362 BARNETT AND SMILES : DERIVATIVES OFXL.-Derivatives of X-P~eny~henazot~~Lioniunz.Pccrt III.By EDWARD DE BARRY BARNETT and SAMUEL SMILES.IN two previous communications (Hilditch and Smiles, Trans., 1908,93, 145, 1687) the products obtained by the condensation of thenitrodiphenylamine sulphoxides with phenol and phenetole weredescribed. Reasons were then adduced for regarding these subS-PHENY LPHENAZOTHIONIUM. PART 111. 363stances as derivatives of S-phenylphenazothionium, the process bywhich they are formed being formulated as follows:NH NH8/\Ac C,H,*O€€I n the meantime the study of the intramolecular rearrangementof the diphenylamine o-sulphoxides (Trans., 1909, 95, 1253 ; thisvol., p. 186) has enabled us t o obt,ain evidence throwing furtherlight on the formation and reactions of these substances.Wehave therefore extended our experiments with derivatives of thisgroup in order further to discuss their constitution and chemicalbehaviour.I n the Grst part of this paper the constitution of these derivativesis discussed, and in the latter part the factors governing theirformation are considered.I.--The Constitution of the Derivatives.When dinitrodiphenylamine o-sulphoxide is treated with a phenolor its ether in presence of concentrated sulphuric acid, the sulphatesof t,he dinitro-compounds of the group are formed. In discussingthe constitution of these substances, it has been pointed out (Trans.,1908, 93, 1688) that on general grounds only three alternativestructures can be entertained ; these respectively involve theN-aryl (I), the C-aryl (11)), and the S-aryl (111) arrangements:ArH - N O A ~ N Ar/\A/\I I I I/\/\/\O"\/O"N(/\/"NO2 I l lS SAAc Ar(111.364 BARNETT AND SMILES : DERIVATIVES OFAmple reasons have been already given for discarding the formeralternatives ( I and 11) and for accepting the S-aryl structure as thetrue representation of these salts.Later experiments have servedstill further to strengthen this conclusion.The N-Aryl Structure.-In order further to test the validity ofthis structure, we have prepared N-phenylthiodiphenylamine bymeans of the reaction devised by I. Goldberg (Ber., 1907, 40, 4525)for the phenylation of aromatic amines, and we find that theproperties of this substance and its nitro-derivatives are entirelydifferent from those of the compounds the structure of which is inquestion.N-Ph e n y 1 t hiodiph emylaniline.A mixture of 10 grams of iodobenzene, 5 grams of thiodiphenyl-amine, 4 grams of potassium carbonate, and 0.5 gram of copperiodide was boiled with excess of bromobenzene for eighteen hoursin a flask provided with a reflux arrangement. Water was thenadded, and the volatile benzene derivatives were removed with theaid of a current of steam.The solid residue was boiled withalcohol, and the solution was separated from the residue byfiltration. The product reEaining in the filtrates usually containsa considerable quantity of unchanged thiodiphenylamine, but bycrystallisation of the more soluble portion, N-13iLenyZt?Liodiphenyl-amine was obtained in short, yellow prisms, which melted at89-90° :0.2006 gave 0.5'790 CO, and 0.0906 H,O.I n chemical behaviour the substance closely resembles N-methyl-thiodiphenylamine.It is soluble in concentrated sulphuric acid,giving a crimson solution, being then partly oxidised to the phenazo-thionium salt. The basic properties, if, indeed, any are manifest,are very weak, since no salts could be isolated. When nitratedunder the conditions required to obtain the dinitro-sulphoxide fromN-methylthiodiphenylamine, the substance furnishes a mixture ofpolynitro-compounds, which could not be satisfactorily separated.However, it is sufficient for the present purpose to recordthe properties of the nitrated substance.It is crystalline,yellow in colour, insoluble in and unattacked by aqueous alkalihydroxide, and, like the corresponding N-methyl derivative, maybe condensed with phenetole in presence of concentrated sulphuricacid. The followingtable is given in order to emphasise the distinction between thesederivatives and the condensation product obtained from dinitro-diphenylamine o-sulphoxide and phenetole ;C=78.7; H=5*0.C,,H,,NS requires C = 78.5 ; H = 4.7 per cent.It is very soluble in cold glacial acetic acid8-PHENY LPHENAZOTHIONIUM. PART 111. 