Indian Journal of Engineering & Materials SciencesVol. 5, October 1998, pp. 334-338

Sulfonation of arylamine Part-5 : Preparation and thermal decompositionof di-m-chloroanilinium sulfate

Gurdip Singh=, Inder Pal Singh Kapoor & Jyotsna Singh

Department of Chemistry, University of Gorakhpur, Gorakhpur-273009, India

Received 25 March 1997; accepted 22 August 1997

White crystalline solid of di-m-chloroanilinium sulfate (di-m-CIAS) was obtained when m-chloroaniline andcone. sulfuric acid were mixed together in the ratio of 1:1 or 2: 1 at room temperature. Thermal decomposition ofdi-m-C1AS gave two isomeric chloroaminobenzenesulfonic acids (sulfonated products) and kinetics for the samewas evaluated using both isothermal and non-isothermal TG data. Di- m-C1AS seems to decompose by N-H bondheterolysis prior to sulfonation.

Sulfanilic and ring-substituted aminobenzene-sulfonic acids have been found to be of greatinterest from both mechanistic and preparativepoint of view. These find applications in organicsyntheses, dyestuffs', medicines, tanneries,detection of nitrous acids & bile pigments' andinhibit the coloration of fish oil'. In continuing ourstudies on the solid state sulfonation of ringsubstituted arylarnines't'" via intermediate saltformation, we have investigated the sulfonation ofm-chloroaniline. The reaction product of m-chloroaniline and cone. sulfuric acid in 2: 1 or 1:1molar ratio at room temperature was isolated andcharacterized as di-m-chloroanilinium sulfate (di-m-CIAS).

Thermal decomposition of di-m-CIAS wasundertaken by simultaneous TG-DTG, isothermalTG and DT A, since these studies are not yetreported in literature. The sulfonated products (m-chloroaminobenzenesulfonic acids) obtained byheating the salt at higher temperature undervacuum were characterised by elemental andspectral analysis.

Experimental Procedure.m-chloroaniline (Johnson purified by

distillation) cone. sulfuric acid (AR. Qualigens),silica gel G (TLC grade, Qualigens) and bariumchloride (BDH) were used as received.

Preparation and characterization of di-m-chloroanilinium sulfate (di-m- CIAS)-Whiteamorphous precipitates of di-m-CIAS wereobtained immediately at room temperature (RT)when m-chloroaniline mixed with cone. sulfuricacid in 2:1 (y = 64%) or 1:1 (y = 82%) molar ratioas shown in Scheme I.

The precipitates were washed repeatedly withn-butanol. and then recrystallised from mixture ofdimethylsulfoxide and dimethylformamide (1: I) inorder to remove unreacted m-chloroaniline andother impurities. White long transparent needleshaped crystals were obtained on keeping theabove solution for 48 hrs at room temperature. Thepurity of the salt was checked by TLC(chloroform: methanol and iodine Rf = 0.92). Thesalt was quite stable at room temperature and wasfound to decompose (d 212°C) without melting. Itwas identified as di-m- CIAS by elementalgravimetric (sulfur estimation using BaCh) andspectroscopicll-14 analysis. IR spectra were takenon Perkin-Elmer, UV on Hitachi-U-2000 and IH_

Scheme 1

SINGH et a/.: SULFONATION OF ARYLAMINE

NMR on Varian EM-360, \3C-NMR on VM-400and MS on Joel-SX-120 (FAB) spectrometers.

Thermal decomposition studies on di-m-CIAS- Thermal decomposition on di-m-ClAS wasstudied using the following techniques:

Simultaneous TG-DTG-Simultaneous TG-DTG on di-m-CIAS (wt.IOmg, 200-400 mesh)was undertaken at a heating rate of 10°C/min.under a controlled dynamic atmosphere of nitrogen(45 mL/min) on Dupont 990 Modular thermalanalysis system in conjunction with 951thermogravimetric analyser and thormograms arereported in Fig.l.

