110b Exam 2 Review Sheet- Spring Semester 2010 Review Session: Wednesday, February 24, 7:00 PM, SN Aud Examination: Friday, February 26, 8:00 AM, SN Aud 9 Goals for Chapter 16: 1. Nomenclature- be familiar with examples in the text. 2. Synthesis of aldehydes: PCC oxidation of 1° alcohols, know the reagent composition and reaction (review the mechanism). DIBAL reduction of esters; know the structure of the reagent and mechanism of reaction. Extend your mechanistic insights to the DIBAL reduction of nitriles. Li(Ot-Bu)3AlH reduction of acid chlorides to aldehydes: mechanism and utility in synthesis. 3. Synthesis of ketones: Review those from last semester and chapter 15. Ketones from the reaction of nitriles with RMgX or RLi, know the mechanism of this reaction and identify the unstable imine intermediate. 4. Acetals and ketals and their hemi- forms. Be able to identify these functional groups. Know the mechanism of formation/hydrolysis for an acetal (e.g., acetaldehyde + 2CH3OH + H+(cat.)). Be aware of the utility of acetals and ketals [and their thio (sulfur) analogs] as protecting groups in organic synthesis. 5. The addition of amines to aldehydes and ketones: mechanisms for imine and enamine formation. Applications of this chemistry. You should be familiar with the related chemistry of oximes and hydrazones. 6. The addition of HCN to aldehydes and ketones. Mechanism of cyanohydrin formation and synthetic utility of products. 7. The Wittig reaction. Mechanism of reaction, definition of ylide, betaine, oxaphosphatane. The Horner-Wadsworth-Emmons Modification. Utility in synthesis. 8. Spectroscopic evidence for aldehydes and ketones. 1H, 13C NMR and IR. 9. Be able to employ the reactions of chapter 16 in synthetic proposals, predict the products, and mechanistic analyses. 9 Goals for Chapter 17: 1. Acidity of the -hydrogen of carbonyl compounds; know the pKa’s of acetone, nitromethane, and acetonitrile. Why are these hydrogens acidic? What does an enolate ion look like? 2. Keto-enol tautomerism; rationalize the preferred keto form on the basis of select bond strengths. 3. Why do certain optically active aldehydes and ketones racemize easily? 4. Know the mechanisms of base-promoted -halogenation of aldehydes and ketones and the haloform reaction. What is the synthetic utility of these reactions? 5. The aldol reaction. Know the mechanism of the general reaction, focusing on three issues: (i) the “forward” direction, completely reversible, to yield a -hydroxy ketone or aldehyde, (ii) the “reverse” direction, or retro-aldol (usually from -hydroxy ketones), and (iii) irreversible dehydration of aldol addition products to yield conjugated systems (this happens at higher temperatures as well as for products whose elimination of H2O results in conjugated systems). Intramolecular aldol reaction gives a ring as a product. Acid-catalyzed variant of the aldol reaction: mechanism of reaction. 6. Extend your mechanistic insights to examples of crossed aldols, RCHO + X, where X = aldehydes, ketones (the Claisen-Schmidt reaction), nitroalkanes (products elaborated to amines via H2/Ni), and nitriles. R of course, is an aldehyde lacking an acidic -hydrogen. (We saw three examples). 7. Lithium enolates. Thermodynamic and kinetic enolates. Directed aldol reactions: mechanism of reaction. Alkylation of lithium enolates. 8. Definition of 1,2 vs. 1,4 addition to , unsaturated systems; mechanism of 1,4 attack; conjugate addition; Michael addition; mechanism of the Robinson annulation. 9. Be able to employ the reactions of chapter 17 in synthetic proposals, in “predict the product” type of questions, and mechanistic analyses.