365Condensation productN-Phenylthio- Nitro- from phenetole and dinitro-diphenylamine. derivatives. diphenylamine sulphoxide.Colour of base ... .,.,,,... Yellow Yellow Crimson and fluorescentAction of acids on base.No salts formed Stable green salts ob-Action of H,S04 and - Condensation Salt formed, but noin solution.tained.phenetole. further action.The fact that N-phenylthiodiphenylamine and its nitro-derivatives do not form salts, whilst the green salts in questionare quite stable, is alone sufficient to show that the latter do notcontain the N-aryl structure. Moreover, if these salts contain theN-aryl structure (I), it is clear that the action of alkali mustfurnish a dinitro-N-phenylthiodiphenylamine, but instead theyyield crimson, fluorescent bases (Trans., 1908, 93, 151, 1693), whichare entirely different from the nitro-derivatives of N-phenylthiodi-phenylamine. For these reasons the N-aryl structure for thesecompounds must be finally rejected.The C-AryZ Structure (II).-It was previously shown (Trans.,1908, 93, 1689) that if this structure were correct, the substancemust be formed by simultaneous oxidation of the phenol and thephenazothionium salt (IV) :NOHVV.1According to this view, the latter substance would appear as anintermediate product formed from the dinitro-sulphoxide (I) by theaction of the concentrated acid (see Trans., 1909, 95, 1261).Muchevidence has already been adduced for abandoning this view, but,since it is now possible to obtain the dinitrophenazothioniumhydroxide in the pure condition, we have been able to submit thequestion to direct test. Numerous attempts were made to effectthe condensation of this phenazothionium hydroxide with phenetoleby means of concentrated sulphuric acid both without and inpresence of a mild oxidising agent, but they were unsuccessful.In these experiments the greater portion of the phenazothioniumhydroxide was unat*tacked, whilst the remainder was converted intoa tarry material from which no definite product could be isolated.However, more cogent argument against this structure is furnishedby a comparison of the properties of the dinitrophenazothioniumhydroxide and the phenolic compound the constitution of which issought.It has been elsewhere shown (Trans., 1909, 95, 1256) tha366 BARNETT AND SMILES : DERIVATIVES OFin the former substance (IV) the basic function of the azothioniumgroup is depressed by the presence of the nitro-groups in theadjacent benzene nuclei; in fact, the substance does not form saltswith aqueous mineral acids.But on examining the formula (11)which represents the C-aryl structure for the phenolic compound,it will be seen that, if this were correct, the substance must exhibita similar lack of basic properties, for it cannot be supposed thatthese would be strengthened by the linking of a phenolic residueto one of the aromatic nuclei in the azothionium complex. Sinceall the dinitro-compounds of this group which have been obtainedexhibit well-defined basic properties, it is clear that they cannotbe derived from the C-aryl structure, which for this and otherreasons (Trans., 1908, 93, 1689) inust now be finally rejected.The S-Aryl Structure.-This constitution now remains as theonly possible alternative, and, as previously shown (Trans., 1908,93, 1687), it is to be anticipated from the characteristicbehaviour of the thionyl group in aromatic sulphoxides, since thelatter substances are converted into sulphonium salts by treatmentwith aromatic compounds in presence of phosphoryl chloride orsulphuric acid.It will now be shown that the S-aryl structure isfurther justified by the analogy between these substances and theparent phenazothionium compounds.I n discussing the mechanism of the change of the ifnino-thionylstructure into the azothionium arrangement, it has been demon-strated (this vol., p. 186) that in this reaction the thicmyl salts arefirst formed, and that these are subsequently converted into thequinonoid compounds.The process, reduced to its simplest terms,is represented as follows (V and VI):NH N/\OH U1 dl+ H,O/\/\\A/\/t 1 - 1 IS S/\HO Ar kr(VII.) (VIII.)Now, when the S-aryl salta are treated with aqueous alkalihydroxide, they are converted by loss of the elements of mineraS-PHENYLPHENAZOTHIONIUM. PART 111. 