The selenazole crystallizes in colorless long needles, melting at 117.5°C. (corr.) Fromm and Martin[(58)] gave the melting point as 117°C. It is insoluble in water, and in the following solvents it is lightly soluble in the cold, more easily hot: ether, methyl alcohol, acetone, acetic acid, acetic anhydride, chloroform, and nitrobenzene. It is difficultly soluble in ethyl alcohol, ethyl acetate, and carbon tetrachloride, in the cold, but easily soluble hot.
Mononitro Derivative
The mononitro derivative of the selenazole, 6-nitro-2-phenylbenzoselenazole, was prepared by nitration with nitric acid at a low temperature:
Twenty-five grams of the selenazole were dissolved in 150 grams of concentrated sulphuric acid, keeping the temperature below the room temperature until complete solution took place. It was then cooled on a freezing mixture and a mixture of sulphuric and nitric acids (previously prepared and cooled by mixing 9.5 grams of nitric and fifteen grams of sulphuric acids) slowly dropped into it in the course of half an hour, using mechanical stirring for four hours. The solution was then poured into two liters of water (ice water), filtered, dried, and recrystallized from acetic acid, and alcohol with the help of animal charcoal. The yield was 95 per cent.
This nitro compound crystallizes in flattened needles of a light yellow color. It melts at 202.4°C. (corr.). It is very insoluble in water; but soluble in hot acetic acid, acetic anhydride, nitrobenzene, nitrotoluene, toluene, benzene, alcohol, and difficultly soluble when cold. The crystals were analyzed and gave the following results,
| Calculated for C13H8N2O2Se | Found | ||
|---|---|---|---|
| I | II | ||
| Nitrogen | 9.24% | 9.36% | 9.48% |
Monoamino Derivative
The conversion of mononitro compound to 6-amino-2-phenylbenzoselenazole was accomplished by the action of tin and hydrochloric acid as follows:
30.3 grams of nitro compound were mixed with 42 grams of twenty mesh tin in a liter flask, immersing the latter in cold water. 175 cc. of conc. HCl were slowly added to the flask. In some cases it was necessary to apply initial heating but when once the reaction started it took place rapidly. After the effervescence had abated, the flask was heated over a free flame, under a return condenser, for two hours. The solution usually turned to a pasty mass, due to the formation of a tin double salt. The mixture was dissolved in a large volume of water and heated on a water-bath, the precipitate filtered out, washed, and preserved. The clear filtrate was treated with concentrated alkali, in excess, the separated amine collected, washed with water, dried and recrystallized from alcohol, using bone-black. The precipitate set aside was treated with strong alkali, the insoluble residue washed, recrystallized, and added to the main product. The yield was 75 per cent.