Temperature-dependent geometric isomerization versus fragmentation of 1,2-dideuteriocyclobutane

Journal Article · Wed Nov 11 04:00:00 EST 1987 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00257a073· OSTI ID:7076492

Lewis, D K; Glenar, D A; Kalra, B L; Baldwin, J E; Cianciosi, S J

Fresh insights on the 1,4-diradical tetramethylene generated thermally from tetrahydropyridazine (TP) and from cyclobutane (CB) have been gained through studies of stereospecifically deuteriated substrates. At 380-420/sup 0/C, tetramethylene fragments to ethene about twice as it closes to form CB; the two ends of the diradical appear to be stereochemically independent, with rotations about C-C bonds much more rapid than either recombination of dissociation. Theoretical models have suggested that singlet tetramethylene may have only a shallow or no potential energy minimum. It may, however, be relatively stable on the free-energy surface: entropies of transition-state structures leading to dissociation or CB formation should be lower than for the diradical and could be different. Experimental measurement of the variation with temperature of the k(fragmentation)/k(isomerization) ratio and the extent of retention of reactant stereochemistry in the ethene product would provide direct information about the relative temperature dependence of ..delta..G+/+ for the competing exit channels. That experiment has now been performed, by using shock-tube kinetic techniques to study the competitive fragmentation and geometric isomerization reactions shown by cis-CB-1,2-d/sub 2/ over a significant range of temperature and tunable diode laser (TDL) infrared spectroscopy to determine the stereochemistry of the CB-1,2-d/sub 2/ and ethene-1,2-d/sub 2/ product samples.

• Research Organization: Colgate Univ., Hamilton, NY (USA)
• OSTI ID: 7076492
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 109:23; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
400202 -- Isotope Effects
Isotope Exchange
& Isotope Separation
ALKANES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CYCLOALKANES
DEUTERIUM
DEUTERIUM COMPOUNDS
DISSOCIATION
ENTHALPY
HEATING
HIGH TEMPERATURE
HYDROCARBONS
HYDROGEN COMPOUNDS
HYDROGEN ISOTOPES
ISOMERIZATION
ISOTOPE EFFECTS
ISOTOPES
KINETICS
LIGHT NUCLEI
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
PHYSICAL PROPERTIES
PLASMA HEATING
REACTION KINETICS
SHOCK HEATING
SHOCK TUBES
STABLE ISOTOPES
TEMPERATURE DEPENDENCE
THERMODYNAMIC PROPERTIES