367acid into crimson, fluorescent bases (Trans., 1908, 93, 145), forwhich the quinonoid structure (VIII) is accordingly the only repre-sentation possible. It is clear that in this process the sulphoniumhydroxides (VII) must be first produced by the action of thealkaline reagent, and on referring to the formulae it will be seenthat the conversion of these substances into the quinonoid baseis strictly analogous to the change of sulphoxide salt into thequinonoid sulphonium salt (V and VI).I n either case thequinonoid arrangement is produced by removal of hydroxyl fromthe quadrivalent sulphur group.I n both series it is possible to obtain the quinonoid derivativesin the hydrated condition. I f the green 8-aryl salts are boiledwith water or treated with cold aqueous sodium carbonate, thecrimson hydrated bases are formed (Trans., 1908, 93, 151, 1693).I n a, previous paper dealing with the salts and hydrates ofphenazothionium (this vol., p. 186), we have shown that there isgood reason for representing this additional molecule of water asforming the ammonium grouping (as in I X ) :HO-NOHS(TX.)61If this hypothesis is extended toformula (X) forecasts the possibilityHO-N-H/\//\/A! I l l\A/\/ sAir)the S-phenyl derivatives, t,heof the existence of two seriesof salts: the green or yellow sulphonium salts (type 111), asobtained with the dinitro-derivatives, and a red series, which wouldbe the ammonium salts (type X).We have been able to showthat the latter exist. The sulphonium grouping in the dinitro-derivatives which give the green salts is of moderate basic power,and it is evident that if these red ammonium salts exist they mustbe sought for in derivatives where the basic properties of thesulphoniurn group are still further depressed. With this object inview the tetranitro-derivative of this series was investigated.Tetranitro-Sphenetytphenuzothionium.Finely powdered tetranitrodiphenylamine o-sulphoxide was mixedwith a large excess of concentrated sulphuric acid.Some of thesulphoxide dissolved, but the greater portion remained in suspen-sion. Excess of phenetole was then gradually added to the coldmixture, which was constantly agitated and kept within the limitsof atmospheric temperature. As increasing quantities of th368 BARNETI' AND SMILES : DERIVATIVES OFphenolic ether were added, the suspended sulphoxide dissolved,forming a deep red solution. When renewed addition of thereagent produced no further change, the mixture was passedthrough glass wool, and then poured on a large bulk of meltingice. The now insoluble reddish-brown material was collected, wellwashed with cold water, and finally dried at.the atmospheric tern-perature. This crude material was purified by rapid extractionwith acetone in a Soxhlet apparatus. The acetone solution result-ing from this operation was concentrated on the water-bath, andthen, when cold, it was mixed with a little ether. The first pre-cipitate was removed by filtration and rejected; but on adding afurther quantity of ether to the filtrates, tetrunitro-S-p7LenetyZ-p7~enazotlzioniurr~ sulphaie was gradually precipitated in minute,reddish-brown crystals, Analysis was conducted with two samplesfrom different preparations :0.1877 gave 0.2728 CO, and 0.0553 H;O. C = 39.65 ; H = 3.2.0.1328 ,, 0.1937 CO, ,, 0.0391 H,O. C=39.8; H=3.2.C,,H,309N,S,H2S0, requires C = 40.2 ; H = 2.5 per cent.The substance does not melt below 250O; it is insoluble in wateror cold alcohol, and soluble in acetone.The solutions in the last-named solvent are not fluorescent, like those of the dinitro-compounds.The base is readily obtained in the hydrated form by boiling thesulphate with water. A sample, which had been dried in thesteam-oven, was analysed :0.2014 gave 0-3404 CO, and 0.0652 H,O.Tetrunitro-S-phenetylphenazot?Lioniurn hydroxide is insoluble inFinally, on comparing the dinitro-compounds of the S-phenylC =46.1; H = 3-6.C20H,,0gN,S,H,0 requires C = 46.4 ; H = 2*9 per cent.water, and very sparingly soluble in boiling alcohol,series (XI) with those of the parent series (XII):N Nb,H,*OEt 6H(XI.) (XII.)it is seen that in the former class the basic function of the sul-phonium group is appreciably increased by the substitution ofaryl for hydroxyl at the quadrivalent sulphur.But it may beremarked that this increase in basic power is to be expected fromthe general influence of this substitution in simpler compounds oS-PHENY LPHENAZOTHIOKIUM. PART 111. 