124 CHATTAWAY AND CONSTABLE :XV1 I.--Deriziutives of p-lodomiline.By FREDERICK DANIEL CHATTAWAY and ALFRED BERTIE CONSTABLE.THE ease with which chlorine and bromine substitute aromaticamines has led to a very complete knowledge of the simplerderivatives which they form, but very few of the correspondingiodine compounds have been prepared on account of the difficulty ofeffecting iodine substitution, and the readiness with which the iodo-anilines decompose.The action of iodine on aniline was naturally exammined when thelatter compound began to attract attention towards the middle oflast century, and Hofmann (Annulen, 1848, 67, 61; Chem. News,1864, 9, 163) thus obtained a product which, however, he did notisolate in a pure state. I n spite of the attempts of Rudolph (Ber.,1878, 11, 78), who obtained a mixture of mono- and di-iodoanilineby the action of iodine on phenylated white precipitate, and ofComstock and Kleeberg (Amer.Chem. J., 1890, 12, 493), whoprepared p-iodoformanilide by the action of iodine on silver form-anilide, little progress was made by the use of the element itself,and it was not until iodine chloride was employed that an iodo-aniline was obtained in satisfactory amount by direct substitution.Brown (Phil. Mag., 1854, [iv], 8, 201) appears t o have been thefirst to employ iodine chloride as a substituting agent, althoughhe only tried its action on some complex vegetable acids. Stenhouse(T., 1864, 17, 327), much later, allowed i t to act on aniline itself,and naturally obtained a black tarry product, from which nothingcould be isolated in a pure state. Michael and Norton (Ber.,1878, 2, 107) were the first to employ the reagent satisfactorily.They led the vapour of iodine monochloride into a solution ofacetanilide in glacial acetic acid, and obtained thus a solution ofp-iodoacetanilide. They also obtained in a similar manner fromaniline itself a dark-coloured product, from which 2 : 4-di-iodo-and 2 : 4 : 6-tri-iodo-aniline were isolated.Our knowledge of the subject beyond this point is very scanty,and is confined to a few isolated anilides, some obtained as by-products. Thus Dyer and Mixter (Amer.Chem. J., 1886, 8, 349)found that iodine had no action on oxanilide dissolved in glacialacetic acid, but that on adding concentrated nitric acid, violentaction ensued, and a di-iodo-oxanilide was formed t o a small extent.In this paper the conditions necessary t o obtain a good yield ofpiodoacetanilide, and to prepare from it p-iodoaniline, are given.A number of the simpler derivatives obtainable from the latter arealso describedDERlVATIVES OF P-IODOANILINE.125Preparation of p-lodoacetanilide, I/-\NH*CO*CH,. \- /For this purpose it is best to employ iodine monochloride dis-solved in acetic acid. Such a solution is conveniently prepared bythe action of chlorine on finely powdered iodine suspended in glacialacetic acid. The following procedure gives a good result. Finelypowdered iodine (127 grams) is added to glacial acetic acid (150c.c.), and chlorine is passed through the suspension, the latterbeing well shaken until the appearance of small, orange-colouredcrystals of iodine trichloride, which fall as a sandy precipitate,shows that all the iodine has been converted into iodine mono-chloride. The solution must now be thoroughly shaken withsufficient finely powdered iodine t o react with the small quantityof the trichloride formed, and when this completely disappears thesolution is ready for use.To 135 grams of acetanilide in 150 C.C.of glacial acetic acid asolution of iodine monochloride, prepared as above, containing127 grams of iodine, is added