Nitric Oxide Catalyzed Cis-Trans Isomerization of Dideuteroethylene

Paramagnetic Exchange Spin-Catalysis of theCis−TransIsomerization of Substituted Ethylenes

“…It is well-known that this reaction is catalyzed by paramagnetic molecules such as O 2 , NO, NO 2 , S 2 , and Se 2 . [3][4][5][6][7] The mechanism of this catalysis was treated by Eyring et al 8 from the viewpoint that a paramagnetic substance catalyzes isomerization Via the transition from the singlet (S 0 ) to the triplet (T 1 ) electronic state (path a in Figure 1) by providing "a nonhomogeneous magnetic field which will act differently on the two magnetic dipoles arising from spin of two electrons in the double bond". However, the probability of the triplet path in the absence of a catalyst is small because of the small spin-orbit coupling (SOC) between the corresponding singlet S 0 and triplet T 1 states.…”

“…However, the probability of the triplet path in the absence of a catalyst is small because of the small spin-orbit coupling (SOC) between the corresponding singlet S 0 and triplet T 1 states. 3,9,10 It has been shown 6,7,11,12 that the singlet mechanism is the only important thermal mechanism for the cistrans isomerization of pure simple olefins in the gas phase in the absence of a catalyst. However, one has to suspect the triplet mechanism as responsible for the lowering of activation energy of these reactions occurring in solution and for the catalytic and photosensitized cis-trans isomerization.…”

“…This reaction is analogous to the thermal isomerization of 1,2-dideuterioethylene which occurs in the gas phase. 3,4,6 It has been shown that the isomerization of this † Permanent address: Department of Chemistry, Cherkassy Engineering and Technological Institute, 257006, Cherkassy, Ukraine.…”

“…According to a suggestion of Eyring et al ., this reaction could pass through the singlet (path b in Figure ) or the triplet (path a in Figure ) electronic states when ethylene-type molecules isomerize from the cis to the trans form. It is well-known that this reaction is catalyzed by paramagnetic molecules such as O 2 , NO, NO 2 , S 2 , and Se 2 . − The mechanism of this catalysis was treated by Eyring et al . from the viewpoint that a paramagnetic substance catalyzes isomerization via the transition from the singlet (S 0 ) to the triplet (T 1 ) electronic state (path a in Figure ) by providing “a nonhomogeneous magnetic field which will act differently on the two magnetic dipoles arising from spin of two electrons in the double bond”.…”

Etude conformationnelle dans l'approximation CNDO/BW: barrière de rotation interne de petites molécules organiques

“…Mentionnons seulement que dans le second cas il faut tenir compte de la corr6lation Clectronique dans le calcul de la barri6re de rotation, ce qui n'est pas necessaire dans le premier cas. Rabinovitch & Looney [30] ont obtenu exp6rimentalement 65,O kcal/mol pour 1'6nergie d'isomkrisation cis-trans de 1'Cthylkne. Les calculs de Demur & Kohn [29], B l'aide de la mCthode semi-empirique MIND0/2 1311, donnent 53,46 kcal/mol, le bon accord devant &re attribuC au choix judicieux des paramktres semi-empiriques qui contiennent l'effet de corrdation Clectronique.…”