CONDENSATION OF AROMATIC SULPHINIC ACIDS. 2579CCLXIV.-The lntewnolecula~* Condensatiorb o jAyomatic Sulphinic Acids. P a r t I.By THOMAS PERCY HILDITCH.THE well-known tendency of aromatic sulphinic acids to enter intocombination with other benzenoid residues through the eliminationof water is more than maintained in the corresponding acidchlorides, which, as was observed when the latter compounds wereoriginally obtained in a pure condition (Hilditch and Smiles, Ber.,1908, 41, 4113), are exceedingly reactive and unstable. In thecourse of some work on the reduction of these chlorides, it wasnoticed that, if too much heat was applied during their preparatio2580 I-IILDITCH : THE INTERMOLECULAR CONDENSATION OFor the subsequent treatment, decomposition set in, and white,crysta.lline, insoluble Compounds, sometimes accompanied by tarrymatter, were formed in considerable quantity.The present communication describes some experiments under-taken t o elucidate the nature of these by-products.It was foundthat by heating benzenesulphinyl chloride, C,H,*SOCl, or p-toluene-sulphinyl chloride, C6H4Me*SOC1, either alone at looo or in boilingchloroform, or in presence of a slight excess of thionyl chloridebeyond that needed for the preparation of the acid chlorides, asemi-solid, dark-coloured mass was obtained, from which the variouscompounds formed were separated by successive extraction withlight petroleum, alcohol, and toluene. Furthermore, in order toavoid the formation of tarry decomposition products when heat wasapplied, the condensing action of cold concentrated sulphuric acidon these two chlorides was investigated, and analogous productswere obtained, whilst, finally, it was established that the freesulphinic acid, when left for a sufficient length of time in solutionin cold concentrated sulphuric acid, underwent a similar change,and from experiments with a number of aromatic sulphinic acidsit appeared that the course of the reaction was conditioned largelyby the substituents present in the benzene nucleus.From a general point of view, it would appear that besides simpleoxidation to sulphonic acids there are the following possibilities tobe considered in this decomposition of sulphinic acids :(i) The usual formation of disulphoxides, with possible furtherdecomposition of the latter substances :(ii) (a) Intermolecular condensation of the sulphinic acids,possibly involving more than two molecules of the acid, but notproceeding beyond the sulphoxide stage ; for example :( b ) Further int,ermolecular condensation of the sulphoxides t ocomplex sulphonium bases (compare Smiles and Le Rossignol,Trans., 1906, 89,696; 1908,93, 745) :and so on.As a matter of fact, definite evidence of the production ofsulphonium derivatives has not been obtained, but both of theother reactxiom appear to take place, the one or the otherpredominating according to the manner of substitution in thesulphinic acid used.Thus, from the action of heat on benzeneAROMATIC SULPHINIC ACIDS. PART I.2581sulphinyl chloride, a quantity of diphenyl disulphide and the white,insoluble compound mentioned above was formed, whilst p-toluene-sulphinyl chloride yielded under similar conditions a mixture ofdi-p-tolyl disulphoxide and it small amount of di-p-tolyl-a-disulphone.On the other hand, benzenesulphinic, o-toluenesulphinic, anda-naphthalenesulphinic acids reacted in the presence of concentratedsulphuric acid to form varying amounts of the insoluble products,together with disulphoxides. As much as 50 per cent. yields of theinsoluble compound were obtained from benzenesulphinic acid, butonly about 20 per cent. of the two other acids was converted to thecorresponding insoluble derivative. Finally, ptoluenesulphinic,p-ethoxyphenylsulphinic, P-naphthalenesulphinic, and o-carboxy-benzenesulphinic acids gave no " insoluble " product whatever, butusually furnished sinall amounts of disulphoxides.Of these various compounds, the white, insoluble substances, whichin the first place attracted attention to this decomposition, areperhaps the most interesting.Since these were not a-disulph6nes,i t appeared probable that they had been formed by means of thecondensation (ii) (a) referred to above, but from their insolubilityin sodium