369quadrivaleiit sulphur.this effect:The following series is quoted to illustrateHO c! H *OEt HO C,H; OE t g > s < g HO>S<OFi-I HO>S<C, H, 0 Et(or tho) S ul phiirous (or tho) Phenetylsal phinic (ortho) Phenetyl-Very weak base.acid. acid. sulphoxide.HO C6H,*OEtEtO'C,Ii4>s<C,B;OEtTriphenet ylsulphonium.Strong base.and it is clear that the successive replacement of the hydroxylgroups in ortho-sulphurous acid gradually increases the basic powerof the group in question.From these considerations it is seen that the chemical behaviourof the condensation products agrees very closely with that whichwould be expected for them on the basis of the S-aryl structurefrom analogy t o the simpler phenazothionium hydroxides. Moreover,since all other possible structures have been shown to be untenable,the S-aryl constitution must now be regarded as finally established.11.-Formation of the S-Arylphenazothionium Arrangem\en,t.The factors which control the formation of these derivatives areto be found in the nature of the diphenylamine o-sulphoxideemployed and in the group which is to enter the thionium arrange-ment.( a ) The Influence of the Character of the Sdphoxide.--It hasbeen previously mentioned that the derivatives of the 8-aryl seriesare obtained by the condensation of a diphenylamine o-sulphoxidewith an aromatic compound in presence of concentrated sulphuricacid (see formulz on p.363). But by no means do all thesulphoxides of diphenylamine behave in this manner. Previousexperiments (Trans., 1909, 95, 1253) have shown that, whentreated with acid reagents, some of these sulphoxides are imme-diately converted into salts of phenazothionium (V and VI), andthe latter substances are incapable of undergoing the requiredcondensation. It is therefore evident that the answer to thequestion whether a given sulphoxide can yield the S-aryl derivativesby this reaction must depend on the stability of the sulphoxidein presence of the strong acid.If the sulphoxide is instantaneouslyconverted by the acid into the phenazothionium salt, the 8-arylderivative will not be formed; but if this conversion does not takeplace, or if it is sufficiently slow to enable the condensation to beeffected before it has proceeded far, then the S-aryl derivativesThese will be considered separately370 BARNETT AND SMILES : DERIVATIVES OFcan be obtained.the six sulphoxides which have been examined :This is entirely borne out by the behaviour ofSulphoxide.Diphen ylaminc o- sulph oxideN-Methyldiphenylamine ),pp-Dinitrodiphenylamine ,)Diisonitrodiphenylaniine ,,Dinitro-N-methyldiphenylamineTetrariitrodiphenylariiine o-sulph-o-sulphoxide.oxide.In concentrated H2S04In concentrated H2S04.with phenetole.Immediate rearrangement No condensation.Rearrangement slow Condensation withfresh so111 tions.fresh solutions.fresh solutions.* ) 9 ) Y ) 9 9$ 9 1, Condensation with3 7 $ 9 Condensation withNo rearrangement ap Condensation.prtxiable.Of these six cases, those of the dinitro-derivatives are the morenoteworthy. When phenol is added to freshly prepared solutionsof these substances, the 8-hydroxyphenyl derivatives are readilyformed, and the yield is almost quantitative; but with solutionswhich have been kept some hours, the required reaction does nottake place. The intramolecular rearrangement of these sulphoxideswhich thus militates against the formation of the S-aryl derivativesis favoured by the increase of the basic function of the thiodi-phenylamine nucleus (this vol., p.186). Hence it is clear that theintroduction of basic groups in the sulphoxide will tend to hinderthe formation of the 8-aryl compounds, and the addition of acidicgroups will tend to exert a favourable influence. This favourableeffect seems to attain a maximum in the dinitro-compounds, forthese are more reactive and furnish better yields than the tetra-nitro-derivative. It appears that in these substances the thionylgroup is still sufficiently basic to yield readily the sulphoxide salts(V) which form the preliminary stage of the reaction (Smilesand Le Rossignol, Trans., 1906, 89, 697). The more sluggishcondensation of the tetranitro-derivative may be ascribed to thelessened tendency to form these salts, which is due to the furtheraddition of acidic substituents.