New temperature effect on tunnelling reaction in hydrogen, alkane, and ethanol in the solid phase

Rate constants for the tunneling reaction (HD + D → H + D2) in solid HD increase steeply with increasing temperature above 5 K, while they are almost constant below 4.2 K. The apparent activation energy for the tunneling reaction above 5 K is 95 K, which is consistent with the energy (91-112 K) for vacancy formation in solid hydrogen. The results above 5 K were explained by the model that the tunneling reaction was accelerated by a local motion of hydrogen molecules and hydrogen atoms. The model of the tunneling reaction assisted by the local motion of the reactants and products was applied to the temperature dependence of the proton-transfer tunneling reaction (C6 H6- + C2 H5 OH → C6 H7 + C2 H5 O-) in solid ethanol, the tunneling elimination of H2 molecule (CH3)2 CHCH(CH3)2+ → (CH3)2 C = C(CH3)2+ + H2) in solid 2,3-dimethylbutane, and the selective tunneling reaction of H atoms in solid neo-C5 H12 -alkane mixtures. (Author)