hydroxide solutions it did not seem likely that any freesulphinic acid group was present in their molecules. Accordingly,the possibility of the remaining sulphinyl radicle having enteredinto the reaction had to be considered, and at first sight it appearedt,hat derivatives of diphenylene o-disulphide had been formed :HO*SO soIt soon became evident, however, from both physical and chemicalproperties of the products under investigation that they were notderived from ordinary diphenylene o-disulphide, and attention wasnext paid to a statement by Genvresse (Bull.SOC. chim., 1896, [iii],15, 421, 1038; 1898, [iii], 17,599) that in the usual preparation ofdiphenylene o-disulphide large quantities of insoluble by-productswere formed, and that under suitable conditions as much as 80 percent. yields of an insoluble compound isomeric with diphenyleneo-disulphide could be obtained from benzene, sulphur, andaluminium chloride. Genvresse suggested at the time that thesecompounds were par&condensation products, and that ordinarydiphenylene disulphides contained meta-disulphide ring systems.Recently, however, Deuss (Ber., 1908, 41, 2329) has establishedthe constitution of diphenylene disulphide as an ortho-ring systemby heating diphenylene disulphone, C6H4[ SO,],C,H,, with phosphorusVOL.XCVII. r g 2582 H~LDITCH : THE INTERMOLECULAR COXDENSATION OFpent,achloride, when a mixture of odichlorobenzene and benzene-o-disulphonyl chloride was obtained according to the equation :On trea.ting the insoluble product derived from benzenesulphinicacid according to Deuss’ directions, the author has obtained solidp-dichlorobenzene and benzene-p-disulphonyl chloride in sufficientamount for definit-e characterisation. It therefore appears that thecompounds now being described are analogous to diphenyleneo-disulphide, but are condensed into a ring system by means of theirpara-atoms :A close comparison of the properties of these compounds withthose described by Genvresse (Zoc.cit.) left no doubt that they wereidentical therewith ; for example, the colour of their solutions inconcentrated sulphuric acid is similar, bus differs from that of theortho-disulphides, whilst on oxidation a disulphone resulted identicalin properties with that, obtained by that author. Unfortunately,the compound from benzenesulphinic acid, which corresponds witha dioxide of Genvresse’s isomeric compound, could not be reducedto the latter substance, owing probably to a simultaneous ruptureof the ring system.The proof of the orientation of these substances is strikinglysupported by the fact that not a trace of the corresponding insolubleproduct could be obtained from either p-toluenesulphinic, p-ethoxy-phenylsulphinic, or P-naphthalenesulphinic acids, the positions para-to the sulphinyl group being occupied in these instances by otherradicles.The author has, however, not succeeded in deciding whether theseproducts are really analogous to diphenylene o-disulphide or whetherthey consist of an indefinitely prolonged series of *S*C,H,*S* groupsunited in para-positions.The latter alternative might be thought pos-sible in view of their insolubility in practically all organic solvents,of their high melting points, and of their not too well-defined crys-talline structure, but, on the other hand, para-substituted compoundsusually melt higher and are less soluble than the correspondingortho-derivatives, and, again, their general stability and theformation on oxidstion of disulphones similar to diphenylene diAROMATIC SULPHINIC ACIDS.sulphone lend colour to the opinion thatthe simple ring system:PART I.2583they are derived fromA determination of molecular weight, which would have definitelyestablished the point, was unfortunately quite out of the question,owing to the exceedingly slight solubility or volatility of any of thecompounds.There is, however, little reason to suppose that a par%ring systemas depicted above would be less stable, although less familiar, thanthe usual six-membered ring, for since it is generally conceded thatthe para-benzenoid atoms are almost as closely related in space asthe ortho-atoms, the above ring system will partake much morenearly of the nature of a six-membered than of the ten-memberedheterocyclic