| Lewis Acid |
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| CATEGORIES ABOUT LEWIS ACID | |
| acid-base chemistry | |
| acids | |
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An Electrophile or electron acceptor is a Lewis acid. A Lewis acid usually has a low-energy LUMO , which interacts with the HOMO of the Lewis base. Unlike a Brønsted-Lowry Acid , which always transfers a Hydrogen Ion (H+), a Lewis acid can be '''''any''''' electrophile (including H+). Although all Brønsted-Lowry acids are Lewis acids, in common usage the term ''Lewis acid'' is often reserved for those Lewis acids which are not Brønsted-Lowry acids. The reactivity of Lewis acids can be judged from the Hard-Soft Acid-Base Concept . There is no universally valid description of Lewis acid ''strength'', because Lewis acid strength depends on the specific Lewis base. Christe and Dixon have predicted Lewis acid strength based on a computational model of gas-phase affinity for Fluoride , and out of a selection of common isolable Lewis acids they found that SbF5 had the strongest fluoride affinity. Fluoride is a "hard" Lewis base; Chloride and "softer" Lewis bases are very difficult to study because of limitations of the computational methods, and Lewis acidity in Solution suffers from the same restriction. Some common Lewis acids include Aluminium Chloride , Iron(III) Chloride , Boron Trifluoride , Niobium Pentachloride and Ytterbium(III) Triflate . REFERENCES |
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