ISSN:
1432-2234
Keywords:
Diimide
;
dissociation of ∼
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract Parts of the potential energy surface of N2H2 have been studied using CASSCF- and contracted CI-methods. Of particular interest was the concerted dissociation of cis- and trans-diimide into N2 and H2, since the trans-dissociation is symmetry allowed and the cis-dissociation forbidden. Three different saddle points were located, of which only one, of C 2υ- symmetry, is a true transition state. Elaborate numerical gradient methods using exact Hessians and update procedures had to be used to find these saddle points on the unexpectedly complex N2H2-surface. The barrier height with respect to trans-diimide is 61 kcal/mol after vibration correction. Since this energy is higher than the barrier for interconversion, cis- and trans-diimide have the same transition state. It is further found that diimide preferably dissociates stepwise, by losing one hydrogen at a time, rather than in a concerted way. This conclusion is drawn basically because the geometry of the transition state for the concerted dissociation has a very long H-H distance of 5.6 a.u. The N-H bond energy in trans-diimide is 56 kcal/mol after vibration correction.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00549671
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