chain which at first sight it appears to be.Before describing the experimental part of this investigation, itwill be well to discuss the mechanism of the condensation.whichtake place in diphenylene disulphide syntheses, and especially thenon-appearance from sulphinic acids of any ortho-ring products.Speaking in general terms, the numerous syntheses of heterocyclicring systems which have been worked out do not permit of anychoice of orientation on the part of the molecules concerned. Thus,in the case of phenazine, the nitrogen atoms in which are situatedsimilarly to the sulphur in diphenylene disulphide, derivatives ofNby oxidation in presence of phenols (Ris, Ber., 1886, 19, 2207), orby condensation with catechol or derivatives of o-quinones (Hinsberg,‘4nnnZen, 1896, 292, 258), but the oxidation of aniline itself leadsnot to phenazine, but to the “aniline-black” dyes, in which anumber of benzene nuclei are united by means of nitrogen atomseach in a para-position with respect to the next.It seems probable that similar influences determine the course ofring formation from sulphinic acids and mercaptans ; moreover, thepreference for para-condensa.tion is emphasised in the case of sulphurcompounds by the fact that, cetem‘s paribus, in the condensation ofsulphinic acids or sulphoxides with phenolic ethers (Smiles and LeRossignol, Zoc.cit.) para-substituted products predominate overortho, the latter, indeed, being frequently not formed at all.Again, all the synthetic methods for the preparation of di-8 F 2584 HILDITCH : THE INTERMOLECULAR CONDENSATION OFphenylene o-disulphides involve much loss of product owing t o theformation of insoluble compounds, and it appears to the author thatin most of these syntheses the formation of the disulphide is due toa secondary reaction, and may be ascribed to the fact that thestarting materials are derivatives of phenyl mercaptan rather thanof the more oxidised benzenesulphinic acid. The condensation ofsulphinic acids is explained readily by the equation :and it is probable that the underlying cause of all the earlierdiphenylene disulphide syntheses is the production of temporaryhydroxylic sulphur derivatives of the type CBH,*S*OH, rather thanthe simultaneous removal of a hydrogen atom from a mercaptangroup and from a benzene nucleus by means of extraneous oxygen(compare Davis and Smiles, this vol., p.1292).Thus the chief methods extant for the synthesis of diphenyleneo-disulphides are as follows :( a ) Action of sulphur on benzene in presence of aluminiumchloride (Stenhouse, Annalen, 1869, 149, 250; Krafft and Lyons,Ber., 1896, 29, 436).( b ) Action of aluminium chloride on mercaptans or disulphides(Deuss, Rec. trav. chim., 1908, 27, 145; 1909,28, 136).( c ) Action of hot concentrated sulphuric acid on mercaptans,disulphides, or disulphoxides (Fries and Volk, BeT., 1909, 42, 1170).These reactions have been explained by the transitory formationof various oxidation and reduction products or by temporaryisomerisation of the compounds involved, but it is evident that asimpler and more comprehensive explanation of the whole seriesresults from the hypothesis that derivatives of sulphoxylic acids arefirst produced, as has been assumed by Davis and Smiles (Zoc.cit.) inthe formation of thioxanthones, and by Hinsberg (Ber., 1903, 36,109) in the formation of hydroxydiphenyl sulphide from benzene-sulphinic acid and phenol.The process is thus similar to the condensation of the sulphinicacids, and differs only in that, whilst in the latter case no ortho-condensation occurs, in the former instance derivatives of di-phenylene o-disulphide are f ormed in varying, but subsidiary, pro-portions.It should be mentioned here that phenyl mercaptan itself, onbeing kept for some hours in concentrated sulphuric acid at theordinary temperature, was converted to a mixture of a small amouuAROMATIC SULPHINIC ACIDS. PABT I.2585of diphenylene o-disulphide and about 70 or 80 per cent. ofdiphenylene pdisulphide.The decomposition of disulphoxides in cold concentrated sulphuricacid is at present under investigation.EX PE R I MENTAL.A ction of Heat on Benzene- and p-Toluene-sdphinyl Chlorides.