A process for preparing aldehydes, ketones, carboxylic acids and esters by reaction of various substrates with carbon tetrahalides in the presence of a strong base. The reactions are accelerated by the presence of a polar solvent. Anions of the substrate attack the carbon tetrahalide to produce a halogenated intermediate and a dihalocarbene. The halogenated intermediate reacts with the base to form the indicated products. By the reactions of this process, primary alcohols are converted to aldehydes, carboxylic acids and esters, secondary alcohols are converted to ketones and ketones having an .alpha.-methyl group or both .alpha. and .alpha.' hydrogens are converted to carboxylic acids and esters. Non .alpha.-methyl ketones having .alpha. but no .alpha.' hydrogens are simply .alpha.-halogenated. The dihalocarbene generated in the reaction may attack the product, solvent, or another substrate to form other products.