own evaluation of the available textbooks, or choose to just continue using the book they have used for the past decade. The purpose of this paper is to provide instructors more ready access to the data they need to choose the most appropriate textbook for their course. The nine textbooks included in this analysis were the most popular ones according to the search results of Amazon.com (7) and BarnesandNoble.com (8) as of September 2009. It is not the intent of this article to make judgments concerning the relative merit of various textbooks, their organization, the quality of problems presented, or the degree of accuracy in the mechanisms presented. The information presented will be the most relevant for the next 2 to 3 years before new editions are released, but should remain valuable for several years thereafter because changes between editions are typically incremental.

The number and type of problems covering aromatics, aldehydes, and ketones, and their reactivity involving the carbonyl carbon were also examined. For multipart questions, each part was counted as a separate question. These were extracted from the chapters on aromatics (typically Chapter 2) and aldehydes and ketones (present in most texts). The chapter on naming that included aldehydes and ketones was also examined in Hornback's textbook (12). The textbook by Smith (14) contains two chapters with problems covering aldehydes and ketones; both chapters were analyzed. Problems covering the reactions of heteroaromatics, phenols, and nucleophilic aromatic substitution were not included in this study. The problem types and detailed results are provided in the online supporting information, Tables S4 and S5. The reactions presented in the chapters on aromatics and the chapter(s) on carbonyl carbon reactions of aldehydes and ketones were also assessed. It was determined whether each reaction was presented within the textbook (not just the chapters under investigation), whether any mechanistic detail was presented within the textbook, and whether a complete mechanism was presented within the textbook. The reaction types and results are listed in the online supporting information, Tables S6 and S7.

Methods and Definitions

Organic Chemistry Topics

The subject sequencing in nine texts was examined. These nine textbooks are referred to throughout this paper as follows: Brown et al., 5th edition (9); Bruice, 5th edition (10); Carey, 9th edition (11); Hornback, 2nd edition (12); McMurry, 7th edition (13); Smith, 2nd edition (14); Solomons and Fryhle, 9th edition (15); Wade, 6th edition (16); and Vollhardt and Schore, 5th edition (17). The subjects were broken down into 19 organic chemistry topics, 21 organic chemistry concepts and skills, and 7 biological topics. The topics are typical methods for organization of organic chemistry; concepts and skills are particular ways of thinking that students are typically asked to master (or at least be aware of); and the topics of biological interest chosen are common examples that show the relevance of organic chemistry to biological systems. The definitions of each particular topic are given in the online supporting information (Tables S1-S3) with a brief description of how the page of introduction was determined. The order of subjects within the topics, concepts and skills, and biological topics sections was determined by the average page of introduction of each subject in the textbooks examined. Most of this information was found in the tables of content, but for several topics, it was necessary to look through indices or read the book page by page.

Figure 1 and Table S8 (in the online supporting information) show the percentage of the way through each textbook that topics are introduced. Topics that are introduced very early in most textbooks appear lower in the figure and those that are introduced later appear higher in the figure. Topics that were not discussed appear as being introduced on the final page of the book (at 100%). Several of the results shown in Figure 1 bear further explanation. First, of the nine textbooks examined, six introduce organic reactivity with the reactions of alkyl halides, substitution, and elimination. The textbooks by Brown et al. (9), Bruice (10), and McMurry (13) introduce the reactions of alkenes as the first major class of organic reactivity. Several of these textbooks do contain at least a brief introduction to free radical halogenation of alkanes very early in the text, but this was not examined in detail. Significant variability was observed in the placement of many of the other topics, but not all. Spectroscopy is introduced at around 40% of the way through the book in eight of the nine textbooks, although the textbook by Solomons and Fryhle (15) introduces spectroscopy very early with infrared spectroscopy in the introduction to the functional groups chapter.

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Results and Discussion

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Vol. 87 No. 6 June 2010 pubs.acs.org/jchemeduc r 2010 American Chemical Society and Division of Chemical Education, Inc. 10.1021/ed100168t Published on Web 04/23/2010

In the Classroom

Figure 1. Comparison of the placement of topics within the textbooks examined. Specific data on each type of spectroscopy can be found in the supporting information. Topics that were not discussed appear as being introduced on the final page of the book (at 100%).

