Alcohols phosgene

The reagent is generated in toluene solution at—60 from furfuryl alcohol, phosgene, and triethylamine. ... 

CaHjNCO, PhNCO. A pungent lachrymatory almost colourless liquid m.p. — 33 "C, b.p. 162°C. Used as a dehydrating agent and for characterization of alcohols. Prepared from aniline and phosgene in the presence of hydrogen chloride. 

Pure chloroform has b.p. 61°/760 mm. The solvent, when free from alcohol, should be kept in the dark in order to avoid the photochemical formation of phosgene. It must not be dried with sodium as an explosion may occur. 

Chloroform undergoes oxidation to the very poisonous phosgene upon exposure to light and air. Commercial specimens are therefore stored in brown bottles and contain 1-2 per cent, of alcohol the latter converts the toxic phosgene into the harmless substance diethyl carbonate ... 

Reductive carbonylation of nitro compounds is catalyzed by various Pd catalysts. Phenyl isocyanate (93) is produced by the PdCl2-catalyzed reductive carbonylation (deoxygenation) of nitrobenzene with CO, probably via nitrene formation. Extensive studies have been carried out to develop the phosgene-free commercial process for phenyl isocyanate production from nitroben-zene[76]. Effects of various additives such as phenanthroline have been stu-died[77-79]. The co-catalysts of montmorillonite-bipyridylpalladium acetate and Ru3(CO) 2 are used for the reductive carbonylation oLnitroarenes[80,81]. Extensive studies on the reaction in alcohol to form the A -phenylurethane 94 have also been carried out[82-87]. Reaction of nitrobenzene with CO in the presence of aniline affords diphenylurea (95)[88]. 

Phosgene (165) or thionyl chloride in the presence of an acid catalyst (166) gives good yields of 4-chlorobutyryl chloride. Heating butyrolactone and thionyl chloride in an alcohol gives good yields of 4-chlorobutyric esters (167). 

Rea.ctlons, As with other tertiary alcohols, esterification with carboxyUc acids is difficult and esters are prepared with anhydrides (181), acid chlorides (182), or ketene (183). Carbamic esters may be prepared by treatment with an isocyanate (184) or with phosgene followed by ammonia or an amine (185). 

Attempts have been made to develop methods for the production of aromatic isocyanates without the use of phosgene. None of these processes is currently in commercial use. Processes based on the reaction of carbon monoxide with aromatic nitro compounds have been examined extensively (23,27,76). The reductive carbonylation of 2,4-dinitrotoluene [121 -14-2] to toluene 2,4-diaLkylcarbamates is reported to occur in high yield at reaction temperatures of 140—180°C under 6900 kPa (1000 psi) of carbon monoxide. The resultant carbamate product distribution is noted to be a strong function of the alcohol used. Mitsui-Toatsu and Arco have disclosed a two-step reductive carbonylation process based on a cost effective selenium catalyst (22,23). 

The reaction of phosgene with alcohols yields chloroformates, and with a basic catalyst present, carbonates ate formed ... 

DADC Monomers. Reaction of aHyl alcohol in the presence of alkaU with diethylene glycol bis(chloroformate), obtained from the glycol and phosgene, gives the monomer... 

In another method, phosgene is gradually passed into 1,2-propylene glycol (9). The chloroformate is washed, dried, and distilled at 266 Pa (2 mm Hg) and added slowly to a mixture of aHyl alcohol and pyridine below 15°C. The purified monomer 1,2-propylene glycol bis(aHyl carbonate) (C H O ) heated with lauroyl peroxide at 70°C gives a hard clear, polymer. 

The reaction of phosgene (carbonic dichloride [75-44-5]) with alcohols gives two classes of compounds, carbonic esters and carbonochloridic esters, commonly referred to as carbonates and chloroformates. The carbonic acid esters (carbonates), R0C(0)0R, are the diesters of carbonic acid [463-79-6]. The carbonochloridic esters, also referred to as chloroformates or chlorocarbonates, C1C(0)0R, are esters of hypothetical chloroformic acid [463-73-0] CICOOH. 

