Functional properties, sulfur compounds

The chemistry of saturated heterocyclic compounds is characteristic of their functional group. For example, nitrogen compounds are amines, oxygen compounds arc ethers, sulfur compounds are sulfides. Differences in chemical reactivity are observed for three-membered rings, e.g., epoxides, whose enhanced reactivity is driven by the relief of their severe ring strain. This chapter discusses heterocycles that are aromatic and have unique chemical properties. 

Figure 2. Radioactivity chromatogram of sulfur compounds derivatized with monobromobimane. The reversed-phase HPLC separation is based on the hydrophobic properties of the bimane-sulfur adducts but peak area is based on "S-radioactivity of the compounds. At time 0 sulfite and thiosulfate impurities are present before addition of the hepatopancrease tissue homogenate. This was a 60 min experiment to determine the sulfide detoxifying functions of the hepatopancrease of the hydrothermal vent crab Bythograea thermydron. During this time the proportion of radioactivity in sulfide rapidly decreases and thiosulfate and sulfate accumulate as end products. Two intermediates, pi and p2 accumulate then decrease during the experiment. The two intermediates are believed to be polysulfides based on similar elution times of polysulfide standards. (Figure is the unpublished chromatograms from the data in Vetter et al. (24)-) continued on next page.

Figure 5 The generic phase diagram of the (TMfjX as a function of pressure or anion substitution. On the left, the normal phase of sulfur compounds can be described as a Luttinger liquid that becomes gapped in the charge sector (LL, ) below Tj, and can develop either a spin-Peierls (SP) or localized antiferromagnetic ordered state. Under pressure, the properties of the sulfur series evolve toward those of the selenides for which the normal state shows a progressive restoration of a Fermi liquid (FL) precursor to antiferromagnetism (AF) and superconductivity (S), after [28].

The function of sulfuric acid in nitrations is to absorb the water formed, thus preventing the dilution of nitric acid. Another useful purpose of sulfuric acid is its solvent property for many organic compoxmds. In some cases the first action of sulfuric acid is to sulfonate. The sulfonic acid groups are subsequently replaced by nitro groups. Due to their insolubility in water, nitro compounds are rather easily separated by dilution of the nitrated mixture. 

Occasionally, confusion arises regarding the applicability and expectations surrounding the use of sterilants and preservatives. Properly administered in correct amounts, a sterilant can be expected to kill 100% of the viable cell population regardless of species. Preservatives, on the other hand, may cause cell death, but, in general, function to inhibit specific populations of microorganisms. Thus, the use of preservative such as SO2 and sorbic and benzoic acids should not be expected to be a carte blanche remedy for control of microorganisms present in the wine at bottling. Other distinctions between the two classes of compounds may also be drawn. The antimicrobial properties of compounds like sorbic acid and sulfur dioxide resides in the undissociated, rather than the ionized, molecule. Thus, inhibitory activity is enhanced at lower pH (Zoecklein et al., 1995). A sterilant, such as DMDC, does not rely on pH for enhanced/diminished activity. 

While the sensory properties of sulfur compounds have been of interest for many years, recent attention has focused more heavily on some of the other functional properties of these compounds. Certain sulfur compounds have been found to have antioxidative, antimicrobial, and human medicinal properties. 

The chemistry of sulfur compounds in foods is very complex and continues to be extensively studied. Both cooked and uncooked foods contain organoleptically important sulfur-containing compounds. Conversely, the off-odors of numerous foods have been attributed to sulfur compounds. In addition to their sensory properties, recent work has been increasingly geared towards other functional properties of these compounds, especially antioxidant, antimicrobial, and anticarcinogenic effects. These areas will, no doubt, continue to be the subject of research for years to come. 

We have previously reported on the excellent properties of the mustard-type sulfur compound 12 (Fig. 11.3) as a scaffold for the synthesis of functional molecules. The nucleophilic displacement of the chlorides in 12 occurs in high efficiency with a variety of nucleophiles using on water conditions. These reactions occur via episulfonium ion intermediates, and are therefore uniquely assisted by the aqueous medium. ... 

---