Preparation of sulfides

Sulfides, compounds of the type RSR, are prepared by nucleophilic substitution reactions. Treatment of a primary or secondary alkyl halide with an alkanethiolate ion (RS ) gives a sulfide  

It is not necessary to prepare and isolate the sodium alkanethiolate in a separate operation. Because thiols are more acidic than water, they are quantitatively converted to their alkanethiolate anions by sodium hydroxide. Thus, all that is normally done is to add a thiol to sodium hydroxide in a suitable solvent (water or an alcohol) followed by the alkyl halide. 

Which alkene, c/s-2-butene or frans-2-butene, would you choose in order to prepare meso-2,3-butanediol by epoxidation followed by acid-catalyzed hydrolysis Which alkene would yield meso-2,3-butanediol by osmium tetraoxide dihydroxylation  

Many naturally occurring substances are epoxides. In most cases, epoxides are biosynthesized by the enzyme-catalyzed transfer of one of the oxygen atoms of an O2 molecule to an alkene. Because only one of the atoms of O2 is transferred to the substrate, the enzymes that catalyze such transfers are classified as monooxygemses. A biological reducing agent, usually the coenzyme NADH (Section 15.10), is required as well. 

A prominent example of such a reaction is the biological epoxidation of the polyene squalene. 

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Vecht, A. Davies, D. A. Smith, D. 1998. A novel method for the preparation of sulfides and selenides and its apphcation for phosphor synthesis. Mat. Res. Innovat. 

Thiols (RSH) cleave a( the sulfur-hydrogen bond on irradiation, and this allows the preparation of sulfides by subsequent radical addition to an alkene (5.62). Hydrogen sulfide behaves in the same way (5.631, and long-chain thiols are made commercially for use as modifiers in emulsion polymerization. 

The rare earth sulfites have potential applications in thermochemical cycles and as starting materials for the preparation of sulfides which can be formed by the reduction of sulfites, e.g., by CO.15,16 One problem is that the anhydrous sulfites apparently cannot be synthesized directly, but only by the dehydration of hydrates. Thus, great care must be taken to avoid decomposing the salt while water is removed, frequently by removal of S02. The decomposition product is frequently an oxysulfate, or sulfite-sulfate, e.g., Ce2(S03)2S04 and Ce2S03(S04)4. Listed are several references which will provide the reader with entry into the field, many by workers at Helsinki University.16 19... 

Dibenzyl trisulfide provides a useful source of sulfur for the preparation of sulfide anions via oxidative replacement of R8 ligands (equation 38). [Fe2(/r-82)(85)2] contains two Fe85 rings bridged by two 8 anions. 

The Transition Metal Sulfides are a group of solids which form the basis for an extremely useful class of industrial hydrotreating and hydroprocessing catalysts. Solid state chemistry plays an important role in understanding and controlling the catalytic properties of these sulfide catalysts. This report discusses the preparation of sulfide catalysts, the role of disorder and anisotropy in governing catalytic properties, and the role of structure in the promotion of molybdenum disulfide by cobalt. 

The preparation of sulfides by reaction of sulfenyl chlorides with compounds containing acidic hydrogen has been reported by Brintzinger and his coworkers in a series of papers.256 Sulfides of the indole series257 as well as (alkylthio)phenols and (alkylthio)phenyl ethers258 have been prepared by this method. 

Fission of the C-S bond of thiols can occasionally be utilized for preparation of sulfides ... 

Preparation of sulfides The reaction of the nucleoside adenosine (1.1 mmole) with dimethyl disulfide (10 mmole) and tri-n-butylphosphine (10 mmole) in DMF at 25° gives 5 -S-methylthio-5 -desoxyadenosine (2) in 73% yield. The reaction is general for desoxynucleosides and disulfides. This reaction... 

Similar reactions were also employed for preparation of sulfide- and sulfone-containing bis(naphthalic anhydrides). Thus, the interaction of 4-bromo-naphthalic anhydride with sodium sulfide yields 4,4 -sulfide-bis(naphthalic anhydride) [92, 93] ... 

One of the most significant methods for the preparation of sulfides in the u-triazoles involves the rearrangement of S-amino-l,2,3-thiadiazoles (8.1-8) under basic conditions (Eq. 15). It was later suggested that the 8.1-8 structure is an intermediate in the reactions of isothiocyanates (8.1-9) with diazomethane (Eq. 16). This reaction, with various 8.1-8 compounds, has been extended with promising results, but the problem of product structure (compare 8.1-11 and 8.1-12 with 8.1-10 and Equation IS) remains to be examined (Eqs. 17, 18). 

Simple reactions of hydrogen sulfide with CpjLn (Ln=Sm,Eu,Yb) in THF can be used for the preparation of sulfides LnS [119], which are interesting as semiconductors. This route is evidently suitable for Ln(III) sulfides. 

In this chapter, we review the sol-gel processing of sulfides in bulk, powder and thin film forms, according to four different methods of preparation of sulfides and thin films in particular, we discuss and evaluate the prospects for development of sulfide optical films for planar waveguide stmctures. 

Several works have been published on the preparation of sulfides from inorganic compounds. Table 11-1 lists some metal sulfides prepared by colloidal chemical processes. Compared with the sol-gel preparation of GeS films via route C, these metal sulfides are more stable than their oxides. Usually, nanosized metal sulfide particles were used to make sulfide films and bulk gels. Malier et al. (1998) reported the preparation of concentrated sols and transparent stiff gels of 11-Vl semiconductor nanocrystals. Sol stabilization and gelation control are achieved through successive passivation and depassivation of the surface of the nanocrystals, which are complexed with thiols. Thin films, as well as monoliths, could be prepared in this way. 

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