Dimerization kinetics and products of. alpha. -substituted o-quinodimethanes derived from benzene and furan

Technical Report · Mon Jul 20 00:00:00 EDT 1992

DOI:https://doi.org/10.2172/7047444· OSTI ID:7047444

Leung, Man-kit

Effects of the {alpha}-substitutions on the termini of the reactive diene unit of o-quinodimethanes revealed a non-concerted mechanism for furan-based and benzene-based o-quinodimethane (o-QDM) dimerizations. In section one, the coexistence of the cisoid and transoid transition states in the diradical formation step is evidenced by the stereochemistry of the dimers. In view of the results of the furan-based o-QDM dimerizauons, it is believed that the regioselectivity in the diradical cyclization step is controlled mainly by the interaction between the active sites on the furan moieties in the diradical ring closure step, not by the intemal bond rotations of the carbon chain of the diradical intermediate. In section two, it was found that the trend of the regioselectivity. along the size of the {alpha}-substituents, of benzene-based o-QDM dimerizations is opposite to that of the Diels-Alder reactions. On the basis of the trends, it is suggested that the Diels-Alder reaction mechanism of benzene-based o-QDM's is concerted while the dimerization mechanism of benzene-based o-QDM's is stepwise. Because of their similar activation parameters, it is proposed that the parent o-xylylene and other o-xylylenes dimerize via a similar two step, diradical mechanism.

• Research Organization: Ames Lab., IA (United States)
• Sponsoring Organization: DOE; USDOE, Washington, DC (United States)
• DOE Contract Number: W-7405-ENG-82
• OSTI ID: 7047444
• Report Number(s): IS-T-1567; ON: DE92018813
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ADDUCTS
AROMATICS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CONDENSED AROMATICS
DIELS-ALDER REACTION
DIENES
DIMERIZATION
DIMERS
HYDROCARBONS
ISOMERS
KINETICS
MAGNETIC RESONANCE
NUCLEAR MAGNETIC RESONANCE
ORGANIC COMPOUNDS
POLYENES
POLYMERIZATION
REACTION INTERMEDIATES
REACTION KINETICS
RESONANCE
STEREOCHEMISTRY