Alkane sulfuration

Sulfur reacts with alkanes to either dehydrate (eq. 1), oxidize, forming carbon disulfide and hydrogen sulfide (eq. 2), or cyclize, forming thiophenes (eq. 3). The products of alkane sulfurization depend on the temperature, the time at the temperature, and the stmcture of the hydrocarbon (1). 

Generally, unsaturated compounds, eg, alkenes and natural fats and their derivatives, are much more reactive toward sulfur than alkanes. Sulfur reacts with unsaturated compounds at temperatures of 120—215°C, forming products that are usually dark and often viscous cross-linked mixtures of dithiole-3-thiones (eq. 4) (2) and sulfides (Table 1) (3). 

Some anionic surfactants are used as dish-washing liquids and are made from sulfated alkanes (sulfuric esters of saturated alcohols) with 10-16 carbon atoms. Their industrial production exceeds 1000 000 tonnes per annum. 

Alkanethiols and other sulfur-bearing hydrocarbons covalently attach to metal surfaces alkanethiol onto gold is the most widely studied of these systems [27-29,31,32,45]. These SAMs are ordered provided the alkane chain contains nine or more carbons [32]. Binary solutions of two alkanethiols also appear... 

Catalytic hydrogenation is mostly used to convert C—C triple bonds into C C double bonds and alkenes into alkanes or to replace allylic or benzylic hetero atoms by hydrogen (H. Kropf, 1980). Simple theory postulates cis- or syn-addition of hydrogen to the C—C triple or double bond with heterogeneous (R. L. Augustine, 1965, 1968, 1976 P. N. Rylander, 1979) and homogeneous (A. J. Birch, 1976) catalysts. Sulfur functions can be removed with reducing metals, e. g. with Raney nickel (G. R. Pettit, 1962 A). Heteroaromatic systems may be reduced with the aid of ruthenium on carbon. 

Sulfides are sulfur analogs of ethers they contain the C—S—C func tional group They are named as al/cylthw derivatives of alkanes m sub stitutive lUPAC nomenclature The functional class lUPAC names of sul tides are derived m the same manner as those of ethers but the concluding word is sulfide... 

Elemental sulfur reacts with alkanes such as cyclopentane in the presence of superacidic trifluoromethanesulfonic acid to give symmetrical dialkyl sulfides in moderate yields. 

Orga.nic Chemistry. The organic chemistry of sulfur dioxide, particularly as it relates to food appHcations, has been discussed (246). Although no reaction takes place with saturated hydrocarbons at moderate temperatures, the simultaneous passage of sulfur dioxide and oxygen into an alkane in the presence of a free-radical initiator or ultraviolet light affords a sulfonic acid such as hexanesulfonic acid [13595-73-8]. This is the so-called sulfoxidation reaction (247) ... 

Simultaneous treatment of an alkane with sulfur dioxide and chlorine affords a sulfonyl chloride, eg, hexylsulfonyl chloride [14532-24-2] and is referred to as chlorosulfonation or the Reed reaction (247,248). 

This method is also used with alcohols of the stmcture Cl(CH2) OH (114). HaloaLkyl chlorosulfates are likewise obtained from the reaction of halogenated alkanes with sulfur trioxide or from the chlorination of cycHc sulfites (115,116). Chlorosilanes form chlorosulfate esters when treated with sulfur trioxide or chlorosulfuric acid (117). Another approach to halosulfates is based on the addition of chlorosulfuric or fluorosulfuric acid to alkenes in nonpolar solvents (118). 

The mechanisms for the reaction of sulfur with alkanes and unsaturated compounds are highly speculative, being strongly influenced by the specific stmcture of the substrate and by the conditions (particularly temperature) of reaction. Alkane (4), olefin (5), animal fat (6), and vegetable oil (7) sulfurization have been extensively studied because these reactions are models for vulcanization. Moreover, the products are used as lubricant additives. 

Rigorous hydrogenating conditions, particularly with Raney Nickel, remove the sulfur atom of thiophenes. With vapor-phase catalysis, hydrodesulfurization is the technique used to remove sulfur materials from cmde oil. Chemically hydrodesulfurization can be a valuable route to alkanes otherwise difficult to access. 

Poly(vinyl nitrate) has been prepared and studied for use in explosives and rocket fuel (104,105). Poly(vinyl alcohol) and sulfur trioxide react to produce poly(vinyl sulfate) (106—111). Poly(vinyl alkane sulfonate)s have been prepared from poly(vinyl alcohol) and alkanesulfonyl chlorides (112—114). In the presence of urea, poly(vinyl alcohol) and phosphoms pentoxide (115) or phosphoric acid (116,117) yield poly(vinyl phosphate)s. 

Aromaticity is the most important property of a carbon black feedstock. It is generally measured by the Bureau of Mines Correlation Index (BMCI) and is an indication of the carbon-to-hydrogen ratio. The sulfur content is limited to reduce corrosion, loss of yield, and sulfur in the product. It may be limited in certain locations for environmental reasons. The boiling range must be low enough so that it will be completely volatilized under furnace time—temperature conditions. Alkane insolubles or asphaltenes must be kept below critical levels in order to maintain product quaUty. Excessive asphaltene content results in a loss of reinforcement and poor treadwear in tire appHcations. 

Materials that are corrosion resistant to the expected cathodic polarization qualify as impressed current cathodes. Austenitic CrNi steels are used with strong acids. The oleum (i.e., fuming sulfuric acid) and concentrated sulfuric acid tanks used in sulfonating alkanes and in the neutralization of sulfonic acids are anodi-cally protected using platinized brass as cathodes [15]. Lead cathodes are used to protect titanium heat exchangers in rayon spinning baths [16]. 

A substantial portion of fhe gas and vapors emitted to the atmosphere in appreciable quantity from anthropogenic sources tends to be relatively simple in chemical structure carbon dioxide, carbon monoxide, sulfur dioxide, and nitric oxide from combustion processes hydrogen sulfide, ammonia, hydrogen chloride, and hydrogen fluoride from industrial processes. The solvents and gasoline fractions that evaporate are alkanes, alkenes, and aromatics with relatively simple structures. In addition, more complex... 

Reactions of alkanedicarboxylic acids with sulfur tetrafluoride afford, in general, mixtures of bis(trifluorQmethyI)allcanes, cyclic 0(,a,a, a -tetrafluoro ethers, linear bis(pentafluoroalkyl) ethers, and polyfluoroethers The cyclic ethers constitute the major products of the reactions with alkane-1,2 dicarboxyhc acids, they are also formed in the reactions with alkane-1,3-dicarboxylic acids but not with 1,1- nor 1,4-dicarboxylic acids [211] (equation 105)... 

An illustration of the tendency of alkane 1,2- and alkane-1,3-dicarboxylie acids to a ring closure during the reaction with sulfur tetrafluoride is the reaction of propane-1,2,3-tricarboxylie acid The corresponding six- and five-membered cyclic ethers are formed in a 1 4 ratio [211] (equation 106)... 

Oxidative reactions frequently represent a convenient preparative route to synthetic intermediates and end products This chapter includes oxidations of alkanes and cycloalkanes, alkenes and cycloalkenes, dienes, aromatic fluorocarbons, alcohols, phenols, ethers, aldehydes and ketones, carboxylic acids, nitrogen compounds, and organophosphorus, -sulfur, -selenium, -iodine, and -boron compounds... 

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