Unreacted phosgene is removed from the cmde chloroformates by vacuum stripping or gas purging. Chloroformates of lower primary alcohols are distillable however, heavy-metal contamination should be avoided. As stated earlier, chloroformates generating a stable carbonium ion on decomposition, ie, secondary or tertiary chloroformates or henzylic chloroformates, are especially unstable in the presence of heavy metals and more specifically Lewis acids and, hence, should be distilled at as low a temperature and high vacuum as possible. 

Carbonates ate manufactured by essentially the same method as chloroformates except that more alcohol is required in addition to longer reaction times and higher temperatures. The products are neutralized, washed, and distilled. Corrosion-resistant equipment similar to that described for the manufacture of chloroformates is requited. Diaryl carbonates are prepared from phosgene and two equivalents of the sodium phenolates or with phenols and various... 

Liquid aliphatic halides are obtained alcohol-free by distillation from phosphorus pentoxide. They are stored in dark bottles to prevent oxidation and, in some cases, the formation of phosgene. 

Typically in such a process the bis-phenol A is dissolved in about ten times its weight of pyridine and vigorously stirred at 25-35°C. Phosgene is then bubbled into the solution and in a few minutes the pyridine hydrochloride starts to precipitate. As polymer is formed the viscosity of the solution increases and eventually becomes too great for stirring. The polymer is then recovered by the addition of a solvent such as methyl alcohol which dissolves the pyridine hydrochloride but precipitates the polymer. 

In one projected commercial modification of the process the phosgenation stage is replaced by one in which the nitro compounds are reacted with CO and an alcohol to form a urethane. This is then split to form an isocyanate in the second step. 

For environmental reasons there has been interest in methods for manufacturing isocyanates without the use of phosgene. One approach has been to produee diurethanes from diamines and then to thermal eleave the diurethanes into diisocyanates and alcohols. Although this method has been used for the production of aliphatic diisocyanates such as hexamethylene diisocyanate and isophorone diisocyanate, for economic reasons it has not been adopted for the major aromatic isocyanates MDI and TDI. 

Properties.—Colourless liquid possessing a sweet smell, b. p. 60—62° sp.gr. 1-498 at 15° very slightly soluble in water non-inflammable. As chloroform slowly decomposes in presence of air and sunlight into phosgene, it is usual to add a little alcohol to the commcicial product, which arrests the change. Pure chloroform is neutral to litmus, has no action on silver nitrate solution and does not discolour concentrated sulphuric acid when shaken with it for an hour or left for a day. 

Dihydro-2-hydroxyquinazolines have been prepared by cyclizing o-ureidobenzyl alcohols with hydrochloric acid and can be prepared less conveniently from o-aminobenzylamines and phosgene (see 3a). 

About 3 grams of 0-methylcholine chloride are stirred at room temperature with an excess of phosgene dissolved in 50 grams of chloroform, for about 2 hours. Excess phosgene and hydrochloric acid are removed by distillation under vacuo. Additional chloroform is added to the Syrup and the mixture is poured into excess ammonia dissolved in chloroform and cooled in solid carbon dioxide-acetone. The solid is filtered and extracted with hot absolute alcohol. The solid in the alcohol is precipitated with ether, filtered, and recrystallized from isopropanol. The carbaminoyl-0-methylcholine chloride obtained has a melting point of about 220°C. 

In the formation of tert-butyl azidoformate by the addition of phosgene to alcohols followed by the addition of Na nitride or hydrazoic acid in the presence of pyridine, reaction of phosgene with the azide can cause the formation of expl carbazide (Ref 9)... 

The reaction between isopropyl alcohol and phosgene forms isopropyl chloroformate and HC1. In the presence of Fe salts thermal de compn can occur, which in some cases can become expl (Ref 7)... 

An important example is the preparation of carbobenzoxy chloride (PhCH20C0Cl) from phosgene and benzyl alcohol. This compound is widely used for protection of amino groups during peptide synthesis (see 10-55). 

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