phenothiazine

C12H11N + 2 S -> C12H9NS + H2S
To 100 ml Erlenmayer flask was added 8,4 g diphenylamine (0,050 mol) + 3,2 g sulfur powder (0,100 mol) + 0,15 g iodine (catalyst). The content was mixed and thermometer inserted, flask was put into oil bath outside (!!! H2S formation during following heating !!!). The mouth of the flask was loosely covered with teflon tape to prevent air entering and oxidizing H2S back to S (excess of S would contaminate the product). H2S evolution observed at 170 C inside flask and perhaps very slow evolution even already at 150 C. The T was kept at 190-200 C (thermometer readings in melted reaction mixture) for 30 minutes so the content in the flask was liquid. Then cooled down, content broken into very small pieces (without this it dissolves very slowly!!!). Dissolved in 150 ml of isopropanol on boiling (150 ml total volume of all isopropanol used, smaller volumes used 5 times until everything dissolved, first portion served to detach the mass from the flask, only then it was possible to crush it into small pieces). Filtered hot into heated flask from which boiling isopropanol vapor heated the funnel in the mouth of the flask. Slowly cooled down to room temperature - at first small crystals observed, but later something like yellow eyes with green center appeared, finally the content solidified into thick paste so almost no solvent visible. Put into a fridge to +4 C. Sucked on Buchner funnel, washed with 15 ml of cold isopropanol (+4 C from fridge) on filter paper and sucked for 30 minutes. Only circa 75 ml of mother liquor obtained, something stayed adhering on product and something evaporated at reduced pressure (that's the reason to chill everything to +4 C before vacuum filtration and to use only vacuum level of water aspirator pump to reduce evaporation of solvent).
43,6 g of wet product obtained so at least 33,6 g of solvent (cca 25%) trapped in the product !!! because theoretical 100% yield 0,05 mol * 199,27 g/mol = 10 g.
Air dried for 3 days in dark. Last 3rd day only 0,1 g lost on last traces of solvent evaporation. Weight 8,2 g. Yield 82%. It is very fine pale yellow-green powder or better to say it is a dust (like crushed chalk, just yellow-green color, it is not toxic, substituted phenothiazines were used as 1st generation of antipsychotics).
m.p. 176-179 C (perhaps it requires another recrystallization, wikipedia 185 C, Systematic organic chemistry, by W. M. Cumming 180 C)

reagents





reagents in flask after addition and after mixing





thermometer inserted to read temperature of reaction mixture and mouth of flask loosely covered with teflon tape to prevent oxidation of H2S back to S, flask heated in oil bath, reaction performed outside because of toxic H2S formed





H2S evolution observed as very weak fumes from the flask at the temperature of the mixture 170 C (the fumes are not visible on photo due to photo limitation)





the content in flask after heating





content crushed into small pieces (otherwise it dissolves very slowly, first small portion of isopropanol helped to detach the product from flask walls), filtered hot into a heated flask in which solvent slowly boiled and heated the funnel in the mouth of the flask





dissolved product in isopropanol, after filtration





content in flask during crystallization (click on pictures to see more details, this is quite interesting)





vacuum filtration





product is very fine dust





product in a dish on the left and mother liquor in a beaker on the right