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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.
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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
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Aldehydes in which the –CHO group is attached to a ring system are named substitutively by adding the suffix carbaldehyde.
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Aliphatic ketones are named substitutively by replacing the final e of the name of the corresponding alkane with one
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Some aromatic aldehydes obtained from natural sources have very pleasant fragrances.
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16.4 Synthesis of aldehydes 1. Oxidation
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2 Reduction
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16.5 Synthesis of ketones 1. Ketones (and aldehydes) by Ozonolysis of alkenes
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2. Ketones from Friedel-Crafts Acylations
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3. Ketones from Oxidations of secondary alcohols
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4. Ketones from Alkynes
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5. Ketones from Lithium Dialkylcuprates ( 二烷基酮锂)
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6. Ketones from the reaction of nitriles with RMgX or RLi
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16.6 Nucleophilic addition to the carbon-oxygen double bond
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16.7 The addition of water and alcohols: Hydrates( 水合物 ), Acetals (缩醛), and ketals( 缩酮 )
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16.7B Hemiacetals and Hemiketals (半缩醛和半缩酮)
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16.7C Acetals and cyclic ketals (缩醛和环状缩酮)
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16.7D Acetals and cyclic ketals as protecting groups
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Synthetic application
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16.7E Thioacetals and thioketals; 硫缩醛和硫缩酮 Aldehydes and ketones react with thiols to form thioacetals and thioketals.
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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:
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16.8A 2,4-Dinitrophenylhydrazones, Semicarbazones, and oximes
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Specific Examples 因为产物都是固体,利用此反应可以鉴定未知有机物。
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16.8B Imines Aldehydes and ketones react with primary amines to form imines.
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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
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16.9 The addition of hydrogen cyanide (HCN) and of sodium bisulfite (NaHSO 3 )
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Cyanohydrins are useful intermediates in organic synthesis.
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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.
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How to make phosphorus ylide?
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16.11 The addition of organometallic reagents: The reformatsky reaction
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The addition of an organo zinc reagent to the carbonyl group of an aldehyde or ketone is called the Reformatsky reaction
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Examples of the Reformatsky reaction are the following:
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16.12 Oxidation of aldehydes and ketones
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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.
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The mechanism proposed for this reaction involves the following steps:
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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
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16.13B Spectroscopic properties of aldehydes and ketones
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Additional problems---Homework 16.24, 16.26, 16.28, 16.31, 16.32, 16.42
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