Mercaptans chemical structure

Fig. 2. The chemical structure of (a) prodrug diallyl disulfide (DADS), (b) aUyl mercaptan, and (c) s-allylmercaptocysteine.

Effect of Molecular Configuration of Elastomer. The extent of the impact and strength improvements of ERL-4221 depends on the chemical structure and composition of the elastomer modifier. The data shown in Table I indicate that the carboxyl terminated 80-20 butadiene-acrylonitrile copolymer (CTBN) is the most effective toughening and reinforcing agent. The mercaptan terminated copolymer (MTBN) is considerably less effective as far as tensile strength and heat distortion temperature are concerned. The mercaptan groups are considerably less reactive with epoxides than carboxyls (4), and this difference in the rate of reaction may influence the extent of the epoxy-elastomer copolymerization and therefore the precipitation of the rubber as distinct particles. 

The examples of reaction rates of O2 in Figure 12.7 show that O2 reacts only with deprotonated species (e.g., phenolate anions) that is, the apparent rate constants decrease in the pH region below the pKa of the chemical. Singlet oxygen is selective it is an electrophile that reacts only with particular functional chemical structures such as are present in 1,3 dienes (see chemical structure of fiirfuiyl alcohol) or polycondensed aromatic hydrocarbons (with delocalized 7T electron bonds) or in sulfides or mercaptans (Hoigne, 1990). 

MERCAPTAN - A compound chemically similar to alcohol, with sulfur replacing the oxygen in the chemical structure. Many mercaptans have an offensive odor and are used as deodorants in natural gas. 

Since the original observation of Lipmann et cd. (1947) on the presence of pantothenic acid in coenzyme A, the purification and chemical structure of the coenzyme has been the subject of intensive investigation in many laboratories (Snell et al., 1950 Lynen and Reichert, 1951 Novell et al, 1951 Baddiley and Thain, 1951). As formulated at present, coenzyme A contains 1 adenine, 1 ribose, 1 sulfur, and 3 phosphates per pantothenate. Evidence presented by Lynen and Roichert (1951) indicates that acetyl-CoA, which is now considered synonomous with active acetate, is an acetylated mercaptan. A tentative structure of acetyl-CoA is given below. 

The sulfides are chemically neutral they can have a linear or ring structure. For molecules of equal carbon number, their boiling points are higher than those of mercaptans they constitute the majority of sulfur containing hydrocarbons in the middie distillates (kerosene and gas oil). 

Cystine, which contains a disulfide bond, is reported to be the most numerous and reactive amino acid present in hair keratin. Disulfide bonds in cystine are reduced by mercaptans and phosphines, and oxidized by perborates, bromates, and bleach. These reactions result in structural rearrangements within keratin which may affect the physiochemical properties of hair, since disulfide bonds in cystine contribute to the stability of hair. For example, hydrogen peroxide bleaching of hair is an oxidative process which occurs readily in an alkaline medium. This results in the formation of perhydroxy anions which have been proposed to react with cystine to form cysteic acid residues. The process of bleaching results in the loss of approximately 15% of the cystine bonds originally present in keratin and may explain the increased permeability of bleached hair to chemicals. - ... 

As we recognize additional chemical types which display the H bond interaction, we find that this interaction is important in an increasing segment of our chemical knowledge. With H bonding discernible for such weak acids as mercaptans, thiophenols, and halogen-substituted alkanes, and for such we2ik bases as aromatics, olefins, and thioethers, it becomes profitable to look for even weaker interactions which have properties in common with the H bond. Just such an example has already been mentioned in Section 12.2.1 the crystal structure of aromatics provides evidence of attractive interaction between the aromatic C—H protons and the pi electrons of adjacent molecules. 

Other Studies. - The P NMR chemical shifts of alcohols, carboxylic acids and phenols phosphitylated with 2-chloro-4,4,5,5-tetramethyl-dioxaphospholane have been correlated with substituent effects of phenols. P NMR spectroscopy has also been used to study activation pathways of aryl H-phosphonate ester condensation reactions, the conversion of allenyl and divinyl phosphines to 1- and 2-phosphadienes, the reaction of tetraphosphorus decasulfide with dialkyl disulfides, the reaction of phosphine with cyclic olefins, the chemical shift tensors of powder samples of phosphole derivatives, the reactions of alcohols and mercaptans with tetraphosphorus trichalcogen diiodides, the structure of aminomethanebisphosphonic acids, and reactions of 00-di-(2-ethylhexyl)dithiophosphoric acids. ... 

Three isomers of butyl mercaptan (BYOO-til mer-KAP-tan) exist. Isomers are two or more forms of a chemical compound with the same molecular formula, but different structural formulas and different chemical and physical properties. The names and synonyms of the isomers are n-butyl mercaptan, known as l-hutanethiol, i-mercapto-butane, or n-butyl thioalcohol -butyl mercaptan, called 2-butanethiol or i-methyl-i-propanethiol and ferf-butyl mercaptan, also known as 2-methyl-2-propanethiol. The isomers have slightly different expanded chemical formulas n-butyl mercaptan, CH3CH2CH2CH2SH -butyl mercaptan, CH3CH2CH(SH)CH3 and ferf-butyl mercaptan, CH3C(CH3)(SH)CH3. The isomers have vastly differing melting points n-butyl mercaptan, —115.67 (—i76.2i°F) -butyl mercaptan,... 

In the mid-1970s, polysulfide polymer chemistry was advanced when Products Research and Chemical Corporation introduced a polyoxypropylene urethane backbone with mercaptan terminal groups [7]. Molecular weight regulation and minimization of side reactions are important features. The backbone is significantly different from that of conventional polysulfide polymers, yet the curing chemistry is the same and the eured product is a polysulfide rubber. A typical structure of this type of resin is shown below. 

Between 1960 and 1976 several new mercaptan terminated polymers having varied polymer backbones were introduced. These are covered in the section entitled Other Mercaptan Terminated Polymers. The chemical resistance of these various polymers can vary depending upon their backbone structure and, on this basis, should be evaluated on their own relative merits. 

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