Additivity of substituent effects in the fluoroarene series: Equilibrium acidity in the gas phase and deprotonation rates in ethereal solution

✍ Scribed by H.H. Büker; N.M.M. Nibbering; D. Espinosa; F. Mongin; Manfred Schlosser

• Book ID: 104258342
• Publisher: Elsevier Science
• Year: 1997
• Tongue: French
• Weight: 229 KB
• Volume: 38
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(97)10303-3

✦ Synopsis

Benzene and all mono-, ddi-, tri-, tetra-and pentafluoro substituted defivativos thereof were equilibrated with the corresponding atyl anions in the gas phase. Perfect additivity of the substituent effects on the acidity was observe~ The basicifies were dimini~h~ by 12, 6 and 4 kcal/mol depending on whether the supplementary fluorine atom occupied the ortho, meta or para position with respect to the deprotonafion site. On the other hand, substituant effects on the rates of hydrogen/metal interconversion processes level off with incrm~ing numbers of halogens. For example, while the free energy of activation of sec-Soutyllithium promoted lithiation of fluorobenzane is at least 4 kcal/mol ~smmllfr than that of benzene, the difference was found to shrink to less than 2.5 kcal/mol when pentafluo~ne and 1,2,3,4-tetrafluombenzene were compared.