( a ) Five grams of benzenesulphinic acid were converted to thechloride by solution in et>her and treatment with the theoreticalquantity of thionyl chloride.It is found that this method yields amuch cleaner product than the course formerly pursued of allowingexcess of thionyl chloride tlo act on the undissolved acid in the cold.The ether was subsequently evaporated, and the residue heated onthe water-bat.h for about an hour, when abundant evolution ofhydrogen chloride took place. A t the end of this period, the semi-solid product was extracted several times with boiling alcohol, afterwhich the colourless, insoluble residue, which could not be crys-tallised from even such high boiling solvents as nitrobenzene oraniline, was dried at 130° and then analysed:0.1023 gave 0.2186 CO, and 0.0321 H,O.C,,H,O,S, requires C = 58.07 ; H = 3-23 per cent.The alcoholic extract was found to contain a smaller quantity ofdiphenyl disulphide, melting at 59O, and identified with that sub-stance by the mixed melting-point method.( b ) Two equal portions of benzenesulphinic acid were taken; onewas converted into the acid chloride, and then heated with the otherfor some hours in boiling chloroform solution.As in the firstinstance, a large amount of diphenylene p-disulphoxide, togetherwith a smaller amount of diphenyl disulphide, was obtained.( c ) Equal weights of benzenesulphinyl chloride and ptoluene-sulphinic acid were heated in boiling chloroform for some time.After the evaporation of the chloroform, the product, which wasvery dark coloured, was first extracted with light petroleum, fromwhich on evaporation a pale yellow oil was obtained, which wasnot closely examined, but appeared to be phenyl-p-tolyl disulphide(Otto and Rossing, Ber., 1886, 19, 3133).The residue was boiledwith alcohol several times to remove tarry by-products, and aninsoluble powder was thus formed, which again gave anqlyticalnumbers corresponding with diphenylene p-disulphoxide.(d) Five grams of benzenesulphinic acid were heated for an hourwith an amount of thionyl chloride in slight excess of that necessaryfor complete conversion to the acid chloride. The usual evolution ofhydrogen chloride occurred, and the residue was extracted withC=58*26; H=3*492586 HILDITCH : THE INTERMOLECULAR CONDENSATION OFboiling light petroleum, which removed a small amount of diphenyldisulphide, and then with boiling toluene, from which thereseparated a quantity of a white, crystalline substance, melting anddecomposing at 180O. This proved to be a monoxide of diphenglenep-disulphid e, C6H4<y>C,H,.0.1161 gave 0.2673 CO, and 0-0398 H20.C=62-77; H =3-80.0.1192 ,, 0'2712 CO, ,, 0'0420 H20. C=62*04; H=3.91.C,,EsOS2 requires C = 62-07 ; H = 3-45 per cent.For comparison with this compound a sample of the monoxide ofdiphenylene o-disulphide was prepared from diphenylene o-disulphideby the method used by Fries and Volk (Zoc. cit.) in the preparationof the monoxide of ditolylene o-disulphide from ditolylene o-di-sulphide. Two grams of synthetic diphenylene o-disulphide, melt-ing a t 159O, were dissolved in glacial acetic acid, and dilute nitricacid (1: 5) was added until a turbidity appeared.The solutionmas set aside for twenty-four hours at the ordinary temperature,and then poured into water. The precipitate was collected andcrystallised from alcohol, when it formed colourless, glisteningprisms, readily soluble in glacial acetic acid, benzene, or toluene,more sparingly so in alcohol, and melting at 148O:0.1150 gave 0.2607 CO, and 0.0369 H,O.CI2,H,OS2 requires C = 62-07 ; H = 3-45 per cent.( e ) On similarly heating 5 grams of p-toluenesulphinyl chloridein boiling chloroform, much tarry matter was produced, and, afterevaporation of the chloroform, extraction with light petroleumyielded a white, crystalline substance, which melted at 74-76O, andappeared from its other properties to be di-p-tolyl disulphoxide.