Aniline hydrogenation

A second preparation to illustrate sulphonation is that of sulphanilic acid, NH2C4H4SO3H, a highly crystalline substance which, having a low solubility in cold water, can be readily isolated. If aniline is treated with an excess of concentrated sulphuric acid, aniline hydrogen sulphate is first formed, and... 

DCHA is normally obtained in low yields as a coproduct of aniline hydrogenation. The proposed mechanism of secondary amine formation in either reductive amination of cyclohexanone or arene hydrogenation iHurninates specific steps (Fig. 1) on which catalyst, solvents, and additives moderating catalyst supports all have effects. 

Contaminant by-products depend upon process routes to the product, so maximum impurity specifications may vary, eg, for CHA produced by aniline hydrogenation versus that made by cyclohexanol amination. Capillary column chromatography has improved resolution and quantitation of contaminants beyond the more fliUy described packed column methods (61) used historically to define specification standards. Wet chemical titrimetry for water by Kad Eisher or amine number by acid titration have changed Httle except for thein automation. Colorimetric methods remain based on APHA standards. 

Alicyclic amines are used as pesticides, plasticizers, explosives, inhibitors of metal corrosion and sweetening agents as well as having uses in the pharmaceuticals industry. Aniline hydrogenation has been studied in the literature with the main reaction products cyclohexylamine, dicyclohexylamine, A-phenylcyclohexylamine, diphenylamine, ammonia, benzene, cyclohexane, cyclohexanol and cyclohexanone [1-9], The products formed depend on the catalyst used, reaction temperature, solvent and whether the reaction is performed in gas or liquid phase. For example high temperature, gas-phase aniline hydrogenation over Rh/Al203 produced cyclohexylamine and dicyclohexylamine as the main products [1],... 

Partridge, S.M., Aniline hydrogen phthalate as a spraying reagent for chromatography of sugars, Nature, 164, 443, 1949. 

Aniline hydrogen phthalate Variety of colors (limit 1 pg) 116... 

Gas/ Bulk chemicals (Air Aniline Hydrogenation of Replacement of Retrofitting in No catalyst/ (37,144-146)... 

The protein polysaccharide is hydrolyzed at 100-110° for 3 hours with N sulfuric acid, neutralized with baryta solution, filtered, and the filtrate concentrated to small volume. Zone electrophoresis in borate buffer (pH 8.6) is then carried out for a suitable time, and the paper strip is dried and sprayed with ninhydrin (to locate the amino acids) and with aniline hydrogen phthalate (to detect the reducing sugars). 

The relative positions of the amino acids and sugars may give useful information. Alternatively, the paper may be subjected to chromatography in a direction at right angles to that of the zone electrophoretic separation in which case, the paper should finally be sprayed rs< with aniline hydrogen phthalate and then with ninhydrin. 

The coupling reaction in aniline hydrogenation generally is decreased by addition of ammonia, but Rh is poisoned by ammonia. 

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