The introduction of Grignard and organolithium reagents varies substantially, with McMurry (13) and Vollhardt and Schore (17) introducing them with the reactions of alkyl halides, and most other authors waiting until discussions of the synthesis of alcohols or reactions of aldehydes and ketones. All of the textbooks examined introduce the reactivity of aromatics before that of carbonyl compounds. Most discuss aldehydes and ketones before carboxylic acids and their derivatives, though Bruice (10) reverses this order and Smith (14) discusses aldehydes and ketones between the discussion of carboxylic acids and the discussion of their derivatives. There is more variability in the placement of R-carbonyl reactions. Carey (11), Vollhardt and Schore (17), and Solomons and Fryhle (15) introduce R-carbonyl reactions prior to carboxylic acids and their derivatives, whereas Brown et al. (9), Bruice (10), Hornback (12), McMurry (13), Smith (14), and Wade (16) introduce carboxylic acids and their derivatives first. Amines were a difficult topic for which to designate a page of introduction because all textbooks discuss the reactivity of amines repeatedly before the actual amines chapter. Therefore, the criterion used was introduction of amine nomenclature. Figure 1 suggests that Hornback (12) introduces amines far earlier than other authors, but this is true only of the nomenclature of amines, not their reactivity. Finally, the coverage of modern organometallic reactions such as Heck, Stille, and olefin metathesis varies from quite early in Bruice (10), Carey (11), and Vollhardt and Schore (17), to later in Brown et al. (9), and Smith (14), to not at all in Hornback (12), McMurry (13), Solomons and Fryhle (15), and Wade (16). Organic Chemistry Concepts and Skills Figure 2 shows the placement of the important concepts and skills that most organic students are expected to master. (These placements are also tabulated in Table S9 in the online supporting information.) Three concepts that are not shown in Figure 2 are Lewis dot structures, structure-activity relationships, and the bond-arrow formalism. The pages of introduction were recorded for these concepts in Table S9 in the online supporting

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information, but to simplify Figure 2, they were omitted because all textbooks examined introduce these concepts within the first few pages. Eight of the nine textbooks also introduce molecular orbital theory in the first chapter in the discussion of bonding; Smith (14) does not discuss molecular orbital theory until the chapter on dienes, much later in the textbook. Other topics introduced much later in some textbooks include: radical reactions in Hornback (12), Diels-Alder reactions in Brown et al. (9) and in Hornback (12), and polymerization in Brown et al. (9), Bruice (10), and Hornback (12). The skills of retrosynthetic analysis and multistep synthesis are typically introduced in close proximity to one another. Hornback (12), Solomons and Fryhle (15), and Vollhardt and Schore (17) introduce both concepts in the same chapter, while the other textbooks introduce retrosynthesis in an earlier chapter than multistep synthesis. A majority of the textbooks surveyed introduce stereoselectivity within the first 15-30% of the book, but Hornback (12), McMurry (13), and Wade (16) do not discuss it at all. The topic of green chemistry is omitted from three textbooks: Brown et al. (9), Bruice (10), and Wade (16). Similarly, combinatorial chemistry is omitted from several textbooks: Brown et al. (9), Bruice (10), Hornback (12), Smith (14), Solomons and Fryhle (15), and Wade (16). Biological Topics The most striking result of this survey was how late in the textbook most authors discuss topics of biological interest: see Figure 3, and Table S10 in the online supporting information. The most significant exception to this is the introduction of Fischer projections to describe the chirality of biological molecules. Most textbooks introduce these structures in the chapter on stereochemistry, but McMurry (13) and Smith (14) do not do so until much later in the chapter on carbohydrates. Most authors also postpone the discussion of steroids until near the end of the textbook; however, Vollhardt and Schore (17) introduce steroidal structure very early in the chapter on cycloalkane conformations. They do not, however, discuss steroids in a later chapter as the other textbooks do. Finally, the topic of peptide synthesis is reserved

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Figure 2. Comparison of the placement of concepts and skills within the textbooks examined. Specific data on Lewis structures, structure-reactivity relationships, and bond-arrow formalism can be found in the supporting information. Topics that were not discussed appear as being introduced on the final page of the book (at 100%).