(Found, C = 61.06 ; H = 6.34. Calc., C = 60.43 ; H = 6-04 per cent.)The residue was decolorised by repeated boiling with alcohol,and was found to crystallise from boiling toluene in small prisms,which melted at 210-212O (di-p-tdyl a-disulphone melts at 212O :Kohler and MacDonald, Amer.Chem. J., 1899, 22, 219; 221O:Hilditch, Trans., 1908, 93, 1524). (Found, C =53'20; H =4.17;C = 54-22 ; H = 5-49.No t.race of diphenylene p-disulphide derivatives was observed,and it would appear that, the para-position being already occupiedby a methyl group, the reaction had taken the alternative course (i)referred to on p. 2580, in tahe presence of a certain amount of freesulphinic acid which must be assumed to have been regenerated :R-SQCl+ R.SO,H --+ R*SO*SO,*R (int'ermediate product)ZR*SO*SO,*R -+- R*SO*SO*R + R*SO,*SO,-R.C= 61.81 ; H=3-57.Calc., C = 54.20 ; H = 4-52 per cent.)AKOMATIC SULPHINIC ACIDS.PART I. 25S7Action of Cold Concendrated Szclphu& Acid om BenzenesulphinicAcid.( a ) Two grams of benzenesulphinic acid were converted to thechloride and poured into cold concentrated sulphuric acid.Hydrogen chloride was immediately disengaged in abundancethroughout the solution in the form of minute bubbles, and afterhalf an hour at the ordinary temperature, the reaction mixturewas poured on crushed ice. The solid product was separated andboiled with alcohol, thus removing a small amount of diphenyldisulphoxide, which melted at 45O.The residue (diphenylenep-disulphoxide) was dried at 130° and analysed. (Found, C = 58-22 ;H = 3-35.( b ) Ten grams of benzenesulphinic acid were left in solution inexcess of cold concentrated sulphuric acid. The mixture, whichwas at first colourless, gradually turned purple, and was eventuallyof an almost black hue. On pouring into a large bulk of coldwater, the colour entirely disappeared, and a granular, cream-coloured, solid product separated, and was collected and dried ona porous tile.The whole was then boiled with alcohol under reflux for a timeand again filtered; from the alcoholic filtrates about half a gramof diphenyl disulphoxide was obtained, which crystallised fromlight petroleum in characteristic, wax-like crystals, melting at 46O.(Found, C = 57-00 ; H = 4-20.The insoluble part of the product, when boiled for some time withalcohol, lost its cryst'alline appearance, and swelled up to a viscid,indiarubber-like mass.After removing the alcohol, however, thesubstance quickly became brittle again, and appeared gradually tobreak up into a microcrystalline powder on long keeping. Thisbehaviour was also noticed with all the previously-described pre-parations of diphenylene p-disulphoxide, and also with the sub-stituted derivatives subsequently mentioned.The substance, which was then almsst pure, was further sub-mitted to two different methods of purification.(i) A portion was boiled with toluene under reflux for some time,and was then collected and dried at 130° for some hours to removeadsorbed solvent and moisture, which was otherwise retained remark-ably firmly. Diphenylene p-disulphoxide, as thus prepared, is acream-coloured Eowder, practically insoluble in all the organicsolvents tried (even in boiling nitrobenzene or aniline), but dis-solving with a greenish-black# colour in concentrated sulphuric acid.It commenced to soften and decompose without actually melting at305O :Calc., C = 58.07 ; R = 3-23 per cent.)Calc., C = 57.60 ; H = 4.00 per cent.2588 HILDITOH : ‘I’HE INTERMOLECULAR CONDESSATION OF0.1035 gave 0.2194 CO, and 0.0298 H20.(ii) The remainder of the preparation was boiled with water for0.1353 gave 0.2685 CO, and 0.0485 H,O.C =54*12; H=3*98.0.1292 ,, 0’2540 CO, ,, 0.0401 H20. C=53.60; H=3*45.C,,H80,S,,H,0 requires C = 54.13 ; H = 3-76 per cent.An at,tempt was made to remove this molecule of water by pro-longed boiling with xylene, but a subsequent analysis showed thatthe composition of the product had not been altered. (Found,C = 53-34 ; H = 3.53.)Water thus firmly attached is inconsistent with the presence ofwater of crystallisation, and it can only be surmised that some suchhydrate formation as the following had taken place:C =57-81; H = 3-17.C,,H,O,S, requires C = 58-07 ; H = 3-23 per cent.two hours, and then collected and dried at 130° as above:,\so- /\ /Oxidation of DiphenyZene p-Disdphoxide.Two grams of diphenylene p-disulphoxide were boiled for eighthours with a slight excess of anhydrous chromic acid in glacial aceticacid; oxidation ensued, and the hot reaction mixture was filtered,and the residue washed with boiling water until all traces of greenchromium salts were removed, and then with boiling alcohol; anamorphous, white powder, which neither melted nor changed inappearance below 350°, was left.A sample dried in a vacuumdesiccator was analysed :0.0994 gave 0.1693 CO, and 0.0362 H,O. C = 46.45 ; H = 4.05.0.1380 ,, 0.2343 CO, ,, 0.0422 HiO. C=46*30; H=3*40.C,,H,0,S2,2H20 requires C = 45.57 ; H = 3-80 per cent.Redaction of Diphenylene p-Bisulphoxide.