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Aldehydes and to some extent even ketones, hydrate to geminal diols. The reaction is especially dominant for formaldehyde, which, in the presence of water, exists significantly as dihydroxymethane. Conceptually similar reactions include hydroamination and hydroalkoxylation, which involve adding amines and alcohols to alkenes.
Under acidic conditions, the hemiacetal and the alcohol can further react to form an acetal and water. Simple hemiacetals are usually unstable, although cyclic ones such as glucose can be stable. Acetals are stable, but revert to the aldehyde in the presence of acid. Aldehydes can react with water to form hydrates, R−CH(OH) 2.
Alcohol oxidation is a collection of oxidation reactions in organic chemistry that convert alcohols to aldehydes, ketones, carboxylic acids, and esters. The reaction mainly applies to primary and secondary alcohols. Secondary alcohols form ketones, while primary alcohols form aldehydes or carboxylic acids. [1] A variety of oxidants can be used.
Hydrazine, organohydrazines, and 1,1-diorganohydrazines react with aldehydes and ketones to give hydrazones. Phenylhydrazine reacts with reducing sugars to form hydrazones known as osazones, which was developed by German chemist Emil Fischer as a test to differentiate monosaccharides. [4] [5]
In an aldol condensation, water is subsequently eliminated and an α,β-unsaturated carbonyl is formed. The aldol cleavage or Retro-aldol reaction is the reverse reaction into the starting compounds. The name aldehyde-alcohol reaction derives from the reaction product in the case of a reaction among aldehydes, a β-hydroxy aldehyde.
Aldehydes and ketones can be reduced respectively to primary and secondary alcohols. In deoxygenation, the alcohol group can be further reduced and removed altogether by replacement with H. Two broad strategies exist for carbonyl reduction. One method, which is favored in industry, uses hydrogen as the reductant.
Hemiacetals form in the reaction between alcohols and aldehydes or ketones. Using an acid catalyst, the reaction proceeds via nucleophilic attack of the carbonyl group by the alcohol. [4] A subsequent nucleophilic attack of the hemiacetal by the alcohol results in an acetal. [2] Solutions of simple aldehydes in alcohols mainly consist of the ...
Reducing form of glucose (the aldehyde group is on the far right) A reducing sugar is any sugar that is capable of acting as a reducing agent. [1] In an alkaline solution, a reducing sugar forms some aldehyde or ketone, which allows it to act as a reducing agent, for example in Benedict's reagent. In such a reaction, the sugar becomes a ...