Treatment of an alkene (A) with Hg(OAc)_2 \ in \ H_2O/ THF, followed by NaBH_4, produces an alcohol isomeric to one obtained by hydroboration-oxidation of the same alkene. Reduction of the alkene gives compound (B) 2-methylbutane, while ozonolysis yields an aldehyde, CH_3CHO, as one of the products. Find the structure of the alkene.