Electrostatic potential at atomic sites as a reactivity descriptor for hydrogen bonding. Complexes of monosubstituted acetylenes and ammonia

The applicability of molecular electrostatic potential values at atomic sites as a reactivity descriptor for the process of hydrogen bonding is assessed for a series of complexes involving acetylene and diacetylene derivatives as proton donors and ammonia as a model proton acceptor. The acetylenic compounds studied were of the type R-CdropC-H, Where R represents H, F, Cl, CH3, CH2F, CHF2, CF3, CH2Cl, CHCl2, CCl3, CN, H-CdropC, F-CdropC, Cl-CdropC. Density functional theory computations at the B3LYP/6-31G(d,p) level were employed. An excellent linear relation between the molecular electrostatic potential at the acetylenic hydrogen atom in the isolated acetylenes with the energy of hydrogen-bond formation is found. It is concluded that the value of the electrostatic potential at the acidic hydrogen atomic site can be used as a reactivity descriptor for the hydrogen bonding ability of the molecules studied.