with continual agitation. Someheat is developed, and a dark brown solution is formed, whichremains clear for a few moments, but as the reaction proceedspiodoacetanilide crystallises out.After twelve hours two litresof water are added to precipitate the anilide. This is collected,washed with water and then with dilute alkali, and finallycrystallised from about 400 C.C. of alcohol. After three crys-tallisations the piodoacetanilide is obtained in large, colourlessrhombs, melting a t 184O. The yield is about 90 per cent. of thetheoretical. In these circumstances the iodine alone substitutes,the chlorine combining with the displaced hydrogen, and not sub-stituting t o any recognisable extent.Preparation of p-Zodoaniline, I/-'NH,.pIodoaniline is best obtained from the acetyl compound byhydrolysing the latter with alcoholic sodium hydroxide. Onehundred grams of piodoacetanilide (1 mol.) are added to a solutionof 30 grams (2 mols.) of sodium hydroxide in 500 C.C.of alcohol, .and the mixture is boiled gently for twelve hours. On pouring thecooled mixture into three or four times its bulk of water, theaniline separates. p-Iodoaniljne, when obtained in this way, isnearly pure, but has a slight, brown colour. This may be removedby crystallisation from alcohol, in which the aniline is very soluble,or by distillation in a current of steam. When pure it is colourless,and melts a t 61-62O. It may be heated for some time to 190°without decomposition, but if heated above 200° it decomposes.\--126 CHATTAWBY AND CONSTABLE :p-Iodopropionanilicie, H- CO*C,H,. \-/This compound is formed with considerable evolution of heatwhen p-iodoaniline is added to an equivalent quantity of propionicanhydride.It crystallises in two polymorphic forms. When asolution in alcohol is cooled a liquid is obtained, which, on beingtouched with a glass rod, deposits an unstable modification; thisseparates in minute, colourless needles, forming a felted mass. I na few minutes the unstable form transforms into the stable modifi-cation, the felted mass crumbling away, and the stable form fallingto the bottom of the beaker as a shower of small, granular crystals:CgHi,ONI requires I = 46.15 per cent.0.2101 gave 0.1787 AgI. 1=45.97.Benzo-piodoanilide, I/-\NH*CO*C,H,.This compound is easily prepared by the action of benzoyl chlorideon piodoaniline in the presence of dilute aqueous potassiumhydroxide.It crystallises from alcohol in colourless prisms, meltinga t 222O:\/0.2144 gave 0.1573 AgI. 1=39*65.C,,H,,ONI requires I = 39.29 per cent.NO,o-Nitro benzo-p-iodoanilide, I/-\N H *CO/-\ \-/ \-/ -This crystallises from alcohol, in which it is very sparingly soluble,0.2646 gave 0.1681 AgI.in long, thin prisms, with a faint yellow tinge, melting a t 208O:I=34*34 per cent.C,,Hg03N,I requires I = 34-48 per cent.m-Nitro b enzo-piodoanilide.This derivative crystallises from alcohol in long, pale yellow0.2115 gave 0.1344 AgI. 1=34*35.’ prisms, which melt a t 202O:C,,H,O,N,I requires I = 34-48 per cent.p-Nitro benso-piodoanilide.This substance is even less soluble in alcohol than the correspond-It cryatalliaes in very slender, pale yellow, ing meta-compound.needleshaped crystals, melting at 269O DE HIVATIVES OF P-IODOANILINE.1270.2069 gave 0.1315 AgI. I=34*35.C,3H,03N21 requires I =34.48 per cent.The nitrobenzo-piodoanilides are best prepared by grindingtogether equivalent quantities of the corresponding nitrabenzoylchlorides and piodoaniline, moistening with a little ether tofacilitate interaction, and adding a concentrated solution of sodiumcarbonate from time to time until, on keeping, the liquid remainsdefinitely alkaline.I/-\N H-CO-CH,*C~H,. \-/ Yhenylace to-p-iodoa~~ilide,This compound is obtained by the action of phenylacetyl chlorideon piodoaniline dissolved in ether in the presence of an equivalentamount of pyridine; it crystallises from alcohol, in which it ismoderately soluble, in small, needle-shaped crystals, melting a t200° :0.2265 gave 0.1562 AgI.I=37*27.C1,Hi20NI requires I = 37.65 per cent.This substance is easily prepared by heating together a mixtureof equivalent quantities of piodoaniline and phthalic anhydride toabout 180O. 