Chapter 16 Aldehydes and Ketones I. Nucleophilic additions to the carbonyl group 16.1 Introduction Except for formaldehyde, the simplest aldehyde, all aldehydes have a carbonyl group, C=O, bonded on one side to a carbon, and on the other side to a hydrogen. In ketones, the carbonyl group is situated between two carbon atoms.
16.2 Nomenclature of aldehydes and ketones In the IUPAC system aliphatic aldehydes are named substitutively by replacing the final e of the name of the corresponding alkane with al For example
Aldehydes in which the –CHO group is attached to a ring system are named substitutively by adding the suffix carbaldehyde.
Aliphatic ketones are named substitutively by replacing the final e of the name of the corresponding alkane with one
Some aromatic aldehydes obtained from natural sources have very pleasant fragrances.
16.4 Synthesis of aldehydes 1. Oxidation
2 Reduction
16.5 Synthesis of ketones 1. Ketones (and aldehydes) by Ozonolysis of alkenes
2. Ketones from Friedel-Crafts Acylations
3. Ketones from Oxidations of secondary alcohols
4. Ketones from Alkynes
5. Ketones from Lithium Dialkylcuprates ( 二烷基酮锂）
6. Ketones from the reaction of nitriles with RMgX or RLi
16.6 Nucleophilic addition to the carbon-oxygen double bond
16.7 The addition of water and alcohols: Hydrates( 水合物 ), Acetals （缩醛）, and ketals( 缩酮 )
16.7B Hemiacetals and Hemiketals （半缩醛和半缩酮）
16.7C Acetals and cyclic ketals （缩醛和环状缩酮）
16.7D Acetals and cyclic ketals as protecting groups
Synthetic application
16.7E Thioacetals and thioketals; 硫缩醛和硫缩酮 Aldehydes and ketones react with thiols to form thioacetals and thioketals.
16.8 The addition of derivatives of ammonia Aldehydes and ketones react with a number of derivatives of ammonia in the general way shown in the following sequence:
16.8A 2,4-Dinitrophenylhydrazones, Semicarbazones, and oximes
Specific Examples 因为产物都是固体，利用此反应可以鉴定未知有机物。
16.8B Imines Aldehydes and ketones react with primary amines to form imines.
16.8C Hydrazones: The Wolff- Kishner reduction Hydrazones are the basis for a useful method to reduce carbonyl groups (C=O) of aldehydes and ketones to – CH 2 – groups, called the Wolff- Kishner reduction
16.9 The addition of hydrogen cyanide (HCN) and of sodium bisulfite (NaHSO 3 )
Cyanohydrins are useful intermediates in organic synthesis.
16.10 The addition of ylides( 叶立 德） : The wittig （魏悌希） reaction This reaction, known as the wittig reaction ， has proved to be a valuable method for synthesizing alkenes. Discovered in 1954 by Geroge Wittig, then at the University of Tubingen. Wittig was a co-winner of the Nobel prize for chemistry in 1979.
How to make phosphorus ylide?
16.11 The addition of organometallic reagents: The reformatsky reaction
The addition of an organo zinc reagent to the carbonyl group of an aldehyde or ketone is called the Reformatsky reaction
Examples of the Reformatsky reaction are the following:
16.12 Oxidation of aldehydes and ketones
16.12A The Baeyer-Villiger oxidation of aldehydes and ketones Both aldehydes and ketones are oxidized by peroxy acids. This reaction, called the Baeyer-Villiger oxidation.
The mechanism proposed for this reaction involves the following steps:
16.13 Chemical and spectroscopic analysis for aldehydes and ketones 16.13A Tollens’test( 托伦测试） (silver mirror test 银镜测试） Tollen’s test can distinguish with aldehydes and ketones
16.13B Spectroscopic properties of aldehydes and ketones
Additional problems---Homework 16.24, 16.26, 16.28, 16.31, 16.32, 16.42