Sulfur chains

Nitrogen and oxygen can be Incorporated Into the backbone such that they are surrounded by different atom types. For example, organic peroxides contain two covalently bonded oxygen atoms that form the peroxide linkage. These molecules are Inherently unstable. Two covalently bonded nitrogen atoms are also similarly unstable. These unstable structures decompose to form smaller unstable molecules that are used to start the polymerization for some types of monomers. Thus, to be incorporated implies that the molecules are found only singularly in the backbone chain. Sulfur and silicon are considered to be chain formers. They can be found in the backbone in multiple units connected covalently to molecules of the same type or with carbon. Complete molecules with a silicon backbone are possible, and molecules with multiple sulfur links incorporated into the system are common, particularly in sulfur-crosslinked rubber. 

Dimethyl disulfide and dimethyl trisulfide were identified in crayfish tail meat with the former also identified in the boiled crayfish hepatopancreas and the pasteurized crabmeat. These two straight chain sulfur-containing compounds exhibit a cooked cabbage and spoilage odor. 

Differences in the reactivity of the ring and side chain sulfur atoms are evident in the oxidation of compound 70.2 In this case only the side chain sulfur is oxidized, forming the sulfone (71). 

Aromatic compounds with side-chain sulfur donors orthometallate when the sulfur is in a thioketone , thiobenzoate ester or a thioether group . In the thioethers an additional coordinating group is required to achieve orthometallation ... 

Main-chain sulfur-containing units Poly(ditbioetbylene)... 

The oxidation mechanism of methanethiol on activated carbon fibers (ACF) in the presence of H2S and iron catalyst was proposed by Katoh and coworkers [78]. According to them the process is initiated by, which, through chain reactions with an iron catalyst involved, form OH radicals. Those radicals not only extract hydrogen from polysufide, form chain sulfur radicals, which accelerate the H2S oxidation but also oxidize DMDS formed by partial oxidation. As a product, methane sulfonic acid is expected. This mechanism is true only for the complex system with a mixed supply of the sulfur containing gases,... 

Chemical crosslinks may be obtained by randomly joining segments in already formed chains, by random copolymerization, or by end-linking functionally-terminated chains. Sulfur cures, peroxide cures, and high-energy irradiations are familiar methods of random crosslinking. Copolymerization monomers where at least one type has three or more reactive sites also lead to randomly crosslinked networks. Formation of networks by end-linking... 

Reduction of Steric Clashes Between Side Chains and the Polythiophene Backbone. Each side chain has steric contacts with the lone pairs on the sulfur atom in the backbone (Figure 1). These steric interactions induce rotation about the thiophene-thiophene bonds and decrease k orbital overlap along the backbone. Head-to-head couplings involve two side chain-sulfur lone pair interactions and result in greater steric strain.(30-32,58) There are three main methods for decreasing the steric interactions between the side chains and the polymer backbone. The first involves eliminating head-to-head couplings within the polymer. The second approach is to use side chains that are sterically less bulky than alkyls (e.g. alkoxy). 

Polysaccharides with strongly acidic residues, present as esters along the polymer chains (sulfuric, phosphoric acids, as in furcellaran, carrageenan or modified starch), are also very soluble in water and form highly viscous solutions. Unlike polysaccharides with carboxyl groups, in strongly acidic media these solutions are distinctly stable. 

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