Figure 3. Comparison of the placement of biological topics within the textbooks examined.

for the chapter on amino acids and peptides in most textbooks, but Smith (14) and Solomons and Fryhle (15) have a substantial introduction to peptide synthesis in the chapter on carboxylic acid derivatives. Problems for Students To Work The number and type of problems in each book covering aromatics is shown in Figure 4 and tabulated in Table S4 (in the online supporting information). The total number of problems ranged from 233 in Solomons and Fryhle (15) to 355 in Bruice (10). Predict-the-product questions predominate in the textbooks by Carey (11), Hornback (12), and Wade (16) containing roughly 30% more problems than the others. The Brown et al. (9) textbook clearly underemphasizes predict-the-product type questions and overemphasizes provide-the-reagent and multistep synthesis questions for this topic relative to the other textbooks. 594


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Figure 4. Comparison of the quantity of problems covering aromatic compounds in the textbooks examined.

The textbooks by Bruice (10) and Carey (11) have a similarly high number of provide-the-reagent questions. McMurry (13) and Vollhardt and Schore (17) have a conspicuously low number of multistep synthesis questions. The textbooks by Bruice (10), Carey (11), Smith (14), and Wade (16) contain more questions about the structure of aromatics and aromaticity than the other textbooks. Four of the authors, including Bruice (10), McMurry (13), Smith (14), and Vollhardt and Schore (17), wrote significantly more problems concerning activating and deactivating groups (kinetics) than the other authors. Similarly, Carey (11), McMurry (13), and Vollhardt and Schore's (17) texts contain more problems concerning directing effects than the others. There is little difference in the number of problems covering naming, mechanism, and explanation in these texts.


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In the Classroom

Figure 5. Comparison of the quantity of problems covering aldehydes and ketones in the textbooks examined. (N.B.: Smith has 189 predict-theproduct questions involving aldehydes and ketones;the scale was reduced to amplify other differences between textbooks.)

The exception is the large number of mechanism questions in the Brown et al. (9) and Wade (16) textbooks. The number and type of problems in each book covering the aldehyde and ketone functional groups is shown in Figure 5 and tabulated in Table S5 (in the online supporting information). The Smith (14) textbook has substantially more (189) predict-theproduct questions than any other text, though the full extent of this is not shown in Figure 5 in order to emphasize other differences between the textbooks. The product prediction questions, along with provide-the-reagents and multistep synthesis questions, predominate in most textbooks. Several textbooks, notably Brown et al. (9), Carey (11), Hornback (12), Smith (14), and Wade (16), clearly have more product prediction questions than the others. These textbooks also tend to have higher numbers of provide-the-reagent and multistep synthesis questions, although Carey (11) is an exception and Hornback (12) has fewer provide-the-reagent questions than the other textbooks. The Bruice (10) textbook also has a large number of provide-the-reagent and multistep synthesis questions. Wade (16) has approximately twice as many structure and mechanism questions as any of the other textbooks in the chapters examined. The other significant outlier with respect to questions about carbonyl structure is Vollhardt and Schore (17), with only two. Finally, the discussion of aldehyde and ketone reactivity sometimes involves either or both kinetic and thermodynamic principles. Four of the textbooks contain questions involving kinetics, namely, Bruice (10), Carey (11), Smith (14), and Vollhardt and Schore (17). These four textbooks, plus Hornback (12) and Wade (16), also contain a number of questions dealing with the position of equilibria in reactions of aldehydes and ketones. Hornback (12) actually contains twice as many questions about equilibria than any of the other textbooks examined. Finally, summation of all data in Figure 5 indicates that most textbooks contain approximately 150-250 questions on aldehydes and ketones. With 441 questions, the Smith (14) textbook is the significant exception to this. Comparison of the results from the aromatics section with those from the aldehydes and ketones may clarify several issues.


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Figure 6. Comparison of the number of reactions, at least partial mechanisms, and full mechanisms discussed in each of the textbooks examined of aromatic compounds and of the carbonyl carbon of aldahydes and ketones.

First, the large number of predict-the-product questions in the Smith (14) textbook covering aldehydes and ketones appears to be an anomaly, at least compared to the questions covering aromatic chemistry. The texts by Carey (11), Hornback (12), and Wade (16) contain more predict-the-product questions than the others in both topics examined. The text by McMurry (13) has conspicuously fewer predict-the-product questions, particularly in the chapter covering the chemistry of aldehydes and ketones at the carbonyl carbon. The text by Hornback (12) contains fewer provide-the-reagent questions in both chapters, but this is somewhat compensated for with an above-average number of multistep synthesis questions. Several texts emphasize structural topics to a greater degree than the others: Bruice (10), Carey (11), and Wade (16). The texts by Brown et al. (9), Hornback (12), Solomons and Fryhle (15), and Wade (16) contain fewer problems covering reactions rates, equilibria, and directing effects in electrophilic aromatic substitution, though Hornback (12) does contain significantly more carbonyl equilibrium questions than any of the other texts. The texts examined contain similar numbers of mechanism


