| 摘要 |
1,224,642. Dehydroacetic acid. UNION CARBIDE CORP. 15 May, 1968 [22 May, 1967], No. 22967/68. Heading C2C. Dehydroacetic acid is prepared by the dimerization of diketene in the presence of an imidazole of general formula where R 1 is C 1-20 alkyl, alkoxyalkyl, hydroxyalkyl, haloalkyl free of α-halogen, acyloxyalkyl, alkynyl, alkenyl or aralkyl, R 2 , R 3 and R 4 are hydrogen or a radical R 1 . The reaction is preferably carried out in a solvent at a temperature in the range 0‹ to 50‹ C. The amount of catalyst employed is generally 0À03 to 5À0% by weight with respect to imidazole. A solvent mixture comprising a C 3-10 ketone and a hydrocarbon normally liquid at room temperature is preferably employed. |