(a) Two grams of hydrated dioxide were heated for eight hourswith 5 grams of sulphur at 150O; this process reduces the orthedisulphoxide to the corresponding disulphide (Krafft and Lyons,Zoc.cit.), but on removal of excess of sulphur by means of carbondisulphide, the para-disulphoxide was found to have been un-attacked.( b ) Three grams of the dioxide were heated under pressure at160-180O with 1 gram of red phosphorus and 10 C.C. of hydriodicacid (D 1.7). Considerable pressure was generated, and the productwas poured into wat,er and extracted with benzene. A large proAROMATIC SULPHINIC ACIDS. PART I. 2589portion of insoluble matter was removed by filtration of the wholeof the liquid, and the benzene layer was then dried and evaporated.It yielded a small amount of an oil, which soon crystallised, and,when purified by light petroleum, melted at 61O; analysis confirmedthe supposition that this was diphenyl disulphide.(Found,C = 66-01 ; H = 5.01.An attempt made t o purify the insoluble product, which wasassumed to be diphenylene p-disulphide, by sublimation, led to theevolution of iodine vapotns, and further experiments showed thatthe substance contained chemically bound iodine in quantity.Analysis proved that one atlorn of iodine was present in eachdiphenylene pdisulphide residue, but as the compound was not thedesired parent substance it was not further studied; it is probablyeither an iododiphenylene p-disulphide or else a compound of thetype HS°C6H*oS*C6H,I, formed by rupture of the para-ring system :@12H7S21 requires C = 42.1 1 ; H = 2-05 per cent.Calc., C = 66-06 ; H ~ 4 ' 6 0 per cent.)0.1800 gave 0.2750 (20, and 0.0516 H,O.C=41.68; H=3.18.C&E&@,I ,, C=41.86; H=2*62 ,,Proof of the Constitution of Diphenylene p-Disulphoxide.Six grams of the disulphoxide were ground in a. mortar with 30grams of phosphorus pent>achloride, and heated in sealed tubes at220° for six hours. The contents of the tubes were poured on ice,and subsequently extracted with ether; this extract was dried, $heether evaporated, and the residue distilled in a current of steam.The aqueous distillate contained an oil which quickly solidified to amass of white needles, melting at 53O, and possessing the character-istic odour of pdichlorobenzene. (Found, C = 48-60 ; H = 2-25.Calc., C=48.98; H=2*71 per cent.)Since both 0- and rn-dichlorobenzene are liquids, the identity ofthe product was considered to be satisfactorily established.The non-volatile portion of the product was extracted with etherand shaken with di1ut.e sodium hydroxide; on evaporation of thedried ethereal solution, wax-like and not very well-defined crystalsseparated, melting at 131-1 33c ; benzene-o-disulphonyl chloridemelts at 1 0 5 O ; the mcompound at; 63O; and the p-compound at132O.Calc., C = 26.18 ; H = 1.46 percent.)The compound was further characterised by conversion into thesparingly soluble diamide, which formed small, hard prisms, andmelted at 295O. The ortho-compound melts at 233O, the meta at228O, and the para at 288O. (Found, C=29-92; H=3-89. Calc.,C = 30.51 ; H = 3.39 per cent,.)(Found, C = 26.70 ; H = 1.262590 HILDlTCH : THE INTERMOLECULAR CONDENSATION OFCondensation of Pheryl Mercaptan ilz Cold Concentrated SulphuricAcid.Five grams of phenyl mercaptan were dissolved in concentratedsulphuric acid st the ordinary temperature, and the mixturevigorously shaken to dissolve the crystalline cake of diphenyldisulphide, which rapidly formed.After twenty-four hours, thedeep purple-black reaction mixture was poured into a large bulk ofcold water, the precipitate collected, dried, and extracted suc-cessively with boiling light petroleum and with hot alcohol. Theabsence of any solid on evaporation of the former solvent provedthat no disulphide was left unattacked, whilst from the alcoholicfiltrates a quantity of colourless, crystalline material was recovered,which, after further purification from alcohol, melted at 156-159O.A sample mixed with some pure diphenylene o-disulphide possessedthe same melting point.About a gram of diphenylene o-disulphide,dissolving in concentrated sulphuric acid to a characteristic deeppurple solution, was thus obtained. (Found, C = 66.66 ; H = 4.54.Calc., C = 66.67 ; H = 3-70 per cent.)About 3 grams of a cream-coloured, amorphous powder, insolublein boiling alcohol, were left from the above extraction, and this wasboiled with acetic acid for an hour, collected, and dried at 130O.