Non-isothermal TG-TG studies on di-m-CIAS(wt. 10mg, 200-400 mesh) were undertaken instatic air at a heating rate of 2°C/min using anindegeneously fabricated apparatus" fitted withtemperature indicator cum controller (Model CT808T Century) and bucket type platinum crucible(h = 10mm, dia = 10mm). Fraction decomposed(a) vs temperature eC) plot is given in Fig. 2.

Isothermal TG-Isothermal TG on di-m-CIAS(wt. 10mg, 200-400 mesh) was carried out in static ~air at temperatures 85, 195,205,215 and 230°C by iindegeneously fabricated TG apparatus and a tversus time (t) plots are reported in Fig.3a. ¥

DTA-DTA (Perkin Elmer) on di-m-CIAS was ~carried out in static air using 10mg (200-400 ~mesh) of sample at a heating rate of 10°C/min. The k:thermogram (Fig.4) was recorded using a twopenpotentiometric strip chart recorder.

Conversion of di-m-CIAS to isomeric chloro-

80'II 1·0

a/11;u

o·s <

,:

.-ne

().O

F -o·s90

"0

• 110§.Eou!40

Eo~------~~------..h~====~o ]00 600T.IfII*Otu,..:c

Fig. I-Simultaneous TG -- DTG curve for di--m--ClAS in inertatmosphere

335

aminobenzenesulfonic acids (CIABSA)-1.5 g ofdi-m-CIAS was heated in a tube furnace" at255±2°C for lh under reduced pressure (60 mmHg) and violet coloured mixture was obtained.TLC (chloroform: gle. acetic acid: abs. ale. 4: 1: 1)of this mixture using iodine showed three spots (Rr= 0.71, 0040 & 0.22). Unsulfonated m-chloroaniline (Rf = 0.71) was confirmed by Co-TLC using authentic sample. Doubly distilledwater (200mI) and activated charcoal were addedto the above heated sample and solution washeated to incipient boiling for 10 minutes. Twocompounds (Fractions 1 & 2) were separated outfrom the solution on cooling the solution to roomtemperature .

0·2

0·]

0·4

o·s _

0'6

0·7

0-"40 100 160 220 280 140

T.m~ratur.·C400

Fig.2- TG curves for di-m--ClAS in static air

o-s a,_ 2']0 Cb Q 215°e

0'4 ,. 2Os:e'I!. d,.I95 e"0 .," 185°ei 0·']

E3 0·2~

.J..-...•...-+-- •..d

~ __ --a@

~')-- 't!r'- b~..--.u--c

16 14 n 24 48 56 64Tim. ,min

72

Fig.3 (a)-Isothermal TG curve for di--m--ClAS in static air

336 INDIAN 1. ENG. MATER. set, OCTOBER 1998

Results and DiscussionDi-m-'CIAS was found to be formed when m-

chloroaniline was reacted with cone, H2S0

4• TO Condensed ohoset t lt)

curve reported in Fig.f(Part A4B) showed that t>.,3 t Sulln

di-m-'ClAS (I) decompose in solid state by proton CI Cl CI

fi 4-1015-22 . -@- <Q- @-trans er' process (Scheme 2) via an i tactivatedcomplex(II)tofonnm-chloroanilineand H03S 0 NH2+ 0 NH2+ 0 NH2 + H2

0

sulfuric acid molecules in condensed phase(IIl). A S03H

weight loss of 40.7% (theor. 41.2%) was observed (tv) (V)

in the temperature range 110-230°C which proves --------the evolution of water and m-chloroaniline from PT- Proton transfer, Sulln - Sulfonation

di-m-'CIAS (step 3}. It seems that chloroarnino- Scheme 2benzenesulfonic acids are fo~ed by C-sulfonationat higher temperatures.

