Sulfides, bond energies

Table 1 Molecular parameters of the diatomic oxides and sulfides of carbon and silicon derived experimentally (force constant f and bond energy BE) and theoretically (bond distance d, charge Q, and Shared Electron Number SEN).

The difference in reactivity between the a-stannyl sulfide 16A and the a-silyl sulfide 16B can be explained by comparing the two-center energies of their carbon-metal bonds. Semiempirical molecular orbital calculation revealed that the bond energies decrease in the order of 2-silyl, 2-germyl, and 2-stannyl-1,3-dithiane cation radicals. As the silyl dithiane was completely consumed by the oxidation under the... 

The presence of any of several functional groups is likely to impart photolability to drug molecules. These include carbonyl (C=0), nitroaromatic, -N-oxide, -alkene (C=C), aryl chloride, weak C-H and O-H bonds, sulfides, and polyenes. Some of these functional groups impart photolability as a result of their chromophoric properties (e.g., carbonyl) and some of them impart photolability by virtue of their weak covalent bonds, (e.g., O-H bonds). A list of several common bonds and their respective bond energies (E ) and the corresponding wavelengths ( ) are presented in Table 1. 

Hydrogen sulfide Chemical bonding energy Electrocatalytic... 

The order of increasing thermal stability of sulfur compounds is sulfides, disulfides, mercaptans, and thiophenes, which is consistent with the fact that mercaptans predominate in petroleum products that have been thermally treated and that increasing concentrations of thiophenes are found as the thermal conditions become more severe (117). This same order may be observed, for three of the sulfur compound types, in the average bond energy data presented by Remick (130) ... 

The large difference in mono-sulfidic bonds is the main contributor to increased network stiffness with increased sulfur concentration. Mono-sulfidic bonds also have the highest bond energy of the three. The large difference in poly-sulfidic bonds is a probable contributor to poor network ageing at the higher sulfur concentration (5). 

The above has allowed the author, Tolstopyatova, and Naumov (390) to eonelude that the bond energies of the atoms of the organic substrates with the surface of oxide catalysts found by the kinetic method, are chiefly organometallic. Probably, this conclusion can be extended to sulfides, selenides, nitrides, borides, and hydrides of metals. 

Eyring and Wadsworth (50) and Little (51) present spectroscopic evidence that thiols bond to ZnO surfaces and xanthates bond to PbS surfaces by way of hydroxyl-exchange reactions in which metal-sulfide bonds are formed, and metal-hydroxyl bonds are broken during adsorption. We expect that trends exhibited in the relative stabilities of amino acid and hydroxo complexes of various dissolved cations should parallel trends in the relative reactivities and adsorption free energies, should this type of bonding control adsorption. 

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