A process for the preparation of compounds of the formula I ##STR1## where R is alkyl, by sulfonation, chlorination and nitration starting from an alkylbenzene, wherein the alkylbenzene is sulfonated with from 2.5 to 3, preferably from 2.65 to 2.75, moles of concentrated sulfuric acid per mole of alkylbenzene, the reaction product is then reacted with from about 1.1 to 1.3 moles of chlorine in the absence of a catalyst, the product is subsequently nitrated with highly concentrated nitric acid at elevated temperatures and the nitro compound is isolated.