| 摘要 |
1,155,538. Production of #,#-dimethylacrylic acid. WACKER-CHEMIE G.m.b.H. 27 Oct., 1967 [28 Oct., 1966], No. 48951/67. Heading C2C. #,#-Dimethylacrylic acid is produced by reacting ketene with excess acetone in the presence of hexafluorophosphoric acid at between- 50‹ and 20‹ C. The reaction product is freed of excess acetone and converted into the #,#- dimethylacrylic acid by heating with the exclusion of water at 10-12 mm. Hg pressure at a temperature of between 100‹ and 140‹ C. A catalytic amount of a sparingly volatile inorganic acid or an alkali metal or alkaline earth metal hydroxide may be added before the heating stage. The product, or the sodium salt thereof, may be hydrogenated, e.g. with platinum dioxide or Raney nickel to yield isovaleric acid. Examples describe the use of a continuous process using an apparatus comprising a column and a reactor, both of which are capable of being cooled, and the subsequent hydrogenation of the product to isovaleric acid. |
