Phosgene hydrolysis

Preparation of Arylcarboxylic Acids and Derivatives. The general Friedel-Crafts acylation principle can be successfully appHed to the preparation of aromatic carboxyUc acids. Carbonyl haUdes (phosgene, carbonyl chloride fluoride, or carbonyl fluoride) [353-50-4] are diacyl haUdes of carbonic acid. Phosgene [75-44-5] or oxalyl chloride [79-37-8] react with aromatic hydrocarbons to give aroyl chlorides that yield acids on hydrolysis (133) ... 

Reportedly, simple alkyl isocyanates do not dimerize upon standing. They trimerize to isocyanurates under comparable reaction conditions (57). Aliphatic isocyanate dimers can, however, be synthesized via the phosgenation of A[,A[-disubstituted ureas to yield /V-(ch1orocarhony1)ch1oroformamidine iatermediates which are subsequendy converted by partial hydrolysis and base catalyzed cycUzation. This is also the method of choice for the synthesis of l-alkyl-3-aryl-l,3-diazetidiones (mixed dimers of aromatic and aUphatic isocyanates) (58). 

Phosgene addition is continued until all the phenoHc groups are converted to carbonate functionahties. Some hydrolysis of phosgene to sodium carbonate occurs incidentally. When the reaction is complete, the methylene chloride solution of polymer is washed first with acid to remove residual base and amine, then with water. To complete the process, the aqueous sodium chloride stream can be reclaimed in a chlor-alkah plant, ultimately regenerating phosgene. Many variations of this polycarbonate process have been patented, including use of many different types of catalysts, continuous or semicontinuous processes, methods which rely on formation of bischloroformate oligomers followed by polycondensation, etc. 

Its production was 621 t and the average price 0.75/kg in 1987. Direct YeUow 44 (64) is prepared by phosgenation of an equimolar mixture of metanilic acid coupled to o-anisidinomethanesulfonic acid (with subsequent hydrolysis of the methanesulfonic acid group) and nitro aniline coupled to sahcychc acid (with subsequent reduction of the nitro group). 

Stabilized tetrachloroethylene, as provided commercially, can be used in the presence of air, water, and light, in contact with common materials of constmction, at temperatures up to about 140°C. It resists hydrolysis at temperatures up to 150°C (2). However, the unstabilized compound, in the presence of water for prolonged periods, slowly hydrolyzes to yield trichloroacetic acid [76-03-9] and hydrochloric acid. In the absence of catalysts, air, or moisture, tetrachloroethylene is stable to about 500°C. Although it does not have a flash point or form flammable mixtures in air or oxygen, thermal decomposition results in the formation of hydrogen chloride and phosgene [75-44-5] (3). 

Benzophenone has been prepared by the distillation of calcium benzoate,1 by the action of benzoyl chloride on benzene in the presence of aluminium chloride,2 by the action of phosgene on benzene in the presence of aluminium chloride,3 by the action of carbon tetrachloride on benzene in the presence of aluminium chloride followed by hydrolysis.4... 

In the alkyl chain hydroxy groups or side chains may be present. The reaction is somewhat different when acyl halides are used. Hydroxymethanediphosphonic acid is prepared by reacting phosgene with an alkali metal, dialkyl phosphite. The reaction is rapid and exothermic. The temperature is controlled between 10 and 20°C. After hydrolysis with HC1, hydroxymethanediphosphonic acid is recovered [91,92]. 

Synthetic routes that access appropriately substituted thienobenzazepines are also quite important for medicinal chemistry stracture activity relationship studies, and many involve similar bond connectivity strategies. One notable example employs the use of conunercially available 4-methyl-3-nitrophenol (Scheme 6.3). Methylation of the phenol followed by bromination, hydrolysis, and oxidation of the benzylic alcohol afforded aldehyde 9 in quantitative yield. Treatment of this aldehyde with 5-lithio-2-methylthiophene provided, after dehydroxylation, nitro intermediate A in good overall yield. Reduction of the nitro functionality and treatment with phosgene presented the corresponding isocyanide which upon cychzation using aluminum trichloride in a Friedel-Crafts fashion afforded the... 

