Indian Journal of ChemistryVol. 19A, October 1980, pp. 935-937

Electrophillc Addition of Chloramine & Dimethylchloramine toSulphur Dioxide & Oxidative Coupling of Sulphamide

by ChloramineHARI PRAKASH·

Inorganic Chemistry Division, National Chemical Laboratory, Poona 411 008and

HARRY H. SISLERGraduate School, University of Florida, Gainesville, Florida 32611

Received 17 December 1979; revised and accepted 10 March 1980

The addition of dimethylchloramine to sulphur dioxide is smooth and gives high yields of dimethyJsulphamoylchloride. A complex reaction of chloramine with sulphur dioxide occurs from which identification of sulphamoyl chlo-ride is made by derivatization to sulphamide. A major product of the chloramine-sulphur dioxide reaction is the ether-ate of hydrazodisulphamide postulated to be formed from the oxidative coupling of the by-product sulphamide viaH-atom abstraction by chloramine. The postulate is verified by the direct reaction of chloramine with sulphamide aIsuyielding the same etherate of hydrazodisulpbamide. Thus, oxidative coupling of non-aromatic diamides by ehlora-mide is demonstrated for the first time.

ELECTROPHILIC ionic and free radical addi-tions of N-chloramines following polarizationof the carbon-carbon multiple bond have been

demonstrated in earlier studies=". Electrophilicchloramination of unsaturated hydrocarbon substra-tes yielding ,B-chloroamines via the formation ofdialkylaminium and neutral dialkylamino radicals,subsequent polarization of the carbon-carbon multi-ple bond, followed by addition has also beenreported+". We wish to report on the addition ofchloramine and dimethylchloramine to an inorganicunsaturated substrate sulphur dioxide in which, inaddition to the lone pair electrons on sulphur atom,the S-O multiple bond can be polarized to act as asource of electrons for the electrophilic chloraminesto yield corresponding sulphamoyl chlorides inaccordance with Eqs (I) and (2).

NHzCI + S02 -+ H2NS02CI (1)

(CHs)2NCI + S02 -+ (CHa)2NS02CI (2)

We further report that like the oxidative couplingof phosphines and arsines, primary and secondaryphosphines and arsines, mercaptans and their seleniumanalogues, and aromatic phenols+w, chloramine caneffect the oxidative coupling of such non-aromaticdiamides as sulphamide according to Eq. (3).

2S0lNH2)2 + NH2CI --+ H2NS02NH-NHS02-

NHz + NH4Cl .. (3)

Materials and MethodsReaction of dimethylchloramine with sulphur

dioxide - A solution of dimethylchloramine (l00mmol) in CCl4 (loa ml) was cooled in an ice-Ht.Imixture and to this bath sulphur dioxide gas wasintroduced during 1.5 hr under anhydrous condition

with stirring. At the end of this period, the cold bathwas removed and the reaction mixture stirring over-night. Carbon tetrachloride was removed by distilla-tion under nitrogen and the thick oily residue distilledunder reduced pressure to give a liquid b.p. 80-81°/12-14 mm (b.p. reported+ for dimethylsulphamoylchloride, 71 °/12 mm), yield 109 (70 %), based ondimethylchloramine.

Preparation of the N, Nvdimethylsulphamide deriva-tive - Dimethylsulphamoyl chloride (69.3 mmol)prepared above was added dropwise to 30 % ammo-nium hydroxide (70 ml). The reaction mixture wascooled in an ice-bath. The white crystals were sepa-rated and recrystallized twice from water, washed withether and air-dried; yield of (CHa)2NS02NHz, 6.5 g(76%) based on (CHz)zNS02Cl; rn.p. 96°; m.p.96-96.5° (m.p. reported'> for [(CHa)2NS02NH297-98°)].