Fraction No.1 [2-chlor0-4-aminobenzene-sulfonic acid, 2-'C1-4- NH2C6H3S03H(IV)]

TLC (R, = 0.40, chloroform : acetic acid, abs.ale., 1.5 : 0.5 : 0.8) d 310°C, found C 35.16, H3.18, N 6.6, S 15.41% Cal. for C6~03NCIS, C34.62, H 2.89, N 6.73, S 15.39; UV "'max. (H20cone. 0.01%) 332.6 (0.06), 298.4 (1.08), 240.8(2.62) and 208.8(L24)nm; MS mle (relativeintensity), 127 (100%), 208(35.9), 190(35.8),137(30.1), 129(30.6), 125(27.3), 100(17.1),93(79.0), 92(21.0), 90(19.0), 66(35.0), 65(43.0),63(28.0), 59(21.0).' 44(76.0), 42( 14.0); IR(KBr)

Fraction No. 1 & 2 were identified as isomericchloroaminobenzenesulfonic acids(2-chlor0-4-aminobenzenesulfonic acid IV and 2-amin0-4-chlorobenzene-sulfonic acid V) by microanalysis,sulfur estimation (Carious method) andspectroscopy.

Cross-sulfonation studies-m-chloroaniline,two isomeric chloroaminobenzenesulfonic acidsand sulfanilic acid were found to be formed whendi-m-'CIAS was heated with aniline at 255 ± 2°Cunder reduced pressure (60 mm Hg) for 40 min.The products obtained were confirmed by Co- TLCusing authentic samples. The thennoanalytical datafor thermal decomposition of di-m-CIAS are givenin Table I.

Table 1-Thennoanalyticat data for thermaldecomposition of di-m-CIAS

DTAEndotherm

eC)

TG(wt. loss %)

DTGPeak

temperatureeC)

(Theor)41.22

(Obs)40.70 215

354209356

CI

@-tH, 561 N'H, <ss<Cl

Di-m-CIAS(I)

J1",

["©-~","~0' - 50,-0'.c H- N'~, JActivated complex (11)

1400 - 1410(vc -CI sym), 1160-1190 (VC-C1 asym),3340-3450 b, 3040 - 3150 b, 2850 b, 2600 m.(VNH), 1550m(~), 1250m (VC-N), 1027-1046 b,(VS04-2 sym), 1292 (VS04-2 asym), 1480s, 882s,S20s(vc~), S52w, 646w, 71Sw (vc-s); 'H-NMR(DMSO-D6) 6.2-8. 1(pentate 3H) aromatic, 3.8-4.9(NH\), \3C (CDCh) s = 13S.3,· 135.1, 133.9,129.2, 122.5, 119.9(6s).

Fraction No.2 [2-amin0-4-chlorobenzene-sulfonic acid, 2-NH2-4-'C1 C6H3S03H (V)]; TLC(Rf 0.22, chloroform : glc. acetic acid : abs. alc.,1.5 : 0.5 : O.S)d 317°C found, C 33.9, H 2.54, N5.75, SI5.15%) Calc. for C6H603NSCI,C 34.62, H2.S9, N 6.73, S 15.39; UV Amax (H20 cone 0.01%),297.6(0.9S), 239.6(2.5), 216.4 (3.54) nm : MS mlerelative intensity 190(100 %), 210(33.8).208(90.9), 192(38.1), 173(24.0), 127(39.7),93(15.1), 44(18.0); IR(KBr), 1397-1410 (VC-CI

sym] 1167-1182 (VC-CI asym), 3335-3450b,3040-3150b, 2850b, 2560b-2640b (VNH); 1550m (cS NH), 1240 s (VC-N), 1020-1045b (V S04-2 sym),

SINGH et al.: SULFONATION OF ARYLAMfNE

1290, CS04-2 asym ), 1480 s, 820 s (vc-c), 715w,642w, 549 (vc-s); IH-NMR (DMSO-D6), 5.7-7.7 e 18S·C

