1882 DEHN AND THORPE: XO'I'E ON THE CLXXXI1.-Note on the Anhydride of Phenylsuccinic Acid. By FRANK BERNHARD DERN and JOCELYN FIELD THORPE. THE anhydride of phenylsuccinic acid has been described as melting a t 40-50' (Spiegel, Anqtalen, 1883, 219, 32), 53-54' (Alexander, An~zalen, 1890,268, 75), 150' (Bredt and Kallen, Annnten, 1896, 293, 347),and as existing in two forms, one melting at 53-54',the other at 150' (Wegscheider and Hecht, Monatsh., 1903, 24, 418). I n spite of the fact that the compound melting at 150° mas analysed and titrated by Bredt and Kallen, we are of the opinion that it is an impure form of the acid, and that phenylsuccinic anhydride exists in only one form, which melts at 53-54', The errors concerning the properties of this compound have evidently arisen owing to its remarkable instability in the presence of moisture.Thus it is apparently impossible to prepare the pure anhy- dride by distilling phenylsuccinic acid under diminished pressure, and although the distillate boils constantly, yet a considerable quantity of unchanged acid is always carried over by the anhydride vapour. The use of this method, both by Bredt and Kallen and by Wegscheider and Hecht, for the preparation of the anhydride accounts for the presence of unchanged acid in the products with which they worked. I n the following experiments the experimental details given by these investigators have been closely followed. Distillation of Phenylsuccinic Acid under Di,minished Pressure. The distillation of phenylsuccinic acid was conducted according to the directions given by Wegscheider and Hecht, about 50 grams of the acid being slowly distilled under a pressure of 16 mm.The distillate, which passed over constantly at 196O, solidified after standingANHYDRlDE OF PHENYLSUCCINIC ACID. 1883 some hours and then melted at Yrom 53-1159 product gave the following figuros on analysis : 0.2012 gave 0.4892 CO, and 0.0856 H,O. A specimen of this C = 66.31 ; H = 4-72. C,,H,08 requires C = 68.1 ; H = 4.5 per cent. CloHlo04 ,, C=61*8; H=5.2 ,, The solidified distillate was dissolved in dry ether and allowed to stand, when the characteristic crystals of phenylsuccinic anhydride slowly separated. The product melted sharply at 53-54O. Another portion of the same distillate was dissolved in hot xylene, wbich had previously been purified by distillation over sodium and the solution placed in a steam-heated oven for some days, when the solid which had then separated was isolated by filtration and washed with a little xylene.It melted at 150-153', and gave the following result on analysis : 0.1984 gave 0.4500 CO, and 0.0991 H,O ; C = 61.86 ; H = 5.55. The compound dissolved instantly in cold aqueous sodium carbonate with effervescence. Another portion of the distillate was placed in a test-tube, which after being sealed was placed in a steam-heated oven for several days. Crystals slowly separated, which, after the deposition had ceased, were isolated and found to melt at 150 -156O. The compound was instantly soluble in sodium carbonate solution with effervescence. The products melting at 150-153' and 150-156' were recrystal- lised from hot, pure xylene, and in each case small needles melting a t 168O separated from the solutions on cooling : Cl0HZ0O4 requires C = 61 43 ; H = 5.2 per cent.0.2083 gave 0.4722 CO, and 0.1037 H,O; C=61.82; H=5*53. CloHl,04 requires C = 61.8 ; H = 5.2 per cent. This was evidently, therefore, pure phenylsuccinic acid. Another portion of the solidified distillate melting at 53-115O was treated according to the method employed by Bredt and Kallen. It was thoroughly ground with cold light petroleum (b.p. 110-1 20°), and the solid residue, after being collected by filtration and washed with light petroleum, recrystallised from this solvent. The crystals which separated melted a t 150-152' : 0.2078 gave 0.4713 CO, and 0*1015 II,O.C,,Hlo04 requires C = 61.8 ; H = 5.2 per cent. The compound dissolved in dilute aqueous sodium carbonate solution with effervescence, and, when recrystallised from xylene, yielded t h e pure acid melting at 168'. C = 61.85 ; H = 5-42, VOL. LXXXIX. 6 H1884 PATTERSON AND KAYE : Formation of Phenylsuccinic Anhydride from Phenylsuccinic Acid on Treatment with Acetic Anhydride und Subsequent Distillation. Fifty grams of the acid were mixed with a large excess of fresbly distilled acetic anhydride and heated on the sand-bath for five to six hours, when the acetic acid and unchanged acetic anhydride were distilled off, as far as possible, under the ordinary pressure and the residue distilled under a pressure of 16 mm. The anhydride passed over constantly at 196-197' as a colourless oil, which instantly solidified on cooling to a hard crystalline cake melting at 53-54' : C = 67.94 ; H = 4.62.0.19'76 gave 0,4923 CO, and 0.0821 H,O. C,,H,O, requires C = 68.1 ; H = 4.5 per cent. This anhydride, when dissolved in a little dried xylene and the solution placed in a steam-heated oven, deposited no solid even after three months. A portion sealed in a dried tube and also heated at 100' for the same period of time deposited no crystals, and another portion when sealed remained unchanged after standing three months at the ordinary temperature. Some of the anhydride was recrystal- lised from dry ether, and the large monoclinic crystals obtained in this way sealed in a tube which had been evacuated by the aid of the mercury pump. After three montbs, the surfaces of the crystals remained bright, and the melting point was found to be the same as before sealing. The anhydride also remained unaltered when kept either in an evacuated desiccator or in a sealed tube filled with dry air, but on exposure to the air of the laboratory it gradually passed into the acid, a change which was almost complete after three weeks (compare Hann and Lapworth, Trans., 1904, 85, 1367). UNIVERSITY OF MANCHESTBR.