Temperature Dependent Slow Reactions of C₂H₆⁺ with C₂H₆

Abstract

The reaction of C₂H₆⁺ with C₂H₆ was studied in a pulsed electron beam high ion source pressure mass spectrometer. Ethane at variable pressures in the 16—150 mTorr range in ~4 Torr hydrogen was used in experiments covering the temperature range from −145 to 400°C. Reaction: C₂H₆⁺+C₂H₆ was found to have a rate constant k=10^-6.6 T^-1.5 whose magnitude decreased with temperature. The reaction proceeds via a (C₄H₁₂⁺)^* intermediate, which at low temperature can be stabilized and becomes the major product. A very slow decrease of C₄H₁₂⁺ with time was observed at low temperature which was completely accounted for by an appearance and an increase of the trimer ion C₆H₁₈⁺. The two isomeric structures for C₄H₁₂⁺ are proposed in order to interpret the slow clustering reactions of C₄H₁₂⁺ with C₂H₆.