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Senin, 02 Agustus 2010

PHENYL CINNAMATE

Into a 250 ml. Claisen flask place 72 g. of cinnamic acid and 60 g. (37 ml.) of redistilled thionyl chloride. Stopper the side arm, fit the flask with a reflux condenser the top of which is connected to a gas absorption device, and mount the entire apparatus at an angle so that the condensate will not run into the side arm. Heat the mixture on a water bath, cautiously at first, until hydrogen chloride ceases to be evolved (about 1 hour), allow to cool, and add 47 g. of pure (e.g., A.R.) phenol. Heat the mixture on a water bath until no further evolution of hydrogen chloride is observed (about 1 hour). Then place the apparatus on an asbestos-centred wire gauze and heat the flask until the contents are brought just to the reflux temperature in order to complete the reaction : do not heat unduly long as prolonged heating leads to loss of product due to decomposition and polymerisation. Allow the reaction -mixture to cool and distil under diminished pressure ; collect the fraction of b.p. 190-210°/15 mm. This solidifies to a pale yellow solid, m.p. 66-69°, weighing 98 g. Grind it to a powder in a glass mortar and wash the powder with 250 ml. of cold 2 per cent, sodium bicarbonate solution. Recrystallise from rectified spirit (150 ml.) : 81 g. of pure phenyl cinnamate (white crystals) of m.p. 75-76° are obtained.

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