( b ) The Nature of the Groups zuhLich may enter the ThLionium,4 ~ralzgem~ent.-Experiments have shown that the chief types ofsimple aliphatic compounds do not furnish these sulphoniumderivatives under the normal conditions of the reaction.Theformation of these derivatives seems confined to compounds con-taining an aromatic complex or an arrangement similar thereto.The capability of an aromatic compound to condense with thediphenylamine sulphoxide is determined by the reactivity of thearomatic nucleus in the compound in question, and this, in turn,depends on the number and nature of the substituents present.Of the aromatic hydrocarbons, benzene and toluene are inactive,but if suitable groups are introduced, the condensation can bS-PHENYLPHENAZOTHIONl UM.PAnT 111. 371readily effected, for example, m-xylene acts very sluggishly, butfrom mesitylene the sulphonium base is easily obtained.Dinit ro-S-m esit ylphenaao t hionizcm.Excess of mesitylene was slowly added with constant agitationto a freshly prepared ice-cold solution of pp-dinitrodiphenylaminesulphoxide in concentrated sulphuric acid. After each additionof the hydrocarbon, a sample of the liquid was withdrawn andpoured into cold water. When the precipitate obtained in thismanner was of a pure green colour, the addition of the hydro-carbon was interrupted, and the reaction mixture was poured onpowdered ice.The sulphate was then collected and washed, firstwith water and then with ether, to remove adherent mesityleneand other oily impurities. After renewed washing wit’h water, thesalt was triturated with a cold aqueous solution of sodium car-bonate. The solid base was collected, and washed with water untilfree from alkali. After purification, diiLit4.o-S-mesitylphenazo-thionizcm hydroxide was obtained in minute, chocolate-browncrystals of high melting point. A sample which had been drieda t looo was analysed:0*2024 gave 0.6660 CO, and 0.0868 HiO.The base is sparingly soluble in hot water, giving purple solutions,and readily so in cold acetone.Generally speaking, however, the reactivity of the hydrocarbonsis sluggish in comparison with the hydroxy- and amino-derivativesc-if benzene. Qualitative experiments made with a wide range ofmaterial have shown that almost all aromatic compounds containingthese groups alone readily furnish the 8-aryl derivatives with thedinitro-sulphoxides.But since the products obtained from thesesubstances for the greater part resemble the h‘-hydroxy-phenyl and-phenetyl derivatives which have already been described in detail,no particular interest would have been served by the isolationand analysis of each compound. However, the case of theS-salicyl derivative is worth especial mention, since it occurs as atrue carboxy-thetine.C=59*8; H=4*7.C2,H,,04N,S,H20 requires C = 59.3 ; H = 4-47 per cent.Dinit ro-S-salicylyl~enazo ghionium.The condensation of ppdinitrodiphenylamine sulphoxide withsalicylic acid was effected in the usual manner.The crude product,after being well washed with cold water, was dissolved in diluteaqueous alkali hydroxide. The solution was then clarified byfiltration, and then mixed with dilute sulphuric acid in exactlyVOL. XCVII. c 372 BARNETT AND SMILES : DERIVATIVES OFsufficient quantity t o precipitate the thetine. No suitable solventcould be found for the recrystallisation of this substance. It issoluble in hot nitrobenzene, but on cooling the solution it is pre-cipitated in the amorphous condition. Analysis was made witha sample which had been washed with alcohol and dried in thesteam-oven :0-2036 gave 0.3858 CO, and 0.0608 H,O.0.1510Dinitro-S-salicylplenazothioniu~~~ hydroxide forms a mustard-yellow, amorphous powder of high melting point.It is worth observing that the substance obtained in this manneris not the sulphate of the S-aryl base which might be expectedfrom analogy to the S-hydroxyphenyl derivative.Evidently thesulphonium salt is internally formed with the carboxyl group, theadditional molecule of water being present as with most thetinesand betaines :C=51*6; H=3*2.,, 12.5 C.C. N, at 2 3 O and 750 mm. N=9.4.C,,H,,O,N,S requires C = 51.6 ; H = 2.9 ; N = 9.7 per cent.NHThe substance is more stable than the salts of the S-hydroxy-phenyl series, being unattacked by boiling water; but it is solublein alkali, giving deep red solutions of a, sodium salt.Turning to the