Unimolecular thermal decomposition of dimethoxybenzenes.
J Chem Phys
; 140(23): 234302, 2014 Jun 21.
Article
em En
| MEDLINE
| ID: mdl-24952536
ABSTRACT
The unimolecular thermal decomposition mechanisms of o-, m-, and p-dimethoxybenzene (CH3O-C6H4-OCH3) have been studied using a high temperature, microtubular (µtubular) SiC reactor with a residence time of 100 µs. Product detection was carried out using single photon ionization (SPI, 10.487 eV) and resonance enhanced multiphoton ionization (REMPI) time-of-flight mass spectrometry and matrix infrared absorption spectroscopy from 400 K to 1600 K. The initial pyrolytic step for each isomer is methoxy bond homolysis to eliminate methyl radical. Subsequent thermolysis is unique for each isomer. In the case of o-CH3O-C6H4-OCH3, intramolecular H-transfer dominates leading to the formation of o-hydroxybenzaldehyde (o-HO-C6H4-CHO) and phenol (C6H5OH). Para-CH3O-C6H4-OCH3 immediately breaks the second methoxy bond to form p-benzoquinone, which decomposes further to cyclopentadienone (C5H4=O). Finally, the m-CH3O-C6H4-OCH3 isomer will predominantly follow a ring-reduction/CO-elimination mechanism to form C5H4=O. Electronic structure calculations and transition state theory are used to confirm mechanisms and comment on kinetics. Implications for lignin pyrolysis are discussed.
Texto completo:
1
Bases de dados:
MEDLINE
Assunto principal:
Benzaldeídos
/
Hidrogênio
Idioma:
En
Revista:
J Chem Phys
Ano de publicação:
2014
Tipo de documento:
Article
País de afiliação:
Estados Unidos