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ALDEHYDES AND KETONES
This chapter discusses carbonyl compounds, including aldehydes and ketones. It covers nomenclature, reactivity, and reactions of carbonyl compounds. Specifically, it describes how aldehydes are more reactive than ketones due to increased partial positive charge and steric accessibility. It also summarizes key reactions such as addition, reduction, substitution involving nucleophiles, protecting groups, and stereochemistry of additions.
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ALDEHYDES AND KETONES
- 1. Organic Chemistry 4th Edition QBA Miguel A. Castro Ramírez Chapter 18 Carbonyl Compounds II Radicals Irene Lee Case Western Reserve University Cleveland, OH
- 2.
- 3. If the aldehydegroup is attached to a ring,
- 4. If a compoundhas two functional groups, the one with the lowest priority is indicated by its prefix
- 5.
- 7. If a ketonehas a second functional group of higher priority,
- 8. An aldehyde hasa greater partial positive charge on its carbonyl carbon than does a ketone
- 9. • Steric factorscontribute to the reactivity of an aldehyde • The carbonyl carbon of an aldehyde is more accessible to the nucleophile • Ketones have greater steric crowding in their transition states, so they have less stable transition states
- 10. Aldehydes and ketonesreact with nucleophiles to form addition products: nucleophile addition reactions
- 12. If the nucleophilethat adds to the aldehyde or ketone is an O or an N, a nucleophilic addition–elimination reaction will occur
- 13. Formation of aNew Carbon–Carbon Bond Using Grignard Reagents Grignard reagents react with aldehydes, ketones, and carboxylic acid derivatives
- 16.
- 17.
- 20. Utilization of DIBALto Control the Reduction Reaction
- 21. The reduction ofa carboxylic acid with LiAlH4 forms a single primary alcohol Acyl chloride is also reduced by LiAlH4 to yield an alcohol
- 22. An amide isreduced by LiAlH4 to an amine
- 23. Aldehydes and ketonesreact with a primary amine to form an imine This is a nucleophilic addition–elimination reaction The pH of the reaction must be controlled
- 24. Dependence of therate of the reaction of acetone with hydroxylamine on the pH of the reaction: a pH rate profile
- 25. Aldehydes and ketonesreact with secondary amines to form enamines
- 26. Formation of ImineDerivatives
- 27. Deoxygenation of theCarbonyl Group
- 28. Water adds toan aldehyde or ketone to form a hydrate
- 30. Why is theresuch a difference in the Keq values?
- 31. The equilibrium constantfor the reaction depends on the relative stabilities of the reactants and products
- 32. Addition of anAlcohol to an Aldehyde or a Ketone
- 33. Utilization of ProtectingGroups in Synthesis LiAlH4 will reduce the ester to yield an alcohol, but the keto group will also be reduced
- 34. The keto groupis protected as a ketal in this synthesis
- 35. The more reactivealdehyde is protected with the diol before reaction with the Grignard reagent
- 36. • The OHgroup in an alcohol can be protected as a trimethylsilyl ether • The OH group in a carboxylic acid can be protected as an ester • An amino group can be protected with an acetyl group
- 37. Addition of SulfurNucleophiles
- 38. Desulfurization replaces theC–S bonds with C–H bonds
- 39. Formation of Alkenes The Wittig Reaction
- 41. Preparation of thePhosphonium Ylide If two sets of reagents are available for the synthesis of an alkene, it is better to use the one that requires the less sterically hindered alkyl halides
- 42. • The Wittigreaction is completely regioselective • This reaction is the best way to make a terminal alkene • Stable ylides form primarily E isomers, and unstabilized ylides form primarily Z isomers • Stable ylides have a group (C=O) that can share the carbanion’s negative charge
- 43. Stereochemistry of Nucleophilic Addition Reaction
- 51. • Nucleophiles thatform unstable addition products form conjugated addition products, because the conjugate addition is not reversible • Nucleophiles that form stable addition products can form direct addition products or conjugate addition products • If the rate of direct addition is slowed down by steric hindrance, a Grignard reagent will form the conjugate addition product
- 52. Nucleophilic Addition toα,β-Unsaturated Carboxylic Acid Derivatives
- 53. Enzyme-Catalyzed Additions toα,β- Unsaturated Carbonyl Compounds