Aldehydes alcohol reaction with

Aldehydes and ketones undergo reversible addition reactions with alcohols. The product of addition of one mole of alcohol to an aldehyde or ketone is referred to as a hemiacetal or hemiketal, respectively. Dehydration followed by addition of a second molecule of alcohol gives an acetal or ketal. This second phase of the process can be catalyzed only by acids, since a necessary step is elimination of hydroxide (as water) from the tetrahedral intermediate. There is no low-energy mechanism for base assistance of this... 

Aldehydes and ketones undergo acid-catalyzed reaction with alcohols to yield heniiacetals, compounds that have one alcohol-like oxygen and one ether-like oxygen bonded to the same carbon. Further reaction of a hemiacetal with alcohol then yields an iicetal, a compound that has two ether-like oxygens bonded to the same carbon. 

We said in Section 19.10 that aldehydes and ketones undergo a rapid and reversible nucleophilic addition reaction with alcohols to form hemiacetals. 

Acrolein is a highly reactive compound because both the double bond and aldehydic moieties partidpate in a variety of reactions, including oxidation, reduction, reactions with alcohols yielding alkoxy propionaldehydes,... 

Reaction LXXXI. Action of Hydrogen Chloride on a Mixture of an Aldehyde and an Alcohol. (B., 30, 3053 31, 545.)—The reaction is of the same type as the preceding. Under the influence of condensing agents, calcium chloride, hydrogen chloride, etc., aldehydes combine with alcohols to yield the ethers of the hypothetical dihydroxy compounds from which the aldehydes are derived. Ketones form these compounds only with difficulty. 

We saw in the previous chapter that aldehydes react with alcohols to form hemi-acetals, and hemiacetals react with another alcohol to afford acetals. Well, the intramolecular reaction of the aldehyde carbon of an aldose monosaccharide with one of the hydroxyl groups in the same molecule affords a cyclic hemiac-etal. An mferaiolecular reaction of this hemiacetal with the hydroxyl group of another sugar molecule provides an acetal functional group. This kind of acetal linkage connects monosaccharides into polysaccharides. Biochemists refer to these acetal (and ketal) bonds as glycoside bonds. 

Sec. 19.10) from ketones and aldehydes by acid-catalyzed reaction with alcohols... 

All the foregoing syntheses of 0,0,0-orthoesters required at least two steps because 0,0,0-orthoesters cannot usually be prepared directly from esters by reaction with alcohols under add conditions analogous to the preparation of acetals from aldehydes and ketones. There are some exceptions.237 -239 For example. reaction of the racemic mixture of cis- and fraftf-lactones in Scheme 2.115 with (/ ,/ )-butane-2,3-diol in refluxing benzene afforded a mixture of four diastereoisomeric orthoesters (99%) in the ratio 6 6 1 1 that could be sepa-... 

The methods discussed so far are applicable to aldehydes, ketones, esters and lactones. Hie a-haloge-nation of acids has received relatively little attention, although the traditional Hell-Vollaid-Zelinski conditions are adequate in most instances (equation 2). Alternative conditions have been developed, however, in which the acyl halide may be halogenated using NBS. ( eiKhing the reaction with alcohols or amines offers the opportunity of forming carboxylate derivatives. 

The mechanism for the oxidation of 1° alcohols to aldehydes parallels the oxidation of 2° alcohols to ketones detailed in Section 12.12A. Oxidation of a 1 alcohol to a carboxylic acid requires three operations oxidation first to the aldehyde, reaction with water, and then further oxidation to the carboxylic acid, as shown in Mechanism 12.6. 

The tri-chlorine substitution product of methane is the common and very important anesthetic chloroform. It may be made by the method referred to, viz., by the direct chlorination of methane. This method is not, however, a practical one. The industrial preparation is from alcohol or acetone, by treatment with chlorine and an alkali. In the reaction with alcohol the chlorine acts, first, as an oxidizing agent, oxidizing the alcohol to aldehyde. The chlorine then acts as a substituting agent forming a tri-chlorine substitution product of the aldehyde. This tri-chlor aldehyde is then decomposed by the alkali and chloroform results. The steps in this reaction have been definitely proven, as follows ... 

This constitution of the hydrate is indicated by the fact that it does not give the aldehyde reaction with fuchsine as does both acet-aldehyde and chloral. Also by the fact that the ethyl ester of such a di-hydroxy alcohol is known and is formed from chloral by reaction with alcohol. 

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