Electric Field-driven Acid-base Transformation： Proton Transfer from Acid（HBr/HF） to Base（NH3/H2O）

• Published in: 高等学校化学研究：英文版 2015 (3), p.418-426
• Main Author: LIANG Hailong CHAI Baojie CHEN Guanghui CHEN Wei CHEN Sheng XIAO Hailan LIN Shujuan
• Format: Article
• Language: English
• Subjects: H2O; HBR; NH3; 电场驱动; 质子转移; 酸碱
• ISSN: 1005-9040; 2210-3171

The proton-transfer between ammonia/water and HF/HBr without and with the stimulus of external electric fields（Eext） was investigated with the ab initio calculations. When external electric field is applied, the proton transfer occurs, resulting in ion-paired HaN＋X- and H30＋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（Ec） 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 HaN＋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 H30＋F-, respectively. Compared with that of the analogous NH3/H2O-HC1 systems, the strength of Ec 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〉HCI〉HF. And the larger of acidity of conjugated acid, the smaller of needed Ec. On the other hand, the Ec for the systems of NH3 with a stronger basicity is generally smaller than that of H2O systems for the same con- jugated acid.