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Title: Direct detection of pyridine formation by the reaction of CH (CD) with pyrrole: a ring expansion reaction

The reaction of the ground state methylidyne radical CH (X2Pi) with pyrrole (C4H5N) has been studied in a slow flow tube reactor using Multiplexed Photoionization Mass Spectrometry coupled to quasi-continuous tunable VUV synchrotron radiation at room temperature (295 K) and 90 oC (363 K), at 4 Torr (533 Pa). Laser photolysis of bromoform (CHBr3) at 248 nm (KrF excimer laser) is used to produce CH radicals that are free to react with pyrrole molecules in the gaseous mixture. A signal at m/z = 79 (C5H5N) is identified as the product of the reaction and resolved from 79Br atoms, and the result is consistent with CH addition to pyrrole followed by Helimination. The Photoionization Efficiency curve unambiguously identifies m/z = 79 as pyridine. With deuterated methylidyne radicals (CD), the product mass peak is shifted by +1 mass unit, consistent with the formation of C5H4DN and identified as deuterated pyridine (dpyridine). Within detection limits, there is no evidence that the addition intermediate complex undergoes hydrogen scrambling. The results are consistent with a reaction mechanism that proceeds via the direct CH (CD) cycloaddition or insertion into the five-member pyrrole ring, giving rise to ring expansion, followed by H atom elimination from the nitrogenmore » atom in the intermediate to form the resonance stabilized pyridine (d-pyridine) molecule. Implications to interstellar chemistry and planetary atmospheres, in particular Titan, as well as in gas-phase combustion processes, are discussed.« less
Authors:
; ; ; ; ; ;
Publication Date:
OSTI Identifier:
983158
Report Number(s):
LBNL-3290E
Journal ID: ISSN 1463-9076; ISSN 1463-9084; TRN: US1004565
DOE Contract Number:
DE-AC02-05CH11231
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Chemistry Chemical Physics
Research Org:
Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, CA (US)
Sponsoring Org:
Chemical Sciences Division
Country of Publication:
United States
Language:
English
Subject:
99 GENERAL AND MISCELLANEOUS; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; ATOMS; BROMOFORM; CHEMISTRY; COMBUSTION; DETECTION; EFFICIENCY; EXCIMER LASERS; GROUND STATES; HYDROGEN; LASERS; MASS SPECTROSCOPY; NITROGEN; PHOTOIONIZATION; PHOTOLYSIS; PLANETARY ATMOSPHERES; PYRIDINE; PYRROLES; RADICALS; REACTION KINETICS; RESONANCE; SYNCHROTRON RADIATION Direct detection, pyridine formation, pyrrole, ring expansion