Sulphide linkages

Modified oligonucleotides containing sulphide linkages have been prepared by a dimer coupling procedure. In one approach the modified dimer is assembled from 3 -deoxy-3 -(2-hydroxyethyDribofuranosylthymine which is protected at the 5 - and 2 - positions, mesylated and... 

Producing of Crystalline Aromatic Poly ketone with Simple Ether and Sulphide Linkages. Japan Patent Application 62-530. 

Some of the sulphur from the sulphide linkages may be removed by... 

The presence of the either linkages is sufficient to allow the material to be melt processed, whilst the polymer retains many of the desirable characteristics of polyimides. As a consequence the material has gained rapid acceptance as a high-temperature engineering thermoplastics material competitive with the poly-sulphones, poly(phenylene sulphides) and polyketones. They exhibit the following key characteristics ... 

Fig. 1.2 Crystal structures of the major sulfides (metal atoms are shown as smaller or black spheres) (A) galena (PbS) structure (rock salt) (B) sphalerite (ZnS) structure (zinc blende) (C) wurtzite (ZnS) strucmre (D) pyrite structure and the linkage of metal-sulfur octahedra along the c-axis direction in (/) pyrite (FeSa) and (//) marcasite (FeSa) (E) niccolite (NiAs) structure (F) coveUite (CuS) structure (layered). (Adapted from Vaughan DJ (2005) Sulphides. In Selley RC, Robin L, Cocks M, Plimer IR (eds.) Encyclopedia of Geology, MINERALS, Elsevier p 574 (doi 10.1016/B0-12-369396-9/00276-8))...

Although many types of dye contain sulphur other than in sulphonic acid groups, sulphur dyes are usually considered to be those dyes that are best applied from a sodium sulphide dyebath. Like vat dyes, sulphur dyes are water-insoluble before and after application to cellulosic fibres. Disulphide linkages in the dye molecules are readily reduced by sodium... 

The first commercial sulphur dye was discovered accidentally in 1873 by Croissant and BretonniSre who heated lignin-containing organic waste, such as sawdust, with sodium polysulphide at about 300 °C the product was sold under the name Cachou de Laval [52]. Even today an equivalent dye (Cl Sulphur Brown 1) is derived from lignin sulphonate, which is readily available from waste liquors from wood pulp manufacture. The real pioneer of sulphur dyes was Vidal, the first chemist to obtain dyes of this type from specific organic compounds. In particular, Sulphur Black T (Cl Sulphur Black 1) was made from 2,4-dinitrophenol in 1899. At the turn of the century many of the intermediates available were subjected to sulphurisation (thionation), that is, treatment with sulphur, sodium sulphide or sodium polysulphide to introduce sulphur linkages. 

The inherent hydrophobicity once thought to be typical of sulphides (Ravitz and Porter, 1933) is now thought to be restricted to sulphides such as molybdenite (Chander et al., 1975) and other minerals or compound with special structural feature (Gaudin et al, 1957b). Common commercial sulphide minerals, which are needed to recover in flotation, are normally composed of anion (S ) and heavy metal ions such as Cu, Cu, Pb, Zn, Hg, Sb, Bi transitive metal ion such as Fe, Co, Ni and noble and rare metal ions such as Ag, Au, Mo. On the basis of structural pattern or mode of linkage of the atoms or polyhedral imits in space, Povarennyk (1972) introduced a crystallochemical classification of sulphide minerals, which have six major patterns as shown in Table 1.1. 

As shown by the eqns. (20-24) owing to the activity of the sulphide or polysul-phide ion, the 0—N linkage is broken to form alkoxide and thionitrate or polythio-nitrate ions. In the other reactions the influence exerted by sulphide on the oxygen atom, which results in the creation of nitrite ions, has been taken into account. Both schemes indicate that the nitrite ion is not produced by the reduction of the nitrate ion. 

If a wool fibre be immersed under tension in water at 100 C for one hour it will become distorted permanently in other words, will have acquired a permanent set. Binding forces of a more powerful nature than hydrogen bonds must have been created. The explanation proposed by Speakman Nature, 1933, 132, 930) was that the water severs the cystine linkage with the formation of sulphenic acid and sulphide radicals ... 

