Sulfur: characteristics compounds

Elemental sulfur is found in the flames of all the sulfur-bearing compounds discussed in the previous subsections. Generally, this sulfur appears as atoms or the dimer S2. When pure sulfur is vaporized at low temperatures, the vapor molecules are polymeric and have the formula Sg. Vapor-phase studies of pure sulfur oxidation around 100°C have shown that the oxidation reaction has the characteristics of a chain reaction. It is interesting to note that in the explosive studies the reaction must be stimulated by the introduction of O atoms (spark, ozone) in order for the explosion to proceed. 

Sulfur dioxide is a colorless gas with a sharp, pungent odor, like that of a burning match. Most people are able to detect this highly characteristic odor at concentrations of about 0.5 ppm or greater. Its chemical formula is SO2. Sulfur dioxide is readily soluble in water, forming the weak acid sulfurous acid (H2SO3). Sulfur dioxide is formed when sulfur or a sulfur-containing compound is burned ... 

The Scuppemong grape has a distinctive flavor characteristic. Kep-ner and Webb (47) analyzed the volatile essence of this grape and identified six alcohols, including 0-phenylethyl alcohol, five aldehydes, and five esters. No nitrogen or sulfur containing compounds were found which indicated the absence of methyl anthranilate. 

We would like to reiterate our initial suggestion (153) that studies of the structures of these compounds with highly hydrophobic ligands, in nonaqueous media, may reveal interesting aggregation characteristics. Such aggregations may persist in the solid state, particularly if these compounds are recrystallized from water-free, nonpolar solvents. Very little is known about the coordination properties of the alkaline earth—sulfur ligand compounds. 

Table III extends the comparison of these resids with an emphasis on reactivity, asphaltene characteristics, compound types and the refractory forms of sulfur, such as benzothiophenes and asphaltenic sulfur.

Sulfur Heterocyclics. Sulfur containing compounds (thiols, thiophenes, thiazoles,. .. etc.) play a major role in the flavor of raw and processed foods. These compounds have characteristic flavor notes and the flavor thresholds are mostly low. Several reviews (ill, 112, 113) demonstrate the important role of sulfur compounds in food flavors. Organoleptic properties of these compounds may be pleasant, strong nut-like odor of U-methyl-5-vinylthiazole which is present in cocoa (llU) objectionable pyridine-like odor of thiazole (115) quinoline-like odor of benzothia-zole (ll6) strong tomato leaf-like odor of isobutylthiazole (117) and bread crust flavor of acetyl-2-thiazoline (ll8). A mixture of oxazoles, thiazoles, thiazolines, imidazoles, trithiolanes and... 

Sun, B., Tian, H., Zheng, R, Liu, Y., Xie, J., Meaty aromas characteristic structural unit of sulfur-containing compounds with a basic meat flavor. Perf. Flav. 30(1), 36-45 (2003)... 

Unfortunately, commercially available DMSO has a characteristically objectionable odor which is caused by low-level impurities, considerably lower than 1%, largely dimethyl sulfide (DMS) but also a small number of other sulfur-containing compounds. These compounds have an effect on taste as well as smell. They are particularly measurable by UV absorption at 275 mp,. Technical Grade DMSO (pharmaceutically objectionable odor) has a UV275 > 0.25. Lowering UV275 to <0.1 makes DMSO essentially odorless. 

Under normal conditions, the concentrations of sulfur-containing compounds in human blood and breath are very low, and a high concentration is likely related to liver diseases. Compounds like ethyl mercaptan, dimethylsulflde, or dimethyldisul-fide are responsible for the characteristic odor in the breath of cirrhotic patients. 

Sulfur-containing compounds (thiols and sulfides) are easily recognized from the M -h 2 isotopic peak each sulfur contributes 4.4% to the abundance of the M -I- 2 ion. The fragmentation patterns of thiols (mercaptans) and sulfides (thioethers) parallel the corresponding alcohols and ethers. For example, similar to the alcohol series at m/z 31,45, 59,..., the a-cleavage in thiols produces a series of ions at m/z 47, 61, 75, 89,..., and each ion has a satellite peak 2 u higher, due to In addition, thiols exhibit a characteristic loss of H2S, followed by the elimination of alkene moieties to produce peaks at (M — 34)+, (M — 34 — 2114)+, and so on. In contrast, secondary thiols show a characteristic peak at (M — SH)+. Aromatic thiols also behave similarly to phenols under El conditions. In addition, they show ions at (M — S)+, (M — SH)+, and (M — 2114)+. ... 

While the occurrence of sulfur compounds is of interest, their sensory properties can be critical to the flavor of a food. According to Boelens and van Gemert (2) "most of the volatile sulfur compounds are essential constituents of the material. That means they are necessary for the sensory quality, but that they are not characteristic. A small number of the sulfur compounds, however, are characteristic compounds..." These compounds, by themselves, can be recognized as having the same... 

Elementary sulfur or compounds that can be used as a source of sulfur form together with suitable additives at higher temperatures thio-ether-, disulfide- or polysulfide-bridges in and between chains. This vulcanisation method is primarily suitable for those elastomers that have unsaturated bonds. The rubber produced by this method has good mechanical characteristics. However, a disadvantageous chemical characteristic of rubber vulcanised with sulfur is that additives can leach into the product. An example is the release of thiol compounds, which are incompatible with some mercury compounds. 

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