A process in which a hydrogen atom in an organic compound is replaced by an acyl group (R-CO, where R = an organic group). The reaction involves substitution by a nucleophile (electron donor) at the electrophilic carbonyl group (C=O) of a carboxylic acid derivative. The substitution usually proceeds by an addition-elimination sequence. Two common reagents,
Two interrelated classes of chemical compounds, the precise definitions of which have varied considerably with the development of chemistry. Some of these controversies are still unresolved. Acids initially were defined only by their common properties as substances which had a sour taste, dissolved many metals, and reacted with alkalies (or bases) to form salts. For