Phenylurethanation

A -n-Butylurethane N- ec.-Butylurethane N-Phenylurethane (Ethyl -phenyl carbamate) Ethyl oxanilate... 

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]. 

Phenylsemicarbazide has been obtained by the action of hydrazine hydrate on diphenylurea, phenylurethane,i phenyl isocyanate, or the potassium salt of dibenzohydroxamic acid. For its preparation, Curtius method of treating phenylurea with hydrazine liydratc is better Ilian either the older method of... 

In order that there might be no doubt as to the identity of the synthetical product, it was converted into the nitrosochloride, C,oH, 0, NOCl (melting-point 122°), and phenylurethane, Cj Hj-O. CO. NH. C H (melting-point 113°), and these were compared with specimens made from ordinary terpineol, with the result that the preparations obtained from the two sources were found to be absolutely identical. 

If myrcene be heated with glacial acetic acid to 40° for three to four hours, with the addition of a little sulphuric acid, hydration takes place, and an alcohol, which is termed myrcenol is formed. This body is an oil, of specific gravity 0 9032, refractive index 1 4806 at 15°, and boiling-point 99° at 10 mm. pressure. It yields a phenylurethane melting at 68°. 

The tetrabromide and the phenylurethane of isogeraniol have so far only been obtained in the oily condition. 

It forms a phenylurethane which appears to consist of two isomers melting at 82° to 84° and at 94° to 95° respectively. The formation of these two phenylurethanes makes it probable that pinocarveol is itself a mixture of two isomeric compounds. On oxidation with chromic acid pinocarveol yields a compound CjqHj40 which forms two semi-carbazones,. melting at 210° and 320° respectively. 

Dihydrocarveol yields a phenylurethane, CgHjNH. CO. OCjqHj, melting at- 87° for the optically active variety, and 93° for the optically inactive form. 

Fenchyl alcohol yields a phenylurethane melting at 88° when prepared from the optically inactive alcohol, and at 82-5° when prepared from the optically active form. It yields fenchone on oxidation, which can be identified by its crystalline combinations (vide fenchone). 

It forms a characteristic benzoic ester, Cj HjgO. CO. CgH, melting at 54°. This is a useful compound for identifying menthol and may be obtained by heating menthol with the theoretical amount of benzoic acid, in a sealed tube to 170° excess of acid is removed by shaking with a boiling solution of sodium carbonate, and the ester is crystallised from alcohol. Menthol forms a phenylurethane, melting at 111° to 112°. 

It yields a phenylurethane if it is heated almost to boiliog-point with phenyl-isocyanate. This compound melts, at 106° to 107°. On dehydration with phosphoric acid it yields the sesquiterpene cedrene. The relationship between cedrene and cedrol is probably as follows —... 

A sesquiterpene alcohol, CjgHjgO, has been extracted by means of phthalic anhydride from oil of opoponax resin. It distils at 135° to 137° in vactu) (2 imm.), and yields a crystalline phenylurethane. But as, in spite of repeated crystallisations, it could not be obtained of constant melting-point, it is probable that the substance is a mixture of two or more alcohols. 

It yields a phenylurethane melting at 41°, a semi-carbazone melting at 219° to 220°, and an oxime melting at 125°. The OH group appears to possess alcoholic as well as phenolic functions, forming acetic and benzoic esters, as well as direct combinations with alkalis. 

It combines with chloral to form a compound melting at 131° to 134°. Its phenylurethane melts at 107°. It forms a nitroso-conipound melting at 160° to 162°, when treated with nitrous acid. 

The final residue from the mother liquor is an oil which does not solidify in a freezing mixture, and appears to be a mixture of p- and w-tolylcarbinols. Only a trace of phthalic acid (phenolphthalein test) was obtained by oxidizing this oil with permanganate the portion of it which was more readily soluble in water yielded a phenylurethan which depressed the melting point of the phenylurethan of either />-tolylcarbinol or benzyl alcohol. 

Suitable reagents for derivatizing specific functional groups are summarized in Table 8.21. Many of the reactions and reagents are the familiar ones used in qualitative analysis for the characterization of organic compounds by physical means. Alcohols are converted to esters by reaction with an acid chloride in the presence of a base catalyst (e.g., pyridine, tertiary amine, etc). If the alcohol is to be recovered after the separation, then a derivative which is fairly easy to hydrolyze, such as p-nltrophenylcarbonate, is convenient. If the sample contains labile groups, phenylurethane derivatives can be prepared under very mild reaction conditions. Alcohols in aqueous solution can be derivatized with 3,5-dinitrobenzoyl chloride. 

The two-step process of epitaxial polymerization has been applied to symmetrically substituted diacetylenes First, the monomers have been crystallized epitaxially on alkali halides substrates from solution and the vapor phase. The oriented monomer crystals are then polymerized under the substrate s influence by gamma-irradiation. The diacetylenes in this study are 2,4-hexadiyn-l,6-diol (HD) and the bis-phenylurethane of 5,7-dodecadiyn-l,12-diol (TCDU). The polydiacetylene crystal structures and morphologies have been examined with the electron microscope. Reactivity and polymorphism are found to be controlled by the substrate. 

Phenylurethane.—Another portion is poured into alcohol and the solution is evaporated to dryness. 

The portion of azide which was not used for conversion to cyanate (about 2 g.) is boiled for half an hour under reflux condenser with 5 c.c. of absolute alcohol.1 On concentrating the solution, phenylurethane likewise separates. Melting point 52°. 

The phenylurethane which has been obtained is mixed with three times its weight of slaked lime and cautiously distilled from a small retort. The aniline which passes over can, with a little skill, be redistilled from a small flask, but in any case it should be identified by conversion into acetanilide and by the bleaching powder reaction. 

Figure 5. Contact angle 6 of phenylurethanated Visking film as a function of hydrolysis time (O) receding (9) advancing (-------) unreacted film...

Figure 6. Amount of aniline liberated on hydrolysis of phenylurethanated Vis-...

Figure 7. Surface concentration (Cs) of the hydroxyl groups phenylurethanated with and without tin octoate for cellulose films (O) Visking without catalyst (0) cellophane with tin octoate...

It is also seen that when phenylurethanation is carried out at 30°C with the use of tin octoate as catalyst, the reaction proceeds with a higher rate than that without catalyst in spite of lower temperature, but the products show a similar saturated level of urethanation. 

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