α,α‐Dichloroaldehydes and α,α‐Dichlorocarboxylic Acids from Long Chain 1‐Alkanols. Improved Chlorination in the System DMF‐CHCl3‐MgCl21

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 KMnO4up to the tetradecanal. For the longer chains 30% hydrogen peroxide‐NaHCO3in acetone (overnight at 48‐52°C) was the preferred oxidant.