Deoxygenation and desulfurization of cyclic ethers and thioethers by carbon atoms. Intermediates with excess energy in a low-temperature matrix

Abstract

Singlet carbon atoms react with cyclic ethers to give carbon monoxide and diradical species. Cyclic thioethers react with singlet carbon atoms to give carbon monosulfide (CS) and diradicals. While both deoxygenation and desulfurization are facile processes, the deoxygenation reaction is more exothermic; this exothermic-

Mechanism of hydrogenolysis and isomerization of oxacycloalkanes on metals, XVI. Transformation of tetrahydrofuran on platinum catalysts

“…The reaction leading to butane formation has been termed "hydrodeoxygenation" as well as "deoxygenation". The former of the two seems more adequate [19] considering that "deoxygenation" has mainly been used for the designation of the conversion of epoxides accompanied by olefm formation [20], As regards the role of supports, we offer to consider the following experimental data too. It is well-known that propylene oxide is isomerized to propionaldehyde and acetone by oxide catalysts [21].…”

Reactions of 1S, 1D, and 3P carbon atoms with water. Oxygen abstraction and intermolecular formaldehyde generation mechanisms; An MCSCF study

“…1 DE a ¼ RT ln (47) with T ¼ 300 K, using simple collision theory result modified by a Boltzmann factor.…”

“…Apparently coupling to the argon matrix is weak, yielding a product distribution as if the reactions are proceeding in the gas phase. Similarly, in reactions of carbon with cis-and trans-2-butene oxide at 77 K, Skell et al concluded that excess energies of some intermediates were not easily absorbed by the frozen matrix [47]. On the other hand, in reactions of arc generated carbon with a surplus of H 2 O at 77 K, formaldehyde was observed [2, 26b].…”

Carbon, Silicon, Germanium, Tin, and Lead (Group IVA)

“…58 ' 59 The intermediacy of CS in a similar C 1 + CS 2 reaction was demonstrated by 0 2 trapping to form COS. This species existence in the matrix was also implied by the formation of (C-S) n polymer upon matrix warm-up.…”

“…These types of nonstereospecific reactions and cleavages suggested that the intermediate species possessed excess vibrational and/or electronic energy in the matrix. 58 Thus, it was of interest to study a similar but less exothermic abstraction process, that of desulfurization by C 1 (Ci deoxygenation ~85-100 kcal excess, C x desulfurization -45 kcal excess 58 ). Indeed, analogous desulfurization of episulfides yielded much more stereospecific reactions, and in the case of tetrahydrothiophene some…”