Sulfides bond strength

Nitride, fluoride and sulfide bond strength and bond length variations... 

Fig. 11. Effect of polyolefin primers on bond strength of ethyl cyanoacrylate to plastics. All assemblies tested in accordance with ASTM D 4501 (block shear method). ETFE = ethylene tetrafluoroethylene copolymer LDPE = low-density polyethylene PFA = polyper-fluoroalkoxycthylene PBT = polybutylene terephthalate, PMP = polymethylpentene PPS = polyphenylene sulfide PP = polypropylene PS = polystyrene PTFE = polytetrafluoroethylene PU = polyurethane. From ref. [73].

Both CIS- and trans-l-arylsulfonyl-2-arylsulfenyl propenes (56) underwent a Smiles rearrangement under electron impact at 20 and 70 eV and formed a diarylsulfide ion [M — 104] (equation 27a) through a process where a bond between the R QH4 group and the sulfide sulfur is formed and a rearomatization occurs by a loss of the neutral thiirene dioxide or a simultaneous expulsion of SO2 and propyne. The ion m/z 148 was also obtained from all of the sulfonyl-sulfides, 56 (equation 27b) and here the loss of seemed to be related to the bond strength . In addition to the above compounds 56 exhibited some simple cleavages before and after sulfone-sulfinate rearrangements. 

A theoretical foundation for understanding these correlations is found in the calculated bulk electronic structures of the first- and second-row TMS. The electronic environment of the metal surrounded by six sulfur atoms in an octahedral configuration was calculated, using the hypotheses that all the sulfides could be represented by this symmetry as an approximation. There are several electronic factors that appear to be related to catalytic activity the orbital occupation of the HOMO (Highest Occupied Molecular Orbital), the degree of covalency of the metal-sulfur bond, and the metal-sulfur bond strength. These factors were incorporated into an activity parameter (A2), which correlates well with the periodic trends (Fig. 16) (74, 75). This parameter is equal to the product of the number of electrons contained in the... 

The use of Mn-salen catalysts for asymmetric epoxidation has been reviewed.30 Oxo(salen)manganese(V) complexes, generated by the action of PhIO on the corresponding Mn(III) complexes, have been used to oxidize aryl methyl sulfides to sulfoxides.31 The first example of C—H bond oxidation by a (/i-oxo)mangancsc complex has been reported.32 The rate constants for the abstraction of H from dihydroanthracene correlate roughly with O—H bond strengths. 

In the case of conventional construction sealants, the poly sulfides, polyurethanes, epoxies, and acrylics have all shown various degrees of sensitivity to moisture. Hydrolysis causes the breaking of bonds within the sealant. Thus, the bond strength decreases and cohesive failure results. However, before this occurs, the sealant usually swells and may cause deformation or bond failure before hydrolysis can completely take action. 

In industrial practice, catalytic surfaces are often very complex, not only structurally but also chemically. An example is shown in Fig. 1 from Chianelli et al. [6] for hydrodesulfurization catalysts. The data indicate that maximum dibenzothiophene hydrodesulfurization activity is achieved at intermediate heats of formation of metal sulfides, i.e., at intermediate metal-sulfur bond strengths. Again, while such surface energetic considerations do not have ab initio predictive ability, they are valuable tools for catalyst synthesis and prescreening. 

A catalyst is usually requires in the formation of H2S. Metal sulfides are the most common catalysts used in the laboratory or in large-scale production of H2S. The catalytic activity of metal sulfides is linked to the metal-sulfur bond strength. 

As one would expect from the respective bond strengths, the order for the halides is R-I > R-Br R-Cl for the same R group and selenides react faster than sulfides for the chalcogenides. In general, when the bond strengths are comparable, monovalent halides tend to be more reactive than divalent... 

Different fi-om C-tracer studies, these being connected mostly with reaction mechanism problems, sulfur isotopes are connected with apph-cations to the role of sulfur in solid catalysts to a great extent. This is connected with the wide application of sulfide catalysts. Metal-sulfur bond strengths are substantially ( 100kJ/mol) larger than those of the... 

The most general observation is to be made on the basis of the tracer studies that only a part of surface sulfur is mobile or exchangeable on catalysts with sulfides and oxides. Supported Co and Ni contain only mobile sulfur, if sulfided by thiophene and contain both mobile and immobile sulfur, if they are sulfided by H2S/H2.[ 1 This is interpreted with the differences in the metal-sulfur bond strengths, as the edge S-atoms are held more weakly than the top S-atoms of the slab.I This follows from the results of some radiosulfur tracer studies of metal single crystals that different surface S-species are formed at different surface sulfur concentrations, and on different crystal faces of Pt, and... 

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