Peroxycarboxylic acids
When peroxycarboxylic acids - also known peracids - referred to representative of a group of materials of organic compounds containing a peroxycarboxylic (Peroxycarbonsäurengruppe) as the functional group contained. All peroxycarboxylic acids contain a free hydroperoxide group (HOO group) and can therefore be regarded as acyl hydroperoxides. Like most peroxides , the peroxycarboxylic acids are explosive in pure or highly concentrated form . The explosiveness decreases with increasing chain length. Short-chain aliphatic peroxycarboxylic acids are water-soluble up to ~ C 6 , after which the water-insoluble ( lipophilic ) part of the molecule predominates . Aromatic peroxycarboxylic acids are more soluble in organic solvents than in water.
Manufacturing
Peroxycarboxylic acids are prepared from carboxylic acids and hydrogen peroxide ( reverse reaction equation 2 under reactions ). Above all, aromatic peroxycarboxylic acids are prepared from carboxylic acid chlorides and hydrogen peroxide in a basic medium.
Peroxycarboxylic acids are also formed by the autoxidation of aldehydes .
Reactions
Peroxycarboxylic acids are usually unstable and are therefore only produced from the carboxylic acid and hydrogen peroxide during the reaction during syntheses ( in situ ). An exception is meta -chloroperbenzoic acid , which is crystalline and stable.
Peroxycarboxylic acids and alkenes can react to form epoxides at room temperature ( Prileschajew reaction ). In addition to the epoxide, a carboxylic acid is formed. Meta- chloroperbenzoic acid (MCPBA) is often used as the peroxycarboxylic acid . Other peroxycarboxylic acids that can be used for epoxidation are peroxyformic acid and peroxyacetic acid .
Peroxycarboxylic acids serve as oxidizing agents , for example in Baeyer-Villiger oxidations .
Peroxycarboxylic acids are weak acids and as such enter into acid-base reactions . Their salts can be used for purification and isolation.
literature
- Christian Caspari: The chemistry of organic peroxides with special consideration of safety aspects . April 26, 1998 ( PDF; 0.4 MB [accessed on March 21, 2007] thesis).
Individual evidence
- ↑ Otto-Albrecht Neumüller (Ed.): Römpps Chemie-Lexikon. Volume 4: M-Pk. 8th revised and expanded edition. Franckh'sche Verlagshandlung, Stuttgart 1985, ISBN 3-440-04514-5 , p. 3068.