Electric field-driven acid-base transformation: proton transfer from acid(HBr/HF) to base(NH3/H2O)
Hailong Liang , Baojie Chai , Guanghui Chen , Wei Chen , Sheng Chen , Hailan Xiao , Shujuan Lin
Chemical Research in Chinese Universities ›› 2015, Vol. 31 ›› Issue (3) : 418 -426.
Electric field-driven acid-base transformation: proton transfer from acid(HBr/HF) to base(NH3/H2O)
The proton-transfer between ammonia/water and HF/HBr without and with the stimulus of external electric fields(E ext) was investigated with the ab initio calculations. When external electric field is applied, the proton transfer occurs, resulting in ion-paired H4N+X- and H3O+X-(X=Br and F) from hydrogen-bonded complexes in view of the great changes of geometrical structures, dipole moments, frontier molecular orbitals and potential energy surfaces in the critical external electric fields(E c) of 1.131×107 V/cm for H3N-HBr, 1.378×108 V/cm for H3N-HF, 9.358×107 V/cm for H2O-HBr and 2.304×108 V/cm for H2O-HF, respectively. Furthermore, one or three excess electrons can trigger the proton transfer from H3N-HBr and H3N-HF to H4N+Br- and H4N+F-, while two and four excess electrons can induce the proton transfer from H2O-HBr and H2O-HF to H3O+Br- and H3O+F-, respectively. Compared with that of the analogous NH3/H2O-HCl systems, the strength of E c of proton transfer increases from HBr to HCl and HF for either H3N-HX or H2O-HX series, which is understandable by the fact that the acidity sequence is HBr>HCl>HF. And the larger of acidity of conjugated acid, the smaller of needed E c. On the other hand, the E c for the systems of NH3 with a stronger basicity is generally smaller than that of H2O systems for the same conjugated acid.
Electric field / Proton transfer / H3N-HX and H2O-HX(X=Br and F) systems
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