| Popis: |
Production of α,α-dichloroaldehydes by direct chlorination of 1-alkanols with chlorine gas, catalyzed by DMF and DMF. HCl, was extended to long chain compounds (CnH2n+1OH; n = 5,6,8,10,12,14,16,18). Two problems specific to the longer chains were solved to obtain isolated yields in the range 70-85%; a) parasitic radical chlorination was largely controlled by shielding from light; b) alkyl alkanoate side product (8% for n=8 but ˜ 25% for n=16 or 18) was decreased to 0-2% in the presence of MgCl2.H2O. Homogeneity of the reaction medium was improved with chloroform as a cosolvent. Oxidation of the aldehydes to dichlorocarboxylic acids proceeded smoothly with aqueous KMnO4 up to the tetradecanal. For the longer chains 30% hydrogen peroxide-NaHCO3 in acetone (overnight at 48-52°C) was the preferred oxidant. |
