Ab initio Study on the Tautomerisms of Monosubstituted Tetrazoles

Ab initio method with MP2/6_31G and MP2/6_311G have been applied to study the isomeric reactions of monosubstituted tetrazoles.The results obtained show that:(1)the chain isomers[B]are more stable than the cyclic isomers[A],the energy differences between[A] and [B]are Δ E (= E [B] - E [A] =-225.834 76/MP2/6_31G(-219.530 42/MP2/6_311G)( R =H),-209.319 59/MP2/6-31G (-203.216 89/MP2/6_311G)( R =CH 3) and -235.009 03/MP2/6_31G(-234.165 98/MP2/6_311G)( R =CHO)kJ·mol -1 ,respectively;(2)the activation energies E a(= E TS - E [A] )of these isomeric reactions are 18.485 60/MP2/6_31G(27.265 00/MP2/6_311G)( R =H),10.817 31/MP2/6_31G(21.996 41/MP2/6-311G)( R =CH 3) and 27.759 38/MP2/6_31G(38.239 58/MP2/6_311G)( R =CHO)kJ·mol -1 ,respectively.