Salicylic acid and related compounds

See Industrial hygiene Materials reliability Plant safety. 

Kirk-Othmer Encyclopedia of Chemical Technology (4th Edition) 

The hydroxyben2oic acids have both hydroxyl and the carboxyl groups and, therefore, participate in chemical reactions characteristic of each of these moieties. In addition, these acids can undergo electrophilic ring substitution. The following reactions are discussed in terms of saUcyhc acid, but are characteristic of all the hydroxyben2oic acids. 

Carboxylic Acid Group. Reactions of the carboxyl group include decarboxylation, reduction to alcohols, and the formation of salts, acyl hahdes, amides, and esters. 

Generally, the carboxyl group is not readily reduced. Lithium aluminum hydride is one of the few reagents that can reduce these organic acids to alcohols. The scheme involves the formation of an alkoxide, which is hydroly2ed to the alcohol. Commercially, the alternative to direct reduction involves esterification of the acid followed by the reduction of the ester. 

Related to salicylic acid as isomers are / -hydroxybenzoic acid [99-06-9] andy -hydroxybenzoic acid [99-96-7]. The three are commonly known as the monohydroxybenzoic acids because of the shared chemical reactions, the three isomers are discussed together herein. These monohydroxybenzoic acids have a broad range of applications from paper coatings and liquid crystal preparations to drugs. Salicylic acid and its derivatives are interesting because of their demonstrated activity as analgesics, antipyretics, and antiinflammatory agents, whereas the para-substituted acids and esters known as parabens have activity as preservatives for food. 

0-Hydroxybenzoic acid is obtained as white crystals, fine needles, or fluffy white crystalline powder. It is stable in air and may discolor gradually in sunlight. The synthetic form is white and odorless. When prepared from natural methyl salicylate, it may have a light yellow or pink tint and a faint, wintergreen-like odor. w-Hydroxybenzoic acid crystallizes from water in the form of white needles and from alcohol as platelets or rhombic prisms. -Hydroxybenzoic acid crystallizes in the form of monoclinic prisms. Various physical properties of hydroxybenzoic acids are listed in Tables 1—4. 

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SALICYLIC ACID AND RELATED COMPOUNDS] (Vol 21) l-Acetamido-2-pyrrolidinone [7491-74-9]... 

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