Electron-Driven Acid-Base Chemistry: Proton Transfer from Hydrogen Chloride to Ammonia

• Published in: Science (American Association for the Advancement of Science) Vol. 319; no. 5865; pp. 936 - 939
• Main Authors: Eustis, Soren N, Radisic, Dunja, Bowen, Kit H, Bachorz, Rafał A, Haranczyk, Maciej, Schenter, Gregory K, Gutowski, Maciej
• Format: Journal Article
• Language: English
• Published: Washington, DC American Association for the Advancement of Science 15.02.2008; The American Association for the Advancement of Science
• Subjects: Acids; Anions; Chemical bonds; Chemistry; Chlorides; Electrons; Energy; Exact sciences and technology; General and physical chemistry; Hydrogen; Molecules; Photoelectron spectroscopy; Photoelectrons; Potential energy; Protons; Solution properties; Solutions; Spectrum analysis; Theory; Hydrochloric acid; Ammonia; Acid base balance; Proton transfer; Photoelectron spectrometry; Complexes; Mechanism; Hydrogen bond
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.1151614

In contrast to widely familiar acid-base behavior in solution, single molecules of NH₃ and HCl do not react to form the ionic salt, NH⁺₄Cl⁻, in isolation. We applied anion photoelectron spectroscopy and ab initio theory to investigate the interaction of an excess electron with the hydrogen-bonded complex NH₃···HCl. Our results show that an excess electron induces this complex to form the ionic salt. We propose a mechanism that proceeds through a dipole-bound state to form the negative ion of ionic ammonium chloride, a species that can also be characterized as a deformed Rydberg radical, NH₄, polarized by a chloride anion, Cl⁻.