AyV -Carbonyl-2,2 -biimidazole (A V7-carbonyl-2,2 -biimidazyl) prepared from 2,2 -biimidazole and phosgene is relatively unreactive on hydrolysis, and shows reduced reactivity in reactions with carboxylic acids.[19],[2]... 

In an attempt to form orally active penicillins unrelated to ampicillin, use was made of the fact that certain spiro a-aminoacids, such as 9, are well absorbed orally and transported like normal amino acids. Reaction of cyclohexanone with ammonium carbonate and KCN under the conditions of the Bucherer-Bergs reaction led to hydantoin 10. On acid hydrolysis, a-amino acid 11 resulted. Treatment with phosgene... 

Triphenylcarbinol has been obtained by the reaction between phenylmagnesium bromide and benzophenone,1 methyl benzoate, or phosgene 8 by action of phenylsodium upon benzophenone, benzoyl chloride, ethyl chlorocarbonate, or ethyl benzoate 4 by hydrolysis of triphenylchloromethane 5 and by oxidation of tri-phenylmethane.6... 

The hydrogen chloride formed by the hydrolysis of phosgene causes initial irritation to the eyes, nasopharynx, and respiratory tract. However, because of phosgene s poor water solubility, a minimal amount of hydrogen chloride is formed (TEMIS 1997). 

Chemical/Physical. Emits toxic phosgene fumes when heated to decomposition (Sax and Lewis, 1987). In a 0.50 N sodium hydroxide solution at 20 °C, chlorpropham hydrolyzed to aniline derivatives. The half-life of this reaction was 3.5 d (El-Dib and Aly, 1976). Simple hydrolysis leads to the formation of 3-chlorophenylcarbamic acid and 2-propanol. The acid is very unstable and is spontaneously converted to 3-chloroaniline and carbon dioxide (Still and Herrett, 1976). 

N,N-Dimethylisobutyramide (Gavrilov, N. Koperina, A. Klutcharova, M. Hull., soc. Chim. France 1945, 12, 773) was converted to l-chloro-N,N,2-11 imrUiylproponylaraine according to the procedure of Org. Synth. 1979, 55, 26, In nl% yield, bp 118-121 C. Freshly-distilled oxalyl chloride was used iir.iKiid of phosgene. The propenylamine should be handled carefully in a vytltii i 1.0 avoid its rapid hydrolysis by moisture. 

A number of hydrolysis products of chloroaluminafe salfs have been defecfed using FAB MS. The problem here is that under some circumstances FAB MS can provide only a restricted view on the surface of fhe sample that is more likely to be oxidized or hydrolyzed rather than the average sample [13]. Nevertheless, this problem is not directly related to MS itself, but rather to a problem of proper sample preparation. Inert conditions during sample preparation and construction of special sample inlet chambers for MS can help avoid fhese reacfions. The addition of phosgene was suggested to reduce problems encountered with such side reactions [22], but here the problems encountered in working with an extremely toxic chemical have to be taken into account. 

Methanol (100 mL), which hydrolyzes unwanted chloroformate compounds in addition to unreacted phosgene, was then added dropwise over 30 min (very slowly at the beginning by pipette). Furthermore, vigorous stirring during methanol addition is required to ensure HCl does not accumulate in the flask, hence preventing the hydrolysis of the ketal to the undesired alcohol. 

Chemical Properties. Thiophosgene is more resistant to hydrolysis than its oxygen analogue, phosgene, but it is slowly hydrolyzed to carbon dioxide, hydrogen sulfide, and hydrochloric acid. It can be oxidized to a lacrimatory thiophosgene 5-oxide (41). Its utility in organic synthesis has been... 

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