NON-PLANAR STRUCTURES OF THE HIGH-ENERGY ROTATIONAL CONFORMERS OF \\ 2-METHYLBUTA-1,3-DIENE (ISOPRENE) AND 2,3-DIMETHYLBUTA-1,3-DIENE

% Yu.~N.~Panchenko, Ch.~W.~Bock, J.~D.~Larkin, A.~V.~Abramenkov, F.~Kuhnemann, \textit{Struct. Chem.% Yu.~N.~Panchenko, Ch.~W.~Bock, J.~D.~Larkin, A.~V.~Abramenkov, \textit{Struct. Chem.