[3] Carboxylic Acids | B.Sc. 2nd Year | Miss chemistry

Описание: Carboxylic acids belong to a class of organic compounds in which a carbon (C) atom is bonded to an oxygen (O) atom by a double bond and to a hydroxyl group (−OH) by a single bond. A fourth bond links the carbon atom to a hydrocarbon group (R). The carboxyl (COOH) group is named after the carbonyl group (C=O) and hydroxyl group.

In general, carboxylic acids undergo a nucleophilic substitution reaction where the nucleophile (-OH) is substituted by another nucleophile (Nu). The carbonyl group (C=O) gets polarized (i.e. there is a charge separation), since oxygen is more electronegative than carbon and pulls the electron density towards itself. As a result, the carbon atom develops a partial positive charge (δ+) and the oxygen atom develops a partial negative charge (δ-). In some cases, in the vicinity of a strong electrophile, the partially negatively charged carbonyl oxygen (δ-) can act as a nucleophile and attack the electrophile (as you will notice in the example of acid chloride synthesis, discussed later in this tutorial).

Compounds in which the −OH group of the carboxylic acid is replaced by other functional groups are called carboxylic acid derivatives, the most important of which are acyl halides, acid anhydrides, esters, and amides.

Acid chloride (ROCl)

Acid chlorides are formed when carboxylic acids react with thionyl chloride (SOCl_{2}2​start subscript, 2, end subscript), PCl_{3}3​start subscript, 3, end subscript or PCl_{5}5​start subscript, 5, end subscript. They are the most reactive derivatives of carboxylic acid.

Ester (RCOOR’)

Esters are derived when a carboxylic acid reacts with an alcohol. Esters containing long alkyl chains (R) are main constituents of animal and vegetable fats and oils. Many esters containing small alkyl chains are fruity in smell, and are commonly used in fragrances.

Thioester (RCOSR’)

Thioesterification: A thioester is formed when a carboxylic acid reacts with a thiol (RSH) in the presence of an acid.

◆Carboxylic acids parts➡

Part 1
   • [1] Carboxylic Acids | B.Sc. 2nd Year | Mi...  
Part 2
   • [2] Carboxylic Acids | B.Sc. 2nd Year | Mi...  
part 3
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