Thiophosgene

2CS2 + 5Cl2- 2CSCI4 + S2CI2 2S2Cl2 t 2H20 — SO2 t 3  

Preparation of Thiocarbonyl Per chloride.—In a 5-I. bottle arranged for cooling by running water is placed 500 g. (6.58 moles) of dry carbon disulfide (Note i) to which 0.5 g. of iodine has been added. Dry chlorine is passed into the cooled carbon disulfide at such a rate that the temperature does not rise above 25°, until the liquid weighs 1770 g. (17.9 moles chlorine) (Note 2). The time required is about forty hours. The product is a deep red liquid, a mixture of impure thiocarbonyl perchloride and sulfur chloride. 

The apparatus illustrated in Fig. 3 is assembled, in a large hood if possible (Note 3). A is a 5- . round-bottom flask heated by a large ring burner and provided with a specially treated four-hole cork stopper covered with tin foil (Note 4). To these holes are fitted the column Z), the tube B reaching to the bottom of A, the specially bent tube C reaching up the inside of D, and the tube K connected with the tubes leading to the 2-I. separatory funnel H, so that the distance between the stopper of A and the stopcock of H is at least 100 cm. The bottom of the column D is of 20 mm. bore while the main portion is 30 mm. The side arm should be at least 85 cm. above the stopper of 4. The tube C 

H is placed at the highest available level (Note 5) and connected with the tubes 7, 7, and K in such a manner as to secure a pressure of liquid sufficient to more than balance the steam pressure (Note 6). E and F are specially constructed condensers of unusual length (160 cm. and 85 cm., respectively) and bore (40 mm.) made from large glass tubing and rubber stoppers (Note 7). I he top of condenser E is connected to a good draft chamber. 

The crude, dry thiocarbonyl perchloride is distilled through an efficient 60-cm. column (Note 9). The distillate below 140 is discarded. The fraction boiling at 140-155 at atmospheric pressure amounts to about 600 g. The boiling point of pure thiocarbonyl perchloride is 149°. 

Photodissociation dynamics of this molecule were studied using the TOF technique to determine the velocity distribution of the fragments when the molecule is photolyzed with a KrF laser at 248 nm (182). Absorption at this wavelength leads to the excitation of the second singlet state, the B- -Ai state, from the X A ground state. From the TOF spectra of the CS fragment they were able to show that both of the following reactions occur  

They estimate that the quantum yield of reaction 61 if 0.8 while that of reaction 62 is C.2. The fraction of available energy 

This last reaction also takes place with some other reducing agents, such as copper and silver powder. 

When treated in the cold with chlorine, perchloromethyl mercaptan is converted into sulphur chloride and carbon tetrachloride  

In contact with iron, perchloromethyl mercaptan decomposes even at ordinary temperatures.  

Perchloromethyl mercaptan has an irritant action on the eyes. The minimum concentration capable of causing this irritation is 10 mgm. per cu. m. of air. The limit of insupportability is 70 mgm. per cu. m. and the mortality-product is 3,000 (Muller). 

It may be obtained by passing a mixture of carbon tetrachloride and hydrogen sulphide through a red-hot tube, or by passing perchloromethyl mercaptan over silver powder  

---

Ketene Insertions. Ketenes insert into strongly polarized or polarizable single bonds, such as reactive carbon—halogen bonds, giving acid hahdes (7) and into active acid haUdes giving haUdes of p-ketoacids (8) (46). Phosgene [77-44-5] (47) and thiophosgene [463-71-8] (48) also react with ketenes. 

Physical Properties. Thiophosgene [463-71-8] (thiocarbonyl chloride), CSCI2, is a malodorous, red-yeUow Hquid (bp 73.5°C, ( 20 1.5442). It is only slightly soluble with decomposition in water, but it is soluble in ether and various organic solvents. 

Thiophosgene reacts with alcohols and phenols to form chlorothionoformates or thiocarbonates. The most studied reactions of thiophosgene are with primary amines to give isothiocyanates and with secondary amines to give thiocarbamyl chlorides ... 