'It is very sparingly soluble in alcohol, and sparinglyso in glacial acetic acid. It crystallises from the latter in long,slender, colourless prisms, melting a t 235O. The compound originallyprepared by Gabriel ( B e y . , 1878, 11, 2261) was evidently not suffi-ciently purified, as he gives 227-228O as its melting point.o-Nitro b enzaldehyde-p-iodophenylhydrazone,NO,I/-\NH* N : c d7 \-/ \-/ *This compound, prepared from p-iodophenylhydrazine (Neufeld,Annalen, 1888, 248, 98), crystallises from alcohol, in which it issparingly soluble, in deep garnebred prisms, which melt anddecompose at 196O:0.2120 gave 0.1355 AgI.1=34*54.C1,Hl,O2N3I requires I = 34.58 per cent128 CHATTAWAY AND COSSTABLE ;m-Nitro b enzalde h yde-p-iodo ph en yl hydraz o n e .This compound is sparingly soluble in alcohol, giving a deeporange-coloured solution, from which i t crystallises in clusters ofsmall, bright, scarlet prisms, melting and decomposing a t 148O :0.2059 gave 0.1326 AgI. I=34.81.C,,H,,O,N,I requires I = 34-58 per cent.p-Nitrob enzaldehyde-p-iodophenylhydrazone.This crystallises from alcohol in slender, garnet-red prisms, which0.2363 gave 0.1517 AgI. 1=34*70.melt and decompose a t 158O:C,,H,,0,N31 requires I = 34.58 per cent.C'innamaldehyde-p-iodopheny lhydrazone,l/-\N K ON: C H C I1 : CH C,Trf,.\-/This compound crystallises from alcohol in bright yellow needles,0-2049 gave 0.1379 AgI. I=36*37.which melt and decompose at. 1 4 0 O :C,,H,,N21 requires I = 36.46 per cent.This azo-compound was obtained by combining diazotised p-iodo-aniline with phenol in alkaline solution. It crystallises from alcoholin light, golden-brown plates, melting a t 172O, which, when dry,appear maroon coloured with a golden-yellow lustre :0.2009 gave 0.1450 AgI. 1=39.01.C,,H,ON,I requires I = 39.17 per cent./-\\-/\d' \-/ p-lodob enzeneazo-&naphthoJ, I/-\N :N/ .' 'OHThis compound was similarly prepared from 8-naphthol. It isonly very sparingly soluble in boiling alcohol, but is moderatelysoluble in boiling acetic acid, from which it crystallises in dark redprisms wit,h a greenish, metallic lustre, melting at 178O:0-1941 gave 0.1213 AgI.I=33*78.C,,H,,0N21 requires I = 33-93 per centDERIVATIVES OF P-TODOAWILINE. 129p-lodoaniline reacts readily with ethyl or methyl chloroformate toform the corresponding carbanilate. The reaction is best carriedout by mixing an equivalent amount of the chloroformate with theaniline dissolved in a little dry ether, and, when the vigorous actioiihas moderated, adding enough pyridine to combine with thehydrogen chloride formed, then driving off the ether by heatingfor a short time on the water-bath. After tlioroughly washing theproduct with dilute hydroch1or;ic acid, it is recrystallised fromalcohol.E t iiyl p-lodo phenyl car bnma t e, I/-\ , ,i Y H.CO,*C,Ff,.This ester crystallises from alGoho1, in ~ : ~ i c h it is very soluble, in0.1943 gave 0.1570 AgI.1=43*67.slender, colourless, prisms, melting a t 1 1 7 O :C~13100zNI requires I = 43-61 per cent.Methyl p-lodophenylcarbamate, .I/ --\?z €1. C(.),*CH,. \-/This crystallises from alcohol in