Effect of addition of phenols on the rate of Menschutkin reaction-Reaction , between phenacyl bromide and triethylamine

Abstract

Second order rate constants for the reaction between phenacyl bromide and triethylamine with and without phenols have been determined in aprotic solvents at 25°, 30° and 35°C. The addition of <i>X </i>- C₆H₄ - OH (<i>X= </i>H, <i>p-</i>OCH₃, <i>p-</i>CH₃, <i>p</i>-CI, <i>p-</i>Br and <i>p-</i>NO₂) with <i>pK_a </i> greater than 7.15 does not affeqt the rate of quaternization of triethylamine by phenacyl bromide, whereas strong acidic phenols such as 2,4-dinitrophenol and 2,4,6-trinitrophenol do affect the rate of quaternization. <i>pK_a </i> of phenol is found to be driving force for quaternization or protonation of triethylamine. The active nucleophiles in these processes are predicted.