condensation products obtained from naphthalenederivatives, it has been found that the wide scope of the reactionobserved with benzenoid compounds is well sustained.Althoughnaphthalene itself does not react with the dinitro-sulphoxides, allhydroxy- and amino-derivatives which have been examined readilyform the 8-naphthyl derivatives. These possess well-defined tinc-torial properties, and when sulphonic groups are present thecompound is readily soluble in cold water j but the simple hydroxy-and amino-derivatives are sparingly soluble. Some of the chiefexamples of the S-naphthyl derivatives are described in the follow-ing table:Condensation of the pp-Dinitro-sulphoxide with Colour.a-Naphthylamine .............................8-Naphthylamine .............................a-Naphthol .......................................2-Naphthylamine-6 : 8-disnlphonic acid ..2-Naphthylainine-6-sulphonic acid......... Crimson ; , ,2-Naphthol-6 : 8-disulphonic ,, ......... Brown ; ,, violet in alkali.2-Naphthol-3 : 6-disulphonic ,, ......... Crimson ; ,,2.Naphthol-6-sulphonic , , ......... Olive green, violet in alkali.Purple ; sparingly soluble.Beddish-brown ; sparingly soluble.Blue ; sparingly soluble.Crimson ; solubleS-PHENYLPI-IENAZOTHIONIUM. PART 111. 373Attempts to purify and t o obtain these derivatives in thecrystalline state have been unsuccessful, since they persistentlyremain in the colloidal condition. The physical properties of thea-naphthol derivative are perhaps worth special mention.Afterundergoing a process of purification, this substance was finallyobtained as a blue, viscous jelly, which, on being broken by shock,exhibited a dry fracture.These S-aryl derivatives of phenazothionium are not formed byall aromatic compounds, the most prominent exceptions being thesimple nitro-derivatives of benzene and naphthalene. From ageneral point of view the reaction may be said t o be controlledby conditions similar to those observed in the process of sulphination(Trans., 1908, 93, 745), but hitherto the influence of the so-calledsteric conditions has not been observed. The resemblance betweenthese processes is not surprising, since the formation of the S-arylphenazothionium salts from the sulphoxides is evidently analogousto the third stage in the ordinary process of sulphination wherethe triaryl-sulphonium salt is formed from the sulphoxide.Finally, it is necessary to point out that the condensation ofthe thionyl group in the dinitro-sulphoxide is not confined solelyto aromatic compounds.For example, thiophen readily furnishesthe 8-thienyl derivative.S-Thien~llphenazothtionizsm.The condensation of thiophen with pp-dinitrodiphenylaminesulphoxide was effected in the usuaI manner; but since muchcharring takes place during the reaction, the reagents were employedonly in small quantity a t each operation, and the temperature waskept below 5O. The impure sulphate, obtained by pouring theunited reaction mixtures into water, was collected, washed firstwith water, and then with alcohol, and finally triturated withaqueous sodium carbonate. The impure base was collected, washed,and dried in the steam-oven. The dry product was crushed t o afine powder, and rapidly extracted with a little acetone to removesoluble impurities. The remaining product was crystallised fromboiling phenetole, which, on cooling, deposited dinitro-S-thienyt-phenazothionium hydroxide in large, led prisms, which exhibited asteel-blue lustre. The substance is very sparingly soluble in cordacetone, and does not melt below 250O:0.2032 gave 0.3828 CO, and 0.0330 H,O.C,,€I~0,N3S,,~H,0 requires C = 50.5 ; H = 2.6 per cent.From the analytical data it appears that the normal sulphoniumhydroxide has lost water during the recrystallisation from the highC=50.6; H=1%c c 374 DIXON AND TAYLOR : APPARATUS FOR DEMONSTRATINQboiling solvent; unfortunately the quantity of material was toosmall to enable the analysis to be repeated.I n conclusion, we desire to express our thanks to Dr. Cain forkindly lending us samples of the various amino- and hydroxy-sulphonic acids of naphthalene which were employed in this investi-gation. We also wish to thank the Research Fund Committee ofthe Society for a grant which has defrayed the expense of thisresearch.THE ORGANIC CHEMISTltY LABORATOKY,UNIVERSITY COLLEGE, LONDON