Kinetics of Reactions of CCN Radical with Alcohols

Abstract

The reaction kinetics of cyanomethylidyne radical, CCN(X2), with a series of primary alcohols were studied at about 1.33 kPa total pressure and room temperature using pulsed laser photolysis/laser-induced fluorescence (LP/LIF) technique. The CCN radical was produced via laser photolysis of CCl3CN with the fourth harmonic output of a Nd: YAG laser (266 nm). The relative concentration of the CCN(X2) radical was monitored by LIF in the (0, 0) band of the CCN(A2 X2) transition at 470.9 nm. Under pseudo-first-order conditions, the reaction rate constants of CCN(X2) with a series of primary alcohol molecules (n-CnH2n+1OH, n=1-6) were determined by measuring the time evolution of the relative concentration of CCN(X2i). The measured rate constants increased monotonously with the number of carbon atoms in the alcohols, and the values for reactions of CCN(X2) with alcohols were larger than those for reactions of CCN(X2) with alkanes (C1-C5). Based on the bond dissociation energies and linear free energy correlations, it was believed that the reactions of CCN(X2) with alcohols proceeded via a hydrogen abstraction mechanism that was analogous to CCN(X2) with alkanes. The experimental results indicated that the H atoms on the C-H bonds were activated at the presence of the OH group in alcohol molecules and the hydrogen abstraction from the C-H bonds in the alcohol molecules was the dominant reaction pathway. The relation between the rate constants and the long-distance attractive potentials between the CCN radical and the alcohol molecules was discussed.