Alcohols trichloroacetaldehyde

Oxidation and Reduction.—A number of selective oxidation procedures have been reported. Trichloroacetaldehyde on dehydrated chromatographic alumina converts the diol (15) into the 3/3-hydroxy-17-ketone (68%)." Primary alcohols are reported to be less readily oxidized than secondary alcohols by this reagent. Similarly, bromine or chlorine with HMPA oxidizes secondary alcohols more readily than primary alcohols. Thus the diol (16) was converted into the ketol (17)... 

A modification of the Oppenauer oxidation which uses trichloroacetaldehyde on alumina provides a good, general oxidation of alcohols, and in particular will oxidize a secondary akdiol in the presence of a primary one, as shown by the examples given in Scheme 16. This method is claimed to be superiw to silver carbonate on Celite and much cheaper. Other advantages of this method are that it is neutral, nonaqueous, and halide, ester and lactone functionalities survive the reaction conditions. ... 

The selective oxidation of secondary alcohols which contain either a sulfide or selenide is also possible using either selenium-based oxidizing agents (equations 39 and 40), or with a modified Oppe-nauer system involving trichloroacetaldehyde (equation 41). ... 

Chloral (trichloroacetaldehyde), CCI3CHO, oxidizes secondary alcohols to ketones in the presence of very active aluminum oxide (Woelm). This reaction seems to be superior to the Oppenauer oxidation, because it takes place at room temperature or at only slightly elevated temperatures [958, 959, 960],... 

Asymmetric anionic polymerization can convert trichloroacetaldehyde (chloral) to a one-handed helical, isotactic polymer (44) having a 4/1-helical conformation with high optical activity ([oi]d +4000° in film).28114-118 Anionic initiators such as 45,115 46,115 and 47117 and Li salts of optically active carboxylic acids or alcohols are used for the polymerization. Although the polymers are insoluble in solvents and their conformation in solution cannot be directly... 

Several new procedures for the selective oxidation of secondary alcohols in the presence of primary alcohols have appeared. Distannoxane-bromine, a neutral reagent, efficiently oxidizes secondary or benzylic alcohols to ketones in the presence of primary alochols.62 Trialkyltin alkoxides and bromine oxidize both primary and secondary alcohols.63 Woelm W-200, neutral, dehydrated alumina oxidizes secondary alcohols to ketones in the presence of primary alcohols with trichloroacetaldehyde as the hydride acceptor.6 The reverse reduction process had previously been reported. Oxidation of triphenylmethyl ethers of primary, secondary diols with triphenyl carbenium salts proceeds only at the secondary positions.65... 

Chlorinatioii of EAanoL Chloral Either 95 per cent or absolute ethyl alcohol can be chlorinated to produce trichloroacetaldehyde (chloral) through a series of reactions frequently represented as follows ... 

Chlorination of Ethanol. Ethyl alcohol either absolute or containing water is chlorinated to form the hemiacetal of trichloroacetaldehyde from which chloral is liberated by treatment with concentrated sulfuric acid. Ferric chloride may be employed as a chlorination catalyst, but its use does not appear necessary. Five moles of hydrogen chloride is liberated for each mole of chloral produced, and the other by-products include ethyl chloride, ethylene dichloride, and ethyl ether. 

Other addition reactions of aldehydes oeeur. Water, for example, adds to the earbonyl of trichloroacetaldehyde to form chloral hydrate, a strong hypnotic and sedative known as knock-out drops or (when mixed with alcohol) a Mickey Finn. Complete the reaction by drawing the structural formula of chloral hydrate ... 

With most other aldehydes or ketones, however, the hydrates cannot be isolated because they readily lose water to reform the carbonyl compound that is, the equilibrium constant (Sec. 3.11) is less than 1. An exception is trichloroacetaldehyde (chloral), which forms a stable crystalline hydrate, CCl3CH(OH)2. Chloral hydrate is used in medicine as a sedative and in veterinary medicine as a narcotic and anesthetic for horses, cattle, swine, and poultry. The potent drink known as a Mickey Finn is a combination of alcohol and chloral hydrate. 

Probably related mechanistically to the Oppenauer oxidations are several methods for oxidation that involve transfer of hydrogen to trichloroacetaldehyde. The reaction is mediated by alumina and is carried out by simply mixing the alcohol to be oxidized, the hydrogen acceptor, and alumina in an inert solvent. This reaction is suitable for selective oxidation of secondary alcohols in the presence of primary alcohols (which do not react) and also for the oxidation of compounds containing other easily oxidized functional groups. 

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