H/D secondary isotope effects in the thermal decomposition of a 1,2-diaza-1-cyclobutene. Mechanism of thermolysis

Journal Article · Wed Dec 01 04:00:00 EST 1982 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00388a086· OSTI ID:6447492

Olsen, H

The ..gamma.. secondary deuterium isotope effects in the pyrolysis of 1,2-diaza-1-cyclobutene has been determined. Values of the rate constants for the reaction in five experiments are tabulated. The results indicated that the decomposition proceeded by a mechanism involving an unsymmetrical transition state with elementary kinetic effects for the first D exchange unequal to the second D exchange for the breaking of the individual C-N bonds. Values of (k/sub H//k/sub D/)/sub ..cap alpha../ and (k/sub H//k/sub D/)/sub ..beta../ obtained indicated changes in hybridization in the respective directions sp/sup 2.x/ ..-->.. sp/sup 2/ and sp/sup 2.x/ ..-->.. sp/sup 3/ in agreement with the assumption that the carbon atoms in the diazacyclobutene ring should be hybridized between sp/sup 2/ and sp/sup 3/. Since the C atom belonging to the breaking of the C-N bond should adopt tetrahedral geometry at the saddle point, the changes observed in the isotope effect are consistent with a diradical-like transition state. This is in agreement with recent theoretical studies of diazetine fragmentation. The results of this study only furnished information about how unequally the two C-N bonds rupture in the transition state. The nature of the pathway is left unanswered. (BLM)

• Research Organization: Swiss Federal Inst. of Tech., Zuerich
• OSTI ID: 6447492
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 104:24; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400302* -- Organic Chemistry-- Isotope Effects-- (-1987)
ALKENES
CHEMICAL REACTIONS
CYCLOALKENES
DATA
DECOMPOSITION
DEUTERIUM
ELECTRONIC STRUCTURE
EXPERIMENTAL DATA
HYBRIDIZATION
HYDROCARBONS
HYDROGEN ISOTOPES
INFORMATION
ISOTOPE EFFECTS
ISOTOPES
KINETICS
LIGHT NUCLEI
NUCLEI
NUMERICAL DATA
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PYROLYSIS
REACTION KINETICS
STABLE ISOTOPES
THERMOCHEMICAL PROCESSES