The reaction of thiophosgene with various bisphenols using phase-transfer catalysis gives polythiocarbonates (44) ... 

Most of the reactions of thiophosgene involve the expected chemistry of an acid chloride, in which the chlorine atoms are replaceable by various nucleophiles. A reaction involving the C=S bond is the Diels-Alder addition ... 

Preparation. Thiophosgene forms from the reaction of carbon tetrachloride with hydrogen sulfide, sulfur, or various sulfides at elevated temperatures. Of more preparative value is the reduction of trichi oromethanesulfenyl chloride [594-42-3] by various reducing agents, eg, tin and hydrochloric acid, staimous chloride, iron and acetic acid, phosphoms, copper, sulfur dioxide with iodine catalyst, or hydrogen sulfide over charcoal or sihca gel catalyst (42,43). 

There is no fiiU-scale U.S. commercial production of thiophosgene, but it is available in glass ampuls from laboratory reagent suppHers. Thiophosgene may be produced in Israel as an intermediate for tolnaftate (2-naphthyl A/-methyl-A/-y -tolylthiocarbamate) [2398-96-17, an antifimgal dmg. 

The MSDS (46) for thiophosgene describes it as highly toxic, corrosive lachrymator and moisture sensitive compound. It may be fatal if inhaled, swallowed, or absorbed through the skin. When using this material one should wear the appropriate NIOSH/OSHA-approved respirator, chemical-resistant gloves, safety goggles, and other protective clothing. It should be used only in a chemical fume hood. 

Tiichloiomethanesulfenyl chloiide can be reduced to thiophosgene by metals in the presence of acid and by various other reducing agents. The sulfur-bonded chlorine of trichloromethanesulfenyl chloride is most easily displaced by nucleophilic reagents, but under some conditions, the carbon-bound chlorines are also reactive (54). 

Thiophosgene, MSDS, No. T9136, Aldrich Chemical Co., Milwaukee, Wis., May 11, 1995. 

If bromine is used in equation 8, carbon tetrabromide [558-13-4] is formed. With a minor amount of iodine present, and in the absence of iron catalyst, carbon disulfide and chlorine react to form trichioromethanesulfenyl chloride (perchloromethyl mercaptan [594-42-3]), CCI3SCI, which can be reduced with staimous chloride or tin, and hydrochloric acid to form thiophosgene (thiocarbonyl chloride [463-71-8], CSCI2, an intermediate in the synthesis of many organic compounds (see Sulfurcompounds). 

A similar utilization of two heteroatoms is illustrated by the reaction of the ethylenedithiol (120) with formic acid in the presence of perchloric acid. 4,5-Diphenyl-l,3-dithiolylium perchlorate (121) was formed in 45% yield (69MI40300). Introduction of a 2-oxo or 2-thioxo substituent as in (123 X = 0, S) is illustrated by the reaction of the disodium salt (122) with phosgene and thiophosgene, respectively (76S489). 

Because of the objectionable properties of thiophosgene, care should be exercised in its use. 

Chlorophenyl isothiocyanate has also been prepared by treating an alcoholic solution of sym-di-/)-chlorophenyl thiourea with iodine/ from ammonium -chloroplienyldithiocarbamate and lead nitrate/ (p. 72), and from the action of thiophosgene with /)-chloroaniline. ... 

The crude thiophosgene is separated and dried with about 10 g. of calcium chloride, and fractionated with a good column. Very little distils below 73°. The fraction boiling at 73-76° at atmospheric pressure is pure thiophosgene and amounts to about... 

Thiophosgene has been prepared in small yield by the chlorination of carbon disulfide in the presence of iodine and by the reduction of thiocarbonyl perchloride. ... 

Thionyl chloride Thiophosgene Titanium tetrachloride Trichloromethyl perchlorate Triformoxime trinitrate Trimethylacetyl chloride Trimethylene glycol diperchlorate Trimethylol nitromethane trinitrate... 

The related thionocarbonate is prepared from thiophosgene (Pyr, DMAP, 78% yield). 

---