Comparison of the Hydride-Donating Ability and Activity of Five- and Six-Membered Benzoheterocyclic Compounds in Acetonitrile

In this work, we compared the hydride-donating ability of five-membered benzoheterocyclic compounds (FMB) and six-membered benzoheterocyclic compounds (SMB), isomers of DMBI and DMIZ and of DMPZ and DMPX, using detailed thermodynamic driving forces [Delta G(o) (XH)], kinetic intrinsic barriers (Delta G(XH/X)(not equal)), and thermo-kinetic parameters [Delta G(not equal)degrees (XH)]. For DMBI and DMIZ, the values of Delta G(o) (XH), Delta G(XH/X)(not equal), and Delta G(not equal)degrees (XH) are 49.2 and 53.7 kcal/mol, 35.88 and 42.04 kcal/mol, and 42.54 and 47.87 kcal/mol, respectively. For DMPZ and DMPX, the values of Delta G(o) (XH), Delta G(XH/X)(not equal), and Delta G(not equal)degrees (XH) are 73.2 and 79.5 kcal/mol, 35.34 and 25.02 kcal/mol, and 54.27 and 52.26 kcal/mol, respectively. It is easy to see that the FMB isomers are thermodynamically dominant and that the SMB isomers are kinetically dominant. Moreover, according to the analysis of Delta G(not equal)degrees (XH), compared to the SMB isomers, the FMB isomers have a stronger hydride-donating ability in actual chemical reactions.