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questions, though some are clearly above average: Brown et al. (9), Wade (16), and Carey (11) contain fewer questions of this type. Similarly, the text by Carey (11) contains fewer questions requiring explanation than the others. Reactions The presence of 15 reactions involving aromatic compounds was determined for each textbook: see Figure 6, and Table S6 in the online supporting information. Most textbooks at least mention 14 or 15 of these reactions, though many present aryl ketone reduction and the two nucleophilic aromatic substitution reactions in chapters other than the chapter(s) on aromatic chemistry. The exceptions are Brown et al. (9) and Smith (14), which present 13 and 11 reactions, respectively. The most substantial difference among the texts with regard to reactions discussed is that Smith (14) does not include nucleophilic aromatic substitution. The most often omitted reactions are desulfonation and the Birch reduction. Several of the aromatic reactions are rarely, if ever, discussed with any mechanistic detail. These include: desulfonation, except Bruice (10) and Wade (16); oxidation of benzylic carbons, nitro group reduction, and Sandmeyer reactions, except Brown et al. (9), Hornback (12), and Vollhardt and Schore (17). Most authors have chosen to present at least partial mechanisms for 10-11 of the reactions, although Brown et al. (9) and Smith (14) present 8 and 7, respectively. Most textbooks present a similar number of complete mechanisms (5-7), although McMurry (13) is notable for its low number of complete mechanisms (3) and Wade (16) for its high number (9). Analysis revealed 20 commonly presented carbonyl reactions of aldehydes and ketones (see Figure 6, and Table S7 in the online supporting information), yet none of the texts examined present all 20 of these. Commonly omitted reactions include: base-catalyzed hemiacetal formation, acetal hydrolysis, imine hydrolysis, enamine hydrolysis, cyanohydrin decomposition, and Baeyer-Villiger oxidation. It is possible that some texts refer to these hydrolysis reactions within one or more problems, but only reactions referred to within the text were examined in this study. Most textbooks mention between 14 and 18 of the carbonyl reactions examined, but Smith (14) introduces 19 and Solomons and Fryhle (15) introduce only 11. Many of the texts present at least partial mechanisms for all but one or two of the reactions: Hornback (12), McMurry (13), Solomons and Fryhle (15), Wade (16), and Vollhardt and Schore (17). The most significant exceptions were Brown et al. (9) (tied for the fewest number of at least partial mechanisms) and Smith (14) (tied for the largest number of at least partial mechanisms, but this text also introduces the largest number of reactions). The number of complete mechanisms presented varies significantly among the textbooks, with McMurry (13) presenting only 4 and both Smith (14) and Wade (16) presenting 13. Analysis of all 35 reactions suggests several trends. First, several reactions are discussed relatively infrequently (desulfonation, Birch reduction, base-catalyzed hemiacetal formation, acetal hydrolysis, imine hydrolysis, enamine hydrolysis, cyanohydrin decomposition, Baeyer-Villiger oxidation). Second, several reactions are rarely, if ever, discussed with any degree of mechanistic detail (desulfonation, benzylic carbon oxidation, nitro group reduction, Sandmeyer reactions, hydrolysis of carbonyl derivatives). Most textbooks provide a similar level of mechanistic detail, although McMurry (13) clearly provides less detail than the others, and Smith (14) and Wade (16) provide more. 596


