Carbonyl sulfide formation

The metabolic formation of carbonyl sulfide from carbon disulfide was confirmed in an in vivo study (Dalvi and Neal 1978). After intraperitoneal injection of 14C-carbon disulfide in nonpretreated rats, carbonyl sulfide was excreted by the lung in greater quantities than carbon dioxide. Pretreatment with phenobarbital, however, resulted in a greater amount of excretion of carbon dioxide than carbonyl sulfide. In both experiments, excretion of 14C-carbonyl sulfide and carbon dioxide accounted for 14-43% of the total administered radioactivity, with about twice as much carbon dioxide. These results indicate that phenobarbital treatment caused induction of cytochrome P-450 which catalyzed the conversion of carbon disulfide to carbonyl sulfide faster in pretreated rats than in rats not pretreated with phenobarbital. The role of the cytochrome P-450 monooxygenase system in catalyzing carbonyl sulfide formation was also confirmed by in vitro studies (Dalvi et al. 1974, 1975). The rate of carbonyl sulfide formation was NADPH-dependent and increased with microsomes obtained from phenobarbital-treated rats. 

In contrast to the 4-hydroxy isomers, the thermally stable 5-hydroxy-THISs add to the C=C bond of cyclopropenylidenes (4. 18, 27. 28). The adducts eliminate carbonyl sulfide, and the strained bond breaks resulting in ring-expansion with formation of pyridin-4-ones. -thiones, or -imines. or 4-alkylidenedihydropvridines (20, X = 0. S.NR. or CRR ) (Scheme 19). 

Hydroxy-THISs add regioselectively to the C=N bonds of isocyanates or isothiocyanates. The initially formed cycloadducts eliminate carbonyl sulfide with formation of 4-hydroxy- or 4-mercaptoimidazolium hydroxide inner salts (21) (Scheme 21). 4-Hydroxyimidazolium hydroxide... 

Charcoal—sulfur processes need low ash hardwood charcoal, prepared at 400—500°C under controlled conditions. At the carbon disulfide plant site, the charcoal is calcined before use to expel water and residual hydrogen and oxygen compounds. This precalcination step minimises the undesirable formation of hydrogen sulfide and carbonyl sulfide. Although wood charcoal is preferred, other sources of carbon can be used including coal (30,31), lignite chars (32,33), and coke (34). Sulfur specifications are also important low ash content is necessary to minimise fouling of the process equipment. 

Due to the presence of hydrocarbons in the gas feed to the burner section, some undesirable reactions occur, such as the formation of carbon disulfide (CS2) and carbonyl sulfide (COS). A good catalyst has a high activity toward H2S conversion to sulfur and a reconversion of COS and CS2 to sulfur and carbon oxides. Mercaptans in the acid gas feed results in an increase in the air demand. For example, approximately 5-13% increase in the air required is anticipated if about 2 mol% mercaptans are present. The increase in the air requirement is essentially a function of the type of mercaptans present. The oxidation of mercaptans could be represented as ... 

Leman, L., Orgel, L. and Ghadiri, M.R. (2004). Carbonyl sulfide - mediated prebiotic formation of... 

The fate of thiocyanate in soil is largely uncharacterized. Early studies have shown that thiocyanate can undergo both aerobic (Betts et al. 1979) and anaerobic microbial degradation (Betts et al. 1979 Stafford and Callely 1969 Youatt 1954) however, the degradation pathway has not been defined (Brown and Morra 1993). Saturated soils treated with thiocyanate were found to emit carbonyl sulfide (COS) (Minami 1982 Minami and Fukushi 1981). Katayama et al. (1992, 1993) have reported the formation of carbonyl sulfide from the biodegradation of thiocyanate by pure and mixed cultures of Thiobacillus thioparus. 

Katayama Y, Narahara Y, Inoue Y, et al. 1992. A thiocyanate hydrolase of Thiobacillus thioparus. A novel enzyme catalyzing the formation of carbonyl sulfide from thiocyanate. J Biol Chem 267(13) 9170-9175. 

Dimethylbisthiomalonic acid (120), when treated with an acylated enol, produced intermediate 121 thietanediones 122 and 123 then were formed by elimination of thioketone and acetic acid (see Eq. 12). Similarly, cyclobutane-l,l-bisthiolcarboxylic acid gave 123, a previously unknown sulfur analog of malonic anhydride, (Eq. 12). Thermolysis of 120 also results in the formation of the four-membered heterocycles in addition to carbonyl sulfide, hydrogen sulfide, and thiocarbonic acid. ... 

A new interesting development has been offered by Orgel and coworkers (Leman et al., 2004) they showed that carbonyl sulfide (COS), a simple volcanic gas, brings about the formation of peptides from amino acids under mild conditions in aqueous solution, and in yields approaching 80% in minutes to hours at room temperature. Dipeptides and tripeptides were thus obtained, but in this case too the answer to the question of long chains with a regulated order of sequence remains elusive. 

Franz and Black539 have studied the thermolysis and photolysis of l,3,4-oxathiazol-2-one (l).530 This compound is thermally labile and yields benzonitrile and sulfur instead of the expected phenyl isocyanate and carbonyl sulfide. It is probable that benzonitrile sulfide (3) is an intermediate and this appears to be confirmed by formation of the adduct 4 in 90% yield when 1 is heated with 2 moles of DMAD at 130° in chlorobenzene. Heating a mixture of benzonitrile and sulfur with DMAD gave tetramethyl thiophenetetracarboxylate (6), also obtained without the nitrile. The formation of the isomeric isothiazoles 7 and 8 from 1 and EP531 is similar to the production of the corresponding... 

In all amino acid and peptide radiolysis, sulfur dioxide and carbonyl sulfide were found in varying amounts, but at present no explanation for the formation of these compounds can be offered. 

Biogenic Sulfur Emissions from the Ocean. The ocean is a source of many reduced sulfur compounds to the atmosphere. These include dimethylsulfide (DMS) (2.4.51. carbon disulfide (CS2) (28). hydrogen sulfide (H2S) (291. carbonyl sulfide (OCS) (30.311. and methyl mercaptan (CH3SH) ( ). The oxidation of DMS leads to sulfate formation. CS2 and OCS are relatively unreactive in the troposphere and are transported to the stratosphere where they undergo photochemical oxidation (22). Marine H2S and CH3SH probably contribute to sulfate formation over the remote oceans, yet the sea-air transfer of these compounds is only a few percent that of DMS (2). 

Leman LJ, Orgel LE, Ghadiri MR. Carbonyl sulfide-mediated prebiotic formation of peptides. Science 2004 306 283-286. 

Rates of CO and Mercaptan Formation in the 2288 A. Phololysis of Carbonyl Sulfide with Added Ethane and Propane as a Function of Reaction Temperature ... 

---