Chlorobenzene reaction with, phosgene

The first stage in the production of MDI (9d) is condensation between aniline and formaldehyde, in the presence of HC1, under subatmospheric pressure, at 70-105 °C. This affords 4,4, 2,4 and 2,2 isomers of diaminodiphenylmethane (9a, 9b and 9c). Reaction with phosgene in an inert solvent, such as chlorobenzene, first at low temperature, and then heating to 120 °C, gives, for the 4,4 isomer (9a), MDI, trimers, tetramers and higher oligomers, the latter known as poly-MDI or PMDI. Continuous liquid-phase phosgenation is favored. 

Sulphonic acids and their salts are analysed by GC after esterification with diazomethane or after chlorination with thionyl chloride or phosgene [119]. Reaction with thionyl chloride proceeds according to Scheme 5.14. A 0.5-g sample of sulphonic acid or its salt is placed into a round-bottomed flask fitted with a magnetic stirrer and a reflux condenser, 0.5 ml of dimethylformamide and 20 ml of thionyl chloride are added and the mixture is refluxed for several minutes up to 2 h (according to the character of the sample) until the evolution of gas from the reaction mixture ceases (detection with the aid of a bubbler filled with chlorobenzene). If a salt is chlorinated, solid chloride produced in the reaction mixture must be removed by dilution with dichloromethane and by careful filtration through a fine glass filter. Excess of thionyl chloride and solvent is evaporated carefully under decreased pressure. The residue is dissolved in a suitable solvent (CCU) and analysed by GC (silicone stationary phase, temperature 160°C). 

The phosgenation of N,N -dialkyl- and N-alkyl-N -arylureas at 110-120 °C in chlorobenzene, followed by reaction with amines affords N,N, N"-trisubstituted guanidines via the intermediate chloroformamidines. ... 

Cyclizations can occur when two amino groups are adjacent on a benzene ring. For example, reaction of phosgene with 2,3-diaminotoluene in chlorobenzene gave a precipitate containing a five-membered ring, considered to be a cyclic urea [1154] ... 

Reaction of thioureas with phosgene is usually performed at room temperature in an inert solvent (such as benzene, chlorobenzene or 1,2-dichloroethane) in which the thiourea is soluble. By-products, if formed, are readily separated with ethoxyethane in which the chloroformamidinium chloride salts are insoluble. 

The TPPO-containing residues are dissolved in chlorobenzene and reacted with phosgene gas to form triphenylphosphine chloride, with liberation of CO2. In the second step, finely divided aluminum powder is added with mixing. The TPP AICI3 complex formed is then decomposed hydrolytically in a third reaction step, giving the desired TPP. 

Block copolyesters also form in reactions between hydroxy and acid chloride-terminated prepolymers. This can take place in the melt or in solution in such solvents as chlorobenzene or o-dichlorobenzene. For relatively inactive acid chlorides, like terephthaloyl chloride, high reaction temperatures are required. Phosgene also reacts with hydroxy-terminated polyesters to form block copolymers. The reactions must be carried out in an inert solvent. Block copolyethers also form readily by ester interchange reactions with low molecular weight diesters ... 

The reaction of toluenediamine with phosgene can be carried out in solution or in the gas-phase. Less active aromatics with high boiling points, such as o-di-chlorobenzene, are used as solvents. 

Preparation by partial demethylation of 2-hydroxy-2, 4,4 -trimethoxybenzo-phenone or 2,2, 4,4 -tehamethoxybenzophenone with aluminium chloride or aluminium bromide in chlorobenzene at 90-95° (good yield). The same result is obtained using ethylene dichloride or nitrobenzene as the solvent [655], Preparation by reaction of phosgene with resorcinol dimethyl ether in the presence of aluminium chloride [215]. 

At higher temperatures, in an inert solvent such as chlorobenzene,, lV -disubstituted ureas react with COCl to give guanidine derivatives, RNHC(=NR)NHR (R = various alkyl or aryl substituents) [724a], formed from the further reaction of the Vilsmeier salt with an excess of urea. With an excess of phosgene present, -chloroformyl derivatives may be obtained [724a] ... 

When the solvent takes part in acid-base phenomena, the reactions are usually displacement reactions. Considering only acid-base reactions, solvents may be divided into three classes (1) those that are ordinarily inert toward acids and bases, e.g., benzene, carbon tetrachloride, and chlorobenzene (2) those that are ionizable, e.g., water, ammonia, sulfur dioxide, phosgene, and selenium oxychloride (3) those that do not ionize but do react with acids and bases, e.g., ether and pyridine. If we consider the neutralization of boron trichloride by triethylamine in the three types of solvents, we find that the net result may be the same as when the neutralization occurs in the absence of a solvent ... 

---