• 195·C(multiplate, 3H aromatic) 3.0-5.0 (-NW3),"''Il • :lostI3C(CDCh) 0 = 138.5, 135.0, 1340, 129.2, 122.2, •.•: to :lISOC119.8 (6s). j 015o 730°C

oC>.Cross-sulfonation studies confirmed beyond ~

doubt the occurrence of proton transfer ( N-H ~bond heterQ!ysis)17-22in the decomposition of di-m :.CtAS. Molecular ion peak at mle 208 also confirms 0·05

(IV) & (V). Water was confirmed by Karl-Fischerreagent" and m-chloroaniline by chemical andreagent'" and m-cl)loroaniline by chemical andchloroaniline was found to be superimposable with Fig.3 (b}-Klhdic analysis of di-m-CIAS by the Parabolicreported data'!' 24. law

A plateau in the temperature range 220 - 290°C(Fig. 1 part B~C) indicates the stability ofClABSA. Further heating (> 300°C Fig. 1, inertatmosphere) resulted in the decomposition of ElCO

ClABSA leaving carbonaceous residue (Fig. 1, fPart C~D~E) . I peak both in DTG (Fig. 1) and AT

DTA (Fig. 4) seems to be due to sulfonation 1process and II peak due to decomposition ofClABSA.

The kinetics of the thermal decomposition of di-m-CIAS was evaluated by both non-isothermoland isothermal TG data. Non - isothermal TG datawas fitted in Mac Callum Tanner equation(MCT)8,25,27(Eq. 1) and values of E, are reported inTabh;2.

In g (a) = In E. I;R - 0.485 E. (0.435)

_ 0.449 + 0.217 x 10 3

T

1 (1 t:where, g '(a) = - - a1- n

for n=O ,112, 2/3 and for n = 1, g(a.) = -In(1-a).and cp=heating rate, Ea = activation energy fordecomposition and n = order parameter.

The kinetics of the thermal decomposition of di-m-CIAS was also evaluated from isothermal TG

.. , (1)

~HOO

0·7).---------------------:--.

Q

o

o.oIIdM~:::;::.~~-_:_':_ '8 16 24 12 40

TiI'JW, min56

337

64 77

500

data using Parabolic law27-29(Eq. 2) and plots aregiven in Fig. 3 b .

0.2 = k t ... (2)

E, values estimated using MCT & Parabolic law(Table I) are nearly the same. However E; for di-m-CIAS has been found less as compared todianilinium sulfate (28.27 kcal/mol) and di-p-chloroanilinium sulfate (21.25 kcal/mol). This maybe due to the strong inductive (-I) effect of m-CIgroup which may cause weakening of N-H bondand consequently proton transfer is favoured.

Temp( K)458468478488503

100 700 lOOT.m~rotur. :C

400

Fig.4--DTA curve for di-m-CIAS in air

Table 2-Kinetic parameters for thermal decomposition of di-m-CIAS

MacCallum Tanner Eq.Order parameter

n=On=1

n = 112n =213

E.(kcal/mol)

11.8711.9111.1512.13

Parabolic LawRate constant (I0-J/min)

0.901.52.52.83.2

B;.(kcal/mol)

)1.95

338 INDIAN J. ENG. MATER. SCI., OCTOBER 1998

ConclusionsSolid state decomposition of di-m-CIAS

involves proton transfer (unimolecular elementaryreaction) process as a primary step and 2-chloro-4-amino-(IV) and 2-amino-4-chlorobenzene-sulfonic acid (V) were found to be the sulfonatedproducts.

AcknowledgmentsWe thank Head of Chemistry Department,

Gorakhpur University Gorakhpur for laboratoryfacilities. Thanks are also due to VSSC,Trivandrum for TG-DTG, Dr. K. D. S. Yadav,Chemistry Department, Gorakhpur UniversityGorakhpur for UV spectra & Dr. Saroj ShuklaDelhi University for DTA. Authors are thankful toCDRI, Lucknow for spectral data and CSIR, NewDelhi for financial assistance to one of the author(lPSK).

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