acid washed neutral twice with 250 ml of saturated sodium chloride solution each time dried over sodium sulphate and the organic solvent is largely distilled off at 40 u00b0 bath temperature 20 kpa the residue is distilled over a column having a length of 20 cm whereby firstly residual solvent is removed at 50 u00b0 bath temperature 20 kpa and then the bath temperature is increased to 80 u00b0 and the vacuum is increased to 1 4 kpa during the increase in the internal temperature a forerun of about 1 g is removed and then the 2 4 bis trifluoromethyl benzaldehyde obtained distils over at 56 u00b0 1 4 kpa as a colourless liquid table ii______________________________________reaction reaction amount oftemperature time base purityt x y yield gc ______________________________________ 30 u00b0 20 min 0 16 mol 70 98 27 2 ml 20 u00b0 15 min 0 16 mol 70 98 27 2 ml 10 u00b0 3 min 0 16 mol 70 98 27 2 ml 10 u00b0 5 min 0 13 mol 70 96 22 1 ml ______________________________________ 1 h nmr cdcl 3 7 99 d 1h j 8 1 hz 8 05 s 1h 8 27 d 1h j 8 1 hz 10 44 m 1h ppm ms peaks at m e 242 m 241 m h 223 m f 222 m hf 213 m cho 195 194 164 163 145 144 a a solution of 68 ml 0 4.