Direct observation of O-xylylene (o-quinodimethane) in solution. Dimerization kinetics of some o-quinodimethanes. II. Kinetic and product studies on the dimerization of. cap alpha. -methyl-substituted of o-quinodimethanes. III. Direct observation of 1,2-napthoquinodimethane and 9,10-phenanthroquinodimethane. Dimerization kinetics of resonance-stabilized o-quinodimethanes

Thesis/Dissertation · Thu Jan 01 04:00:00 EST 1987

OSTI ID:5638167

Macias, J R

Fluoride ion induced 1,4-elimination from (o((trimethylsilyl)methyl)benzyl)trimethylammonium iodide (7) has been used to generate o-xylylene (1) in solution. o-Xylylene (1) was observed directly in solution by UV-visible spectroscopy. Using stopped-flow UV-visible spectroscopy it was determined that the dimerization of 1 follows second-order kinetics. Two ring-alkylated derivatives of 1, 4-t-butyl-1,2-xylylene (28) and 3,4-(1,1,3,3-tetramethyltrimethylene)-1,2-xylylene (29) were generated and observed by UV-visible spectroscopy. The rate constant for the dimerization of 28 of 29 was determined, and the similar rate constants observed for the dimerization of 1, 28, and 29 led to the conclusion that when undergoing dimerization the o-quinodimethane monomers prefer a non-endo approach. The dimerization kinetics of 5-ethylidene-6-methylene-1,3-cyclohexadiene (9) and 5,6-bis(ethylidene)-1,3-cyclohexadiene (10) were studied by stopped-flow UV-visible spectroscopy. The dimerization of 9 and 10 led predominantly to one stereoisomer in each case. The similar rate constants for the dimerization of o-xylylene (1) and 9, and the much slower rate constant observed for the dimerization of 10 provided evidence for a stepwise mechanism for the dimerization of benzenoid o-quinomethanes. The fluoride ion induced 1,4-elimination methodology used in the generation of o-xylylene (1) was utilized in the formation and observation of 1,2-napthoquinodimethane (2) and 9,10-phenanthroquinodimethane (3). o-Quinodimethane (2) was observed in solution by UV-visible spectroscopy while 3 was observed by /sup 1/H NMR spectroscopy. Both of these species were considerably more stable than 1. Both 2 and 3 dimerized following second-order kinetics.

• Research Organization: Iowa State Univ. of Science and Technology, Ames (USA)
• DOE Contract Number: W-7405-ENG-82
• OSTI ID: 5638167
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ALKANES
ANIONS
AROMATICS
AZAARENES
AZINES
CHARGED PARTICLES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
DIMERIZATION
FLUORINE COMPOUNDS
HALOGEN COMPOUNDS
HETEROCYCLIC COMPOUNDS
HYDROCARBONS
IONS
KINETICS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
POLYMERIZATION
PYRIDINES
QUINOLINES
REACTION KINETICS