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Conclusions Examination of the subject sequencing in nine organic textbooks has shown that, although they are similar in many ways, differences persist. The most significant difference among these textbooks is whether the first type of reactivity discussed is addition reactions of alkenes as in Brown et al. (9), Bruice (10), and McMurry (12), or whether the first type of reactivity discussed is substitution-elimination reactions of alkyl halides as in Carey (11), Hornback (12), Smith (14), Solomons and Fryhle (15), Wade (16), and Vollhardt and Schore (17). Another source of variability is the order by which carbonyl compounds and their reactivity is introduced, although all the textbooks introduce this after the reactivity of aromatic compounds. Most textbooks contain ∼250-350 questions on aromatic chemistry and 150-250 covering reactions at the carbonyl carbon of aldehydes and ketones. The Smith (14) textbook contains 441 total aldehyde and ketone problems. All textbooks place a heavy emphasis on predict-the-product, providethe-reagent, and multistep synthesis questions, yet the texts by Carey (11), Hornback (12), and Wade (16) do so more than some of the others. The Bruice (10), Carey (11), and Wade (16) textbooks emphasize structural topics more than the others. The textbooks by Brown et al. (9) and Wade (16) also contain more mechanistic questions. The most significant differences among the textbooks may be the lack of: provide-the-reagent questions in the chapters on aromatics as in Wade (16); kinetics questions in the chapters on carbonyls as in Brown et al. (9), Hornback (12), McMurry (13), Solomons and Fryhle (15), and Wade (16); and equilibrium questions in the chapters on carbonyls as in Brown et al. (9), McMurry (13), and Solomons and Fryhle (15). The textbooks examined cover a similar set of 35 reactions in the chapters on aromatics, aldehydes, and ketones. Significant differences include Smith's (14) omission of nucleophilic aromatic substitution, the large number of complete mechanisms in the textbooks by Smith (14) and Wade (16), and the small number of complete mechanisms in McMurry's (13) textbook. Several reactions were omitted more frequently than others; readers are encouraged to examine Tables S6 and S7 in the online supporting information to determine whether specific reactions of interest are covered in a particular textbook. Literature Cited Holden, M. S. J. Chem. Educ. 2000, 77, 31. Crouch, R. D. J. Chem. Educ. 2006, 83, 706–707. Spector, T. I. J. Chem. Educ. 2006, 83, 1603. Anderson, H. J.; Bauer, L. J. Chem. Educ. 1999, 76, 1151–1153. Lutz, R. P.; Wamser, C. C. J. Chem. Educ. 2001, 78, 1350– 1354. 6. Wheeler, D. M. S.; Wheeler, M. M. J. Chem. Educ. 1982, 59, 863– 865. 7. Amazon.com results of searching for “organic chemistry” in the “Books” category. http://www.amazon.com/s/ref=nb_sb_noss?url=searchalias%3Dstripbooks&field-keywords=organicþchemistry&x=7&y= 19 (accessed Mar 2010). 8. BarnesandNoble.com results of searching for “organic chemistry” in the “Textbooks” category. http://productsearch.barnesandnoble. com/search/results.aspx?WRD=organicþchemistry (accessed Mar 2010).

1. 2. 3. 4. 5.


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In the Classroom

9. Brown, W. H.; Foote, C. S.; Iverson, B. L.; Anslyn, E. Organic Chemistry, 5th ed.; Brooks/Cole Cengage Learning: Belmont, CA, 2009. 10. Bruice, P. Y. Organic Chemistry, 5th ed.; Pearson Prentice Hall: Upper Saddle River, NJ, 2007. 11. Carey, F. A. Organic Chemistry, 7th ed.; McGraw Hill: New York, 2008. 12. Hornback, J. M. Organic Chemistry, 2nd ed.; Thomson Brooks/ Cole: Belmont, CA, 2006. 13. McMurry, J. Organic Chemistry, 7th ed.; Thomson Brooks/Cole: Belmont, CA, 2008. 14. Smith, J. G. Organic Chemistry, 2nd ed.; McGraw Hill: New York, 2008. 15. Solomons, T. W. G.; Fryhle, C. B. Organic Chemistry, 9th ed.; Wiley: Hoboken, NJ, 2008. 16. Wade, L. G. Organic Chemistry, 6th ed.; Pearson Prentice Hall: Upper Saddle River, NJ, 2006.


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17. Vollhardt, K. P. C.; Schore, N. E. Organic Chemistry: Structure and Function, 5th ed.; W. H. Freeman and Company: New York, 2007.

Supporting Information Available Definitions and data collected in this study in tabular format, including: data on when infrared spectroscopy, mass spectrometry, nuclear magnetic spectroscopy, UV-vis spectroscopy, Lewis structures, structure-reactivity relationships, and bond-arrow formalism are introduced in each book; total number of pages, actual page of introduction of each subject, total number of problems, and reactions covered in the chapters on aromatics, aldehydes, and ketones; and publication dates for past and future editions of each text, cost for hardcover and electronic editions, and type of electronic homework available. This material is available via the Internet at http://pubs.acs.org.


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