- Thermolysis of (1R,2R)-1,2-Dideuteriocyclobutane. An Application of Vibrational Circular Dichroism to Kinetic Analysis
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The relative rates of geometric isomerization to racemization have been studied for the title compound by using a combination of infrared (IR) and vibrational circular dichroism (VCD) spectroscopies, respectively.The results are interpreted with a kinetic and mechanistic scheme which parallels that used by Berson, Pedersen, and Carpenter on a similar study of chiral cyclopropane-d2 thermolysis.Relative rates of isomerization to stereomutation of 1.5+/-0.4 were obtained which can be interpreted to be consistent with a mechanism best described by random methylene rotation in tetramethylene-d2.This is the first application of VCD to kinetic analysis, and the advantages of IR techniques over the more usually employed UV spectroscopies to this type of basic mechanistic problem are illustrated.
- Chickos, James S.,Annamalai, A.,Keiderling, T. A.
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p. 4398 - 4402
(2007/10/02)
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- Synthesis and Thermal Decomposition of cis-3,4,5,6-Tetrahydropyridazine-3,4-d2. Relative Rates of Rotation, Cleavage, and Closure for Tetramethylene
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The stereospecific syntheses of cis-3,4,5,6-tetrahydropyridazine-3,4-d2 (6) and cis- and trans-cyclobutane-1,2-d2 are reported.The thermal decomposition of cis-3,4,5,6-tetrahydopyridazine (6) (gas phase, 439 deg C) affords 67.1 +/- 0.9percent cis-ethylene-1,2-d2, 16.1 +/- 0.8percent trans-ethylene-1,2-d2, 9.4 +/- 0.4percent cis-cyclobutane-1,2-d2, and 7.4 +/- 0.4percent trans-cyclobutane-1,2-d2.The relative rates of rotation, cleavage, and closure for this 1,2-diazene generated tetramethylene-d2 are k(cleavage)/k(closure) = 2.2 +/- 0.2 and k(rotation)/k(closure) = 12 +/- 3.An extra stereospecific cleavage component (46percent) superimposed on the 1,4-biradical pathway (54percent) from the parent tetrahydropyridazine was found, similar to that observed in the 3,4-dimethyl-3,4,5,6-tetrahydropyridazine thermal reactions.Finally, the experimental data fot the parent 1,4 biradical, tetramethylene, are compared to calculated values in the literature.
- Dervan, Peter B.,Santilli, Donald S.
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p. 3863 - 3870
(2007/10/02)
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