| Popis: |
Chloride ions formed during the chlorination of ketones with sulfuryl chloride catalyze the production of chlorine. The phenomenon can be suppressed by addition of chlorosulfonic acid, causing a significant change in the regioselectivity of chlorination of 2-alkanones. Thus from 4-methyl-2-pentanone in the presence of chlorosulfonic acid and the N,N-dime-thyloctylammonium salt the 3,3-dichloroketone was obtained with 76-78% selectivity (70% isolated) at 40 ± 7°C. After 24h at 90-105°C the 1,1,3,3-tetrachloroketone was formed with 90-92% selectivity and isolated in 80% yield after haloform cleavage of the 1,1,1,3-isomer. In the absence of chlorine the chlorination involves equilibrated mixtures of enolic intermediates due to competing C-protonation. |
