Toluene reaction with, phosgene

Two other derivatives of toluene are the important explosive trinitrotoluene (TNT) and the polyurethane monomer toluene diisocyanate (TDI). TNT requires complete nitration of toluene. TDI is derived from a mixture of dinitrotoluenes (usually 80% o,p and 20% o,o) by reduction to the diamine and reaction with phosgene to the diisocyanate. TDI is made into flexible foam polyurethanes for cushioning in furniture (35%), transportation (25%), carpet underlay (20%), and bedding (10%). A small amount is used in polyurethane coatings, rigid foams, and elastomers. 

Toluene diisocyanale is widely used in the manufacture of urethane plastics, particularly the urethane foamed plastics. Another isocyanate, diphenylmethane 4,4 -diisocyanaie, is produced by reaction of aniline and formaldehyde, followed by reaction with phosgene hcho coo.. 

Toluene diisocyanate is derived from a mixture of dinitrotoluenes (usually 65 to 85% o./9-dinitrotoluene and 35 to 15% o,o-dinitrotoluene) followed by reduction to the diamine and reaction with phosgene to the diisocyanate. 

Polyanhydrides of terephthalic acid (10.39), isophthalic acid (10.40), and sebacic acid (10.41), were prepared by reaction with phosgene in toluene in the presence of NEtj [1865]. The polymers all have the general structure 10.42 X = l,4-CgH4, 1,3-CgH or (CHj). ... 

It is particularly important to remove 2,3- and 3,4-toluenediamine by distillation since, in the subsequent reaction with phosgene, these compounds would produce benzimidazolones which, having active amide hydrogen atoms, can react with the principal product, toluene diisocyanate, and reduce the yield. 

Diisocyanates are commonly used with either diols or a mixture of diols and polyols. When diols are exclusively used and the trimerization reaction is minimized, the polyurethane is substantially linear, but it becomes increasingly three-dimensional with increasing levels of polyol or with trimerization of the diisocyanate. The trimerization reaction and the use of polyols enable thermoset polyurethanes. Common diisocyanates include toluene diisocyanate (TDl), methylene diphenyl diisocyanate (MDl), naphthalene diisocyanate (NDl), and hexamethylene diisocyanate (HDl). TDI is prepared by the nitration of toluene to give a mixture of mainly 2,4- and 2,6-dinitrotoluene, followed by reduction and reaction with phosgene. The isomers are typically not separated and are used as a mixture. 

Naphthol is mainly used in the manufacture of the insecticide carbaryl (59), l-naphthyl A/-methyicarbamate/ iJ-2j5 - (Sevin) (22), which is produced by the reaction of 1-naphthol with methyl isocyanate. Methyl isocyanate is usually prepared by treating methylamine with phosgene. Methyl isocyanate is a very toxic Hquid, boiling at 38°C, and should not be stored for long periods of time (Bhopal accident, India). India has developed a process for the preparation of aryl esters of A/-alkyl carbamic acids. Thus l-naphthyl methylcarbamate is prepared by refluxing 1-naphthol with ethyl methylcarbamate and POCl in toluene (60). In 1992, carbaryl production totaled > 11.4 x 10 t(35). Rhc ne-Poulenc, at its Institute, W. Va., facihty is the only carbaryl producer in United States. 

Phosgenation. The most important reaction of y -toluenediamine is with phosgene [75-44-5] to give toluene diisocyanate TDI (see... 

Toluene Diisocyanate. Toluene diisocyanate is the basic raw material for production of flexible polyurethane foams. It is produced by the reaction sequence shown below, in which toluene is dinitrated, the dinitrotoluene is hydrogenated to yield 2,4-diaminotoluene, and this diamine in turn is treated with phosgene to yield toluene 2,4-diisocyanate. 

However, the reaction with R8eCl (R=4-C1C6H4) gives a mixture of (R8e)28 (n=l-7) and R28e2 [125]. Heating of this mixture results in the formation of a more complicated mixture, (R8e)28 ( =0-10), instead of the convergence to a thermodynamically stable compound. When a toluene solution of phosgene is added to a solution of (TiCp 2)2(p-S2)2 in C82, the acyclic trisulfido complex (TiCp 2Cl)2(p-83) is obtained in 18% yield [130]. 

The reagent is prepared1 by reaction of phosgene with 3,5-dioxo-4-methyl-l,2,4-oxadiazolidine in refluxing toluene (82% yield). It serves as a coupling reagent for esterification and preparation of amides and carbamates. 

The two key isocyanates that are used in the greatest volumes for polyurethane polymers are toluene diisocyanate (TDl) and methylene diphenyl diisocyanate (MDl). Both isocyanates are produced first by nitration of aromatics (toluene and benzene, respectively), followed by hydrogenation of the nitro aromatics to provide aromatic amines. In the case of MDl, the aniline intermediate is then condensed with formaldehyde to produce methylene dianiline (MDA), which is a mixture of monomeric MDA and an oligomeric form that is typical of aniline/formaldehyde condensation products [2]. The subsequent reaction of phosgene with the aromatic amines provides the isocyanate products. Isocyanates can also be prepared by the reaction of aromatic amines with dimethylcarbonate [3, 4]. This technology has been tested at the industrial pilot scale, but is not believed to be practiced commercially at this time. 

The reagent is obtained (90% yield) by reaction of 2-hydroxypyridine with phosgene and N(C2H5)3 in CH2C12/toluene.1... 

The production of isocyanates is based on the reaction of phosgene with primary amines. Toluene di-isocyanate is the most frequently used di-isocyanate. 

---