Reaction of ammonia-free chloramine with sulphurdioxide - In a typical experiment, a 300-ml three-necked round-bottomed flask with a magnetic stirrerwas attached to the vacuum manifold and evacuated.A solution of 57.6 mmol ammonia-free chloraminein diethyl ether (150 ml) was filtered hrough anhy-drous copper SUlphate into the reaction flask. Thestopcock between the fritted glass filter and the reac-tor flask was closed. The system was degassed.Sulphur dioxide (60.5 mmo!), dried over phosphoruspentoxide, was collected in a graduated tube andcondensed onto chloramine solution in the reactorflask. The reactor flask was cut off from the vacuumline and the reaction mixture allowed to stand for6 hr at _10° to -20°C with constant stirring. Thesolid fractions formed at the end of this period andthe 12-hr hold period of the ether filtrate were separa-ted, washed with ether, and dried in vacuo, combinedyield, 2.54 g. The solid fractions were recrystallized

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INDIAN J. CHEM., VOL. 19A, OCTOBER 1980

from dry ethyl acetate. The light brown ethyl acetateinsoluble solid was sublimed at 110° in high vacuum.The sublimate was identified as ammonium chloride;yield 0.8g. The pot residue did not exhibit any IRfrequencies of the S02 group in sulphones and sul-phonamides and remained uncharacterized. Theethyl acetate solution on cooling yielded white crys-talline solid which was repeatedly recrystallized fromabsolute ethanol. The solid was identified as etherateof hydrazodisulphamide, H~NS02NH-NHS02NH2'(CZH5),P; yield 0.2 g; m.p. 126-29°(d).

A repeat experiment was made by reacting 224 mmolsulphur dioxide with 105 mmol ammonia-free chlora-mine solution in diethyl ether (125 ml). After separat-ing ammonium chloride and etherate of hydrazodi-sulphamide (yield 0.4 g; m.p. 129-31°) from theinsoluble solid fractions, ether was evaporated fromthe filtrate. The brown residue was evacuated invacuo for several hours and weighed 1.5 g. Theresidue was taken in diethyl ether (150 ml) andammonolyzed. The light brown-coloured solid wasfiltered and recrystallized from ethyl acetate. Theethyl ecetate solution on cooling yielded white crys-tals identified as sulphamide, HzNS02NH2; yield:0.2 g-; m.p. 89-91° (lit.13 m.p. 91.5°) (Calc. forHzNS02NH2 : N, 29.16; S, 33.33. Found: N, 29.02;S, 31.40 %). The light brown solid insoluble in ethylaceta te was recrystallized from methanol and identi-fied as ammonium chloride; yield 0.5 g.

Reaction of sulphamide with ammonia-free chlora-mine - In a typical experiment, finely powderedsulphamide (25.50 mmol) was taken in a 500-mlthree-necked round-bottomed flask. The flask wasconnected to a vacuum manifold and evacuated for2 hr. Ammonia-free chloramine (69.38 mmol)solution in diethyl ether (250 ml) was first passedthrough a pad of anhydrous copper (II) sulphate andfiltered directly into the reactor flask. The flaskwas degassed. The contents were allowed to warmto room temperature and stirred for 80 hr. Thewhite solid was filtered under dry nitrogen atmos-phere and recrystallized from ethyl acetate. Theethyl acetate insoluble portion of the solid weighed3.12 g and was shown to be mostly ammonium chlo-ride by its IR and PMR spectra. The ethyl acetatesolution on cooling yielded white crystalline solid,identified as etherate of hydrazodisulphamide,HzNSOaNH-NHS02NHz. (C2H2h 0; m.p. 133-34°;yield 54.6 % based on sulphamide. Two other ethera-tes of hydrazodisulphamide (i) yield, 55.1 %; m.p.137-38° (d) (recrystallized from ethyl acetate followedby ethanol); and (ii) yield 26.2%; m.p. 131-32° (d)(purified from ethanol-ether) were also obtained fromrepeat runs.

Results and DiscussionThe addition of dimethylchlorarnine to sulphur

dioxide is smooth and gives high yields of dimethyl-sulphamoyl chloride. However, the reaction of chlora-mine with sulphur dioxide is complex and sulphamoylchloride could not be isolated. Its formation is infer-red by derivatization of an unresolved waxy productformed in substantial amounts to sulphamide byammonolysis which yielded sulphamide in approxi-mately 2 % yield. A large portion of chloramine

936

undergoes decomposition to ammonium chloridewhich accounts for the poor yield of sulphamoylchloride. A further reduction in the yield of sulpha-moyl chloride is caused by a secondary reaction inwhich ammonolysis of the initially formed sulpha-moyl chloride occurs to sulphamide which under-goes oxidative coupling by chloramine to givehydrazodisulphamide etherate, H2NS02NH-NHS02-NH2• (CZH5hO. The same etherate is formed in adirect reaction of sulphamide with chloramine indiethyl ether supporting the ammonolysis of initiallyformed sulphamoyl chloride to sulphamide; ammoniafor the ammonolysis reaction being produced ineither a disproportionation of chloramine to higherchloramines= or in the sulphur dioxide catalyzeddecomposition of chloramine--.

