Thermal decomposition of propargyl bromide and the subsequent formation of benzene

Conference · Sat Dec 31 23:00:00 EST 1994 · Combustion and Flame; (United States)

OSTI ID:6535949

Kern, R D; Chen, H ^[1]; Kiefer, J H; Mudipalli, P S ^[2]

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1. University of New Orleans, LA (United States). Dept. of Chemistry
2. University of Illinois, Chicago (United States). Dept. of Chemical Engineering

Mixtures of 3% C[sub 3]H[sub 3]Br[sub 3], 3% CHBr = 5% H[sub 2], and 3% CHBr + 5% D[sub 2], all three containing neon diluent, were analyzed behind reflected shock waves by time-of-flight mass spectrometry to investigate the role of propargyl radical as precursor to benzene formation at high temperatures. The first mixture yields significant concentrations of benzene over the range 1,310--1,470 K; benzene yield is observed to increase twofold in the second mixture at comparable temperatures. The third mixture reveals a temporal ratio of HBr/(DBr + Br) [approximately] 1, which is interpreted as evidence of an equal contribution from each of the two initiation reactions: (1) CHBr [yields] c-C[sub 3]H[sub 2] + HBr, where c-C[sub 3]H[sub 2] is singlet cyclopropenylidene; and (2) CHBr [yields] C[sub 3]H[sub 3] + Br. In the first two mixtures, the major products are acetylene, butadiyne, C[sub 6]H[sub 2], benzene and HBr. A 2% propyne + neon mixture was also studied over the temperature range 1,750--2,620 K. The reaction profiles for propyne, acetylene, butadiyne, and benzene are modeled satisfactorily with a mechanism in which the dominant channel for propyne dissociation produces c-C[sub 3]H[sub 2] + H[sub 2]. Reaction pathways involving c-C[sub 3]H[sub 2] insertion into C-H bonds are presented along with an analysis for the important disproportionation step, c-C[sub 3]H[sub 2] + propyne [yields] 2C[sub 3]H[sub 3]. Inclusion of six steps describing the reactions of bromine containing species to the core propyne decomposition mechanism results in satisfactory fits to the CHBr and CHBr + H[sub 2] experiments. It is concluded that benzene production in these mixtures is best explained by a sequence of reactions initiated by the dimerization of propargyl radicals.

• OSTI ID: 6535949
• Report Number(s): CONF-940711--
• Journal Information: Combustion and Flame; (United States), Journal Name: Combustion and Flame; (United States) Vol. 100:1-2; ISSN CBFMAO; ISSN 0010-2180
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400800* -- Combustion
Pyrolysis
& High-Temperature Chemistry
AROMATICS
BENZENE
BINARY MIXTURES
BROMINATED ALIPHATIC HYDROCARBONS
CHEMICAL REACTION KINETICS
CHEMICAL REACTION YIELD
CHEMICAL REACTIONS
COMBUSTION KINETICS
DECOMPOSITION
DEUTERIUM
DIMERIZATION
DISPERSIONS
ELEMENTS
HALOGENATED ALIPHATIC HYDROCARBONS
HYDROCARBONS
HYDROGEN
HYDROGEN ISOTOPES
ISOTOPES
KINETICS
LIGHT NUCLEI
MIXTURES
NONMETALS
NUCLEI
ODD-ODD NUCLEI
ORGANIC BROMINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
POLYMERIZATION
PYROLYSIS
REACTION INTERMEDIATES
REACTION KINETICS
SOOT
STABLE ISOTOPES
THERMOCHEMICAL PROCESSES
YIELDS