PURPOSE: To industrially, efficiently and inexpensively obtain 2,3-dimethyl-2- butene useful as a raw material for a perfume, an agrochemical, etc., by isomerizing 2,3-dimethyl-1-butene in the presence of a prescribed derivative in a vapor phase without causing danger in a reaction, environmental pollution, etc.

CONSTITUTION: This compound is obtained by isomerizing (B) 2,3-dimethyl-1- butene in the presence of (A) magnesium oxide as a catalyst. For example, the reaction is carried out by supplying 0.01-100 pts.wt., especially 0.1-20 pts.wt. of the component B based on 1 pt.wt. of the component A per unit time to a vapor-phase reactor containing the component A at 100-500°C, especially 150-300°C under atmospheric pressure.