402 STUART AC'I'IOX OF XXX1.-Actiofa of Phosphorus Pentachloride on Xalicylaldehyde, By CEARLES M. STUART M.A. Fellow of St. John'g College, Cambridge, IT is stated by Henry (Ber. 2 1.35) that the action of phosphorus pentachloride on salicylaldehyde first produces dichlororthocresol, CC12H.C6H4*OH but that the further action of the pentachloride dis-places the hydroxyl-group by chlorine giving rise to orthochloro-benzalchloride C,H,CI*CCI,H; by the action of water on this at 1 i O " orthochlorobenzaldehyde C,HdCl*COH may be prepared. (See 1Yatt.s' Dictionttry 8 302.) On attempting t o prepare orthochlorobenzaldehyde in 'chis way I found t h a t if the mixture of phosphorus pentachloiide and salicyl PHOSPHORUS PENTACHLORTDE ON SALICYLALDEHYDE. 403 aldehyde was heated it was entirely carbonised whilst if it were poured into water the product always contained phosphorus ; I there-fore undertook a more complete examination of this reactim.Salicylaldehyde was added to phosphorus pentachloride in mole-cular proportion care being ta.ken to keep the mixture cool ; on pour-ing the product into water the water became heated by the decom-position of the phosphorus oxychloride and a pink oil sepamted ; on cooling this became semi-solid and after being mashed with potash and crystallised from alcohol it formed tufts of white needles melting at 78". On analysis-0.4944 gram gave 0.0984 gram Mg2P,07. 0.4058 , 0 6518 , CO,. 0.1014 , H,O. 0.5287 gram required 54-95 C.C. 2 AgNO sol., 10 corresponding to-Theory for C2,H,,C1GPO,.C . 43.80 43.74 H . 2.77 2-61 P 5.55 5.37 C1 36-89 37-06 Its constitutional formula is PO(O*C6H1~CCl2H),. The first action of phosphorus peutachloride is to displace the oxygen of the COH-group by C1 giving dichlororthocresol but this is at once acted on by the phosphorus oxychloride produced this reaction taking place according to the equation-POCl + 3CGHk(HO).COH = PO(O.C,H,.CCl,H) + 3HC1. I n this way phosphate of dichlororthocreaol is formed just as tri-plienyl phosphate is by the action of phosphorus pentachloride on phenol. Pbosphate of dichlororthocresol is not altered by boiling with a 10 per cent. solution of caustic potash; and even with a saturated solution it is not entirely decomposed the solution containing a little chloride and phosphate only.On treating its alcoholic solution with alcoholic potash however, potassium chloride at once separates but no phosphate was obtained on boiling. I n this respect i t resembles triphenyl phosphate which is not saponified by boiling with potash. It now seemed of interest t o ascertain what would take place in this reaction if the hydrogen of the nydroxyl-group were already dis 404 WERNER RESEARCHES ON CHROM-ORGA NIC ACIDS. placed by some radicle and for this purpose methyl salicylaldehyde was chosen. Methyl salicylaldehyde was added to phosphorus pentachloride in molecular proportion ; the phosphorus oxychloride produced was dis-tilled off under diminished pressure and the residue shaken up with ether and a solution of acid sodium sulphite; the ethereal solution was then dried with calcium chloride and the ether distiiled off; the residual oil distilled a t 231".On analysis 0.3285 gram gave 0.6065 gram GO and 0.11'79 gram H,O. Thpory. Found. C,H,OCl2. C . 50.33 50.26 €3. 3.98 4.18 It is therefore orthomethoxybenzalchloride C,H,( OCK,).CCl,H, podiiced by the displacement of the oxygen of the COH-group in riiethyl salicylaldehyde by Cl,. It is extremely unstable and is a t once decomposed by warm water yielding methyl sxlicylaldehyde ; it decomposes slowly in moist air and in preparing it any rise of tem-perature or prolonged contact with water must be avoided. I think i t worth remarking that when the bydroxylic hydrogen of dichlor-orthocresol is displaced by methyl the CC1,H-group is decomposed by water whereas i f the satne hydrogen is displaced by phosphoric acid the CCI2H-group is not altered by boiling with potash