The article is devoted to the study of the reaction of hydromentoxycarbonylation of isobutylene in the presence of palladium phosphine complexes in order to optimize the method of obtaining menthyl ether of isovaleric acid, which is the main component of the drug «Validol». The purpose of the article is to improve the methods of obtaining menthyl ether of isovaleric acid (the main active component of the drug "Validol") and to study the reaction of hudromentoxycarbonylation with l-menthol and carbon monoxide of isobutylene in the presence of homogeneous catalytic systems based on palladium phosphine complexes. The article presents studies on the content of validol from various types of raw materials by the method of GC analysis. In the commercial samples of validol obtained from natural l-menthol and industrial isovaleric acid (obtained as a result of the oxidation of "fermentation isoamyl alcohol"), there are 2 components (l-menthyl ether of l-menthol and isovaleric acid), additionally 2 % menthene hydrocarbon and 23 % L-menthyl ether of methyl ethylacetic acid. A probabilistic mechanism of the reaction of the hydromentoxycarbonylation of isobutylene with l-menthol and with carbon monoxide and in the presence of catalytic systems based on the studied palladium phosphine complexes is proposed.