The title compound was prepared by a reaction of 4-bromobenzoic acid with isopropylmagnesium chloride, formation of a (benzoate-O)(bromo)magnesium intermediate, further reaction with acetaldehyde, formation of 4-(1-hydroxyethyl)benzoic acid and a subsequent dehydration and elimination step.The synthesis of the target compound was achieved in 47.0% overall yield (99.4% pure) and the product thus obtained [i.e., 4-(vinyl)benzoic acid , 4-(ethenyl)benzoic acid] was confirmed by 1H-NMR, etc.