The formation of etherates in S02-NHzCl andS02(NHzkNH2Cl reactions is supported by theirelemental analyses, JR, PMR, and mass spectra.The IR spectrum of a typical etherate in KBr (vmaxin crrr") shows a very strong band at 3310 assignableto vNH2 of the sulphamide group. This assignmentfinds support from the observations recorded inIiteraturev?", The weak absorption at 1625 falls inthe region where NH deformations in primary andsecondary amines occur-". The relatively broad bandat 640 also corresponds to NH deformations of theNH2 group. The very strong peaks at 1350 and 1168observed in the IR spectra of the hydrazodisulpha-mide etherate have been assigned, based on literaturedatal6-18 to VasS02 and vsSOz respectively. Thebroad band of medinm intensity with maxima at510 and 525 may be assigned to the bending modesof SOz group. These bands usually appear as adoublet at 610-530 em:" and are attributed to bothrocking and bending modes of S02 groupI9,20. Thepeaks at 820 and 860 may be assigned to vS=N,based on the observations of Maschka and Aust'"and Moeller et a/22• The vN-N is difficult to locatedue to high symmetry of the N-N bond yielding bandof very weak intensity. This band can, however,gain sufficient intensity due to lowering of symmetryof the N-N bond as a result of intereactions withether. Thus, a very strong absorption at 985 with ashoulder at 940 in the etherate falls in the region ofN-N stretch. Nielsen and sisler23 have reported theN-N absorption in various hydrazino-phosphoruscompounds at --..950-996. The other readily identi-fiable bands of weak intensity at 3010 and 2950have been assigned to vCH of CH2 and CH3groups in ether; the 1460 and 1432 absorptions toCHa and CH2 deformations; and a strong absorptionin the region 1082-1108 to v-CH2-O-CH2- indethyl ether'".

The mass spectrum of the etherate shows theessential features of the hydrazodisulphamide struc-ture, initially fragmenting to the amidosulphoniumcation, H.NSOt (m/e 80) and the -NH-NH-species. The absence of mass species of 16 and 64corresponding to NH2 and SOz eliminates fragmenta-tion to NHz and S02 and strongly supports thecleavage to HaNSOt and -NH-NH- species.Thus, the observed mass species Nt (m]« 28), NH;t(m]« 17), NaH+ im]e 29), NH+ tm]e 15), and N3H+(m/e 43) can be accounted for as due to further frag-

HARI PRAKASH : ADDITION OF CHLORAMINE TO SULPHUR DIOXIDE

mentation of the -NH-NH- species. The highabundance of the mass species of 43 and 29 massunits is consistent with these peaks gaining enhance-ment of intensity from several fragments of diethylether and their recombination with the N2H2fragments. The peaks atm/e 27 and 61 are believed toarise from HCN+ and CaHsOt species, respecti-vely. A peak of weak intensity at m]e 149, remainsunassigned.

The PMR spectrum of the etherate taken in DMSO"de from internal sodium 3-(trimethylsilyl) propanesulphona te shows the NH2 and NR protons at -7.37and 4.92 ppm respectively as broad multiplets . inNH2/NH area ratio of 1.83 to 1 in reasonable agree-ment with hydrazodisulphamide. The CH3 and CR2

protons at.1.33 and 3.62 ppm respectively in the CH3/CH!l area ratio of 1.56 to I support theetherate for-mulations.

It must, however, be pointed out that ether ismysteriously bound in these adducts, affecting thecharacteristic quartet and triplet splittings. of themethylene and methyl protons which are observedas doublets. Although diethyl ether is released inaqueous solution of the etherate and identified on agas chromatograph and in the mass and IR spectraof etherates, its bonding is unusual and remainscuriosity.

AcknowledgementThis work was done at the University of Florida,

Gainesville, Florida, and Pratt Institute, Brooklyn,New York, USA.

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