Kinetics of the Solvolyses of Benzhydryl Derivatives: Basis for the Construction of a Comprehensive Nucleofugality Scale

✍ Scribed by Bernard Denegri; André Streiter; Sandra Jurić; Armin R. Ofial; Olga Kronja; Herbert Mayr

• Publisher: John Wiley and Sons
• Year: 2006
• Tongue: English
• Weight: 148 KB
• Volume: 12
• Category: Article
• ISSN: 0947-6539
• DOI: 10.1002/chem.200500845

✦ Synopsis

Abstract

A series of 21 benzhydrylium ions (diarylmethylium ions) are proposed as reference electrofuges for the development of a general nucleofugality scale, where nucleofugality refers to a combination of leaving group and solvent. A total of 167 solvolysis rate constants of benzhydrylium tosylates, bromides, chlorides, trifluoroacetates, 3,5‐dinitrobenzoates, and 4‐nitrobenzoates, two‐thirds of which have been determined during this work, were subjected to a least‐squares fit according to the correlation equation log k~25 °C~ = s~f~(N~f~ + E~f~), where s~f~ and N~f~ are nucleofuge‐specific parameters and E~f~ is an electrofuge‐specific parameter. Although nucleofuges and electrofuges characterized in this way cover more than 12 orders of magnitude, a single set of the parameters, namely s~f~, N~f~, and E~f~, is sufficient to calculate the solvolysis rate constants at 25 °C with an accuracy of ±16 %. Because s~f~≈1 for all nucleofuges, that is, leaving group/solvent combinations, studied so far, qualitative discussions of nucleofugality can be based on N~f~.