Product Branching in the Low Temperature Reaction of CN with Propyne by Chirped-Pulse Microwave Spectroscopy in a Uniform Supersonic Flow.
A new chirped-pulse/uniform flow (CPUF) spectrometer has been developed and used to determine product branching in a multichannel reaction. With this technique, bimolecular reactions can be initiated in a cold, thermalized, high-density molecular flow and a broadband microwave spectrum acquired for all products with rotational transitions within a chosen frequency window. In this work, the CN + CH3CCH reaction was found to yield HCN via a direct H-abstraction reaction, whereas indirect addition/elimination pathways to HCCCN, CH3CCCN, and CH2CCHCN were also probed. From these observations, quantitative branching ratios were established for all products as 12(5)%, 66(4)%, 22(6)%, and 0(8)% into HCN, HCCCN, CH3CCCN, and CH2CCHCN, respectively. The values are consistent with statistical calculations based on new ab initio results at the CBS-QB3 level of theory. This work is a demonstration of CPUF as a powerful technique for quantitatively determining the branching into polyatomic products from a bimolecular reaction.
†Department of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, Michigan 48202, United States.
Chamara
C
Abeysekera
†Department of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, Michigan 48202, United States.
Baptiste
B
Joalland
†Department of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, Michigan 48202, United States.
Nuwandi
N
Ariyasingha
†Department of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, Michigan 48202, United States.
Lindsay N
LN
Zack
‡Institut de Physique de Rennes, UMR CNRS-UR1 6251, Université de Rennes 1, 263 Avenue du Général Leclerc, 35042, Rennes CEDEX, France.
Ian R
IR
Sims
§Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
Robert W
RW
Field
†Department of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, Michigan 48202, United States.
Arthur G
AG
Suits
CRESU; Laval; Reaction dynamics; Titan; cyano radical; rotational spectroscopy