Solid or semisolid paraffin hydrocarbons or mixtures consisting mainly thereof are halogenated and then subjected to condensation, either in the presence of a condensing agent or under the influence of silent electric discharge. Aromatic hydrocarbons, for example, C16H8, or liquid olefins or other liquid hydrocarbons may be added before condensation. Gaseous olefins may be led into the mixture during condensation. The starting materials or the condensation products may be hydrogenated. Gives examples and numerous details.