The characteristic feature of the dyes of this class is that they all contain sulphur linkages within their molecules. They are usually insoluble in water, but dissolve in a solution of sodium sulphide to which sodium carbonate may or may not be added. The sodium sulphide acts as a reducing agent, severing the sulphur linkage and breaking down the molecules into simpler components which are soluble in water and substantive towards cellulose. 

The above mentioned authors also established that the nitrate ion (in contrast with the nitrite ion) slowly undergoes reduction in the presence of sodium hydro-sulphide. This leads to the conclusion that the nitrite ion formed during the hydrolysis of nitric esters caimot be produced by the reduction of a nitrate ion. Hence if the nitrite ion is formed direct during the hydrolysis of nitric esters, then it could only be produced by breaking the linkage between the oxygen and nitrogen atoms. 

In this process, the ring strain of the monomer is relieved when the ring is broken into a linear structure, covalently and sequentially linked in the presence of a catalyst (initiator). There is no loss or gain of any atom or group. The monomer rings have ether, amide, anhydride, sulphide or other linkages. 

The trioxides can all be obtained by reacting the elements or their sulphides in air (Table 4.13). They show increasing thermal stability and basic character, but reluctance to oxidise to the pentava-lent state, on progressing from P to Bi. Although less soluble in water than its phosphorus analogue (Table 4.11), AS4O6 eventually produces arsenous acid As(OH)3 Unlike phosphorous acid, however, the latter compound does not exist in tetrahedral form with an As-H linkage. 

Phosphorus sulphide hydrolyses are complex processes involving the initial rupture of P-S-P followed by the P-P linkages (where present), and the eventual replacement of S by O. There have been conflicting reports about the nature of the products, which depend on pH, temperature and other factors. 

Desulphurisation of a diphosphine sulphide by heating with a metal is another good method (Figure 9.24), and in some circumstances P-N linkages can be replaced by P-P (6.664). Diphosphines are also formed from silyl phosphines (Figure 9.10) and by disproportionation of dimethylphosphi-nous fluoride (6.175) and of more complex phosphines. An uncommon reaction is the decomposition of mercury ter-butyl phosphide by ultraviolet radiation in benzene solution (6.665). At low temperatures some unsymmetrical derivatives can be formed (6.666). 

Notable amongst As/P compounds (i.e. devoid of As-P linkages) are mixed AsO " /PO " minerals, arsenatophosphates based on As-O-P linkages (Chapter 5.4), ionic salts such as Ph4p (AsNj) , and substituted phosphorus sulphides (Chapter 4.3). 

The substitution of As for P in any compound with P-P linkages is possible, at least in principle. Amongst the simplest known examples are white phosphorus derivatives P4. As , the black phosphorus derivative AsP, AS2P and the mixed sulphides P4. tAS tS3 (Chapter 4.3). Grey arsenic and black phosphorus have been reported as forming limited solid solutions, but the composition P20AS is believed to consist of ordered chains of P atoms as in Hittorf s phosphorus. The As atoms occupy special positions which allow them to link these adjacent chains. 

The tertiary phosphine sulphides, R3PS contain a single terminal P=S linkage. One of the simplest and best methods of preparation is the direct reaction of the tertiary phosphine with elemental sulphur (6.74). The reaction, normally exothermic, is carried out in benzene or carbon disulphide with moderate... 

Weber, E., Polytropic cation receptors. 2. Synthesis and selective complex formation of spiro-linked multitrop crown compounds,/. Org. Chem., 47, 3478, 1982. Goldberg, 1., Geometry of the ether, sulphide and hydroxyl groups and structural chemistry of macrocyclic and noncyclic polyether compounds, in The Chemistry of the Ether Linkage, Patai, E., Ed., Suppl. E, Part 1, Wiley, London, 1981, 175. 

The Sulphur Cycle.— Unlike phosphorus, sulphur appears in both oxidised and reduced forms in the history of life. Completely oxidised as sulphate, it enters the plant from the soil, and is converted into partially reduced organic compounds containing the thiol group —SH or the disulphide linkage —S—S—. From these, the completely reduced form, HjS, is derived by bacterial degradation either in the soil or in the alimentary tract of the animal. Hydrogen sulphide is attacked by the sulphur-oxidising bacteria, with the ultimate formation of sulphate, which is available for plant absorption. 

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