(Found, C = 67.04 ; H = 3.88.Genvresse (Zoc. cit.) states that diphenylene p-disulphide can bepurified by sublimation ; the sample under consideration was sub-mitted to purification by this means, but did not sublime sufficientlyreadily for any quantity of the purified substance to be so isolated;enough was obtained, however, in minute, white needles for adetermination of the melting point; the compound melted anddecomposed at 290-295' (295O, Genvresse).Its solution in con-cen trated sulphuric acid was of a greenish-black hue.Calc., C = 66.67 ; H = 3-70 per cent.)Condensation of Other Aromatic Sulphinic A cids in ColdConcentrated Sulphuric Acid.(a) p-ToZzcenesuZphkvk A &.-The sulphinyl chloride. on solutionin sulphuric acid, evolved hydrogen chloride copiously, and gave agreenish-brown solution, which ultimately became deep purple. Onpouring into cold water, no p-disulphide compound was obtained,and only a very small amount of disulphoxide, which melted at 76O.A similar result was obtained from the condensation of the freeacid.( b ) p-Phemetolesulphinic ,4 cid.-The acid was dissolved insulphuric acid in the usual manner, and the purple reaction mixturepoured into water after a considerable time. The only insolublAROMATIC SULPHINIC ACIDS.PART I. 2591product was a quantity of di-p-phenetole disulphoxide, which meltedat 139O (a sample of the disulphoxide prepared in the usual wayfrom p-phenetolesulphinic acid melted at the same temperature).( c ) P-Napht halenesulphinic A cid.-The condensation was con-ducted as usual ; the products of the reaction were all soluble in colddilute acid, the solution being very deeply coloured. Neitherderivatives of a p-disulphide nor any disulphoxide could be detected.(d) o-Toluenesulphinic ,4 cid.-On separation of the products ofcondensation in sulphuric acid of 5 grams of o-toluenesulphinicacid, it was found that rather more disulphoxide derivative hadbeen produced than in the other cases.The di-o-tolyl disulphoxidecrystallised from acetone in short, colourless prisms, melting at97--98O. (Found, C = 60.09 ; H = 5-06. Calc., C = 60.45 ; H = 6.04per cent.)On the other hand, only about 20 per cent. of the sulphinic acidwas converted into p-disulphide derivative in this instance ; theditolyl erne p-disulphozide was a soft, colourless, insoluble powder,which softened, without actually melting, at 280° :0.0909 gave 0.2004 CO, and 0.0375 H,O.C,,H,,O,S, requires C = 60.87 ; H = 4.35 per cent.(e) a-Naphthalenesulphinic A cid.-The amount of .di-a-naphthyldisulphoxide obtained from the condensation was very small; itmelted at 104O. A tolerably large proportion of insoluble matterresulted, but was contaminated by the presence of traces of dark-coloured products, even after prolonged boiling with various solvents.The probably still somewhat impure dinaphthylene p-disulphoxidefinally analysed softened at 275-280°, and commenced to char ata rather higher temperature :C = 60.12 ; H = 4.58.0.1902 gave 0.4760 CO, and 0.0730 H,O.C20H,,02S2 requires C = 68.98 ; H = 3.45 per cent.( f ) o-CarborcybenzenesuZpDh~nZc A cid.-A sample of this acid wasalso submitted to the condensation in concentrated sulphuric acid.The dried product of the reaction was completely soluble in hotalcohol, no pdisulphide compounds having therefore been produced.From the alcoholic solution, pa10 yellow crystals of di-o-car boxy-phenyl disulphoxide, melting at 228O, separated ; the total amountof this product corresponded with about 10 per cent. of the originalsulphinic acid employed :C = 68-26 ; H =4-26.0.1546 gave 0.2808 CO, and 0.0444 H,O. C =49.52 ; H =3*20.C,,H,,O,S, requires C = 49.71 ; H = 2.96 per cent.THE ORGANIC CHEMlSTRY LABORATORY,UNIVERSITY COLLECIE, UNIVERSITY OF LONDON