colourless plates or long, flattened0*1610 gave 0.1371 AgI. 1=46*03.C8H80zNI requires I = 45.82 per cent.pIodoaniline also reacts readily with ethyl oxalate o r ethylmalonate when the substances are heated together, forming thecorresponding anilic esters or anilides. The anilic ester or anilideis obtained in greater amount, zccording as the ester or the anilineis in excess.They can easily be separated, as the anilides arealmost insoluble in alcohol.prisms, which melt a t 142O:Ethyl p-lodo-oxanilate, I/-'NH*CO* CO,*C,H,. \-/This ester is almost exclusively formed if piodoaniline (1 mol.)is heated for about ten minutes t o 170° with five times its weight(8 mols.) of ethyl oxalate. It crystallises from boiling alcohol, inwhich it is moderately soluble, in colourless, crystalline plates,melting a t 153O:0,1678 ga63 0.1238 AgI. 1=39*88.C,oH,,03NI requires I = 39.78 per cent.s-Di-piodomalolzanilida I/-\N H-CO CH,* CO* N H/-\I,\-/ \-/pIodoaniline (1 mol.) was dissolved in three times its weight ofethyl rnalonate (4 mols.), and the liquid heated to 170° for tenVOL.cv. 130 DERIVATIVES OF P-IODOANILIN~:.minutes. On diluting the hot liquid with alcohol and cooling,s-di-p-iodomalonandide separates. A yield of 20 per cent. of thetheoretical, calculated from the weight of aniline used, was obtained.It crystallises from boiling glacial acetic acid, in which it is sparinglysoluble, in slender, colourless needles, melting and decomposing at267O :0.2009 gave 0.1861 AgI. 1=50.07.C1,H1202N212 requires I = 50.17 per cent.Ethyl p-lodonzalonatailat e , I/-'\N I i * CO-CH2*C0,*C2H,. \--/This compound was deposited by the filtrate from t h e previouslydescribed compound, after concentration. A yield of about 50 percent. of the theoretical, calculated from the weight of aniline used,was obtained.It crystallises from boiling alcohol, in which i t isreadily soluble, in colourless, crystalline plates, melting a t 120° :0.2394 gave 0.1690 AgI. 1=38*15.CllH120,NI requires I = 38.11 per cent.It has been shown by Chattaway that when carbamide is heatedwith any arylamine, ammonia is eliminated, and a monoaryl- anda s-diaryl-carbamide are produced, the former or the latter beingobtained in preponderating amount according as the carbamide orthe base is present in excess. p-Iodoaniline reacts with carbamideas do other arylamines.p-Iodoaniline (I mol.) was mixed with carbamide (7 mols.), andthe mixture heated on an oil-bath at 180° until ammonia ceased tobe freely evo1vq.d. The light brown solid thus produced was2owdered and extracted first with water and then with boilingalcohol. The residue, which consisted of s-di-p-iodophenylcarbamide,amounted to 60 per cent. of the theoretical obtainable from theaniline used. s-ni-p-iodophe.l.LyZcarbanzide is insoluble in alcohol,and almost insoluble in glacial acetic acid, but is moderately solublein boiling nitrobenzene, from which it crystallises in small, colour-less, needle-shaped crystals, which remain unmelted at 350O. (Found,I = 54-81.This compound was first obtained by Vittenet (Bull. SOC. cham.,1899, [iii], 21, 305) by heating piadoaniline with a solution ofcarbonyl chloride in toluene.Cl3Hl,ON2I2 requires I =54.71 per cent.THE DISTILLATION OF COAL IN A VACUUM. 131p-lodophemylcarbam2.de, I/-\NH*CO*NH,. \-/This compound is deposited by $he alcoholic extract from theproduct previously described after concentration. It is readilysoluble in boiling alcohol, and crystallises from this solvent incolourless plates, which remain unmelted a t 300° :0.2330 gave OZ2089 AgI. 1=48.46.C,H,ON,I requires I = 48.44 per cent.OXFOILD.UNIVERSITY CHEMICAL LABORAI ORY