determination of thiosemicarbazide alone and in its metal ... · microchemical journal 28,374-391...

MICROCHEMICAL JOURNAL 28,374-391 (1983)

Determination of Thiosemicarbazide Alone and in Its Metal Complexes with Arylhalosulfonamides

B. THIMME GOWDA*P* AND D. S. MAHADEVAPPA?

*Department of Chemistry, Hydrocarbon Research Institute, University of Southern California, Los Angeles, California 90089-1661, and tDepartment of Chemistry, Manasa

Gangotri, University of Mysore, Mysore-570006, Karnataka, India

Received March 15, 1982

INTRODUCTION

Thiosemicarbazide (TSC) and its derivatives are well known as metal complexing agents and find application in the characterization of alde- hydes, ketones, and polysaccharides. They are antitubercular active and are found to be active against influenza, protozoa, small pox, and certain kinds of tumor. They have also been suggested as possible pesticides and fungicides. Their activity has been due to their ability to chelate trace metals. These facts have led recently to an increased interest in the chemistry of transition metal chelates of thiosemicarbazides (2, 8, 20, 21). Since a number of metal complexes of the compound are known, suitable analytical techniques are essential for estimating TSC in the pure state as well as in its complexes. The analytical procedures reported so far for its estimation are based on its oxidation by alkali metal hypohalites (29), lead tetraacetate (23), and some of the arylhalosulfonamides (14, 30). Although on different occasions we have employed some of the arylhalosulfonamides individually for determining number of industrially and biologically important inorganic and organic compounds (14, 30), general procedures for estimating thiosemicarbazide in solution either in the pure state or in its metal complexes with these oxidants are lacking. In the present investigations as a part of our broad program of developing sensitive analytical techniques for estimating number of compounds in solution, the behavior of arylhalosulfonamides as oxidimetric analytical reagents toward TSC, alone and in its metal complexes has been critically examined and general procedures for its determination have been de- vised.

TSC (L) and its following complexes were considered for that purpose.

ZnL2S04 NiL$SOd -3H20 PdLzClz cis-PtLzCll ZnL*Cl* NiUNQh PdL2Br2 trans-PtLzC12

1 To whom all correspondence should be addressed. Present address: Department of Chemistry, Mangalore University, Mangala Gangothri-574 152, Mangalore, Karnataka, India.

374 0026-265X/83 $1.50 Copyright 0 1983 by Academic Press, Inc. ~11 rights of reproduction in any form reserved.

DETERMINATION OF THIOSEMICARBAZIDES 375

ZnMNW2 NiL2Cl2 PdL212 PtL2Br2 ZnL2(ClO4)2 Ni(L-H)z PdL2(NCS)2 PtL21, CdL2S04 cis-PdL2(N03)2 PtL,(CNh CdL2C12 rrans-PdL2(N0& PtL2(NCS)2 WA% Pd(L-H)2 PtL2(NW2

Pt(L-H),

L = NHzNHCSNH2 and L-H = NHzNCSNH2. The chemistry of iV-halo-N-sodio (or potassio) and N,N-dihaloaromatic

sulfonamides

CH3-- 0 0 !I -a-N<

M(or X)

(or H) 0 x

where M = Na or K, X = Cl,Br, or I has evinced considerable interest as they are sources of halonium cations, hypohalite species, and N-anions which act as both bases and nucleophiles. As a result they interact with a wide range of functional groups in aqueous, partially aqueous, and nonaqueous media in the presence of acids or alkalies, effecting an array of molecular transformations. Generally monohaloamines undergo a two- electron change while dihaloamines are four-electron oxidants. The re- duction products are the respective sulfonamide and MX or HX. Al- though the toluene analogs of haloamines are well known, there is little information about the derivatives of benzene. The oxidants considered in the present investigation are:

1. N - Chloro - N - sodio - p - toluenesulfonamide, p-CH3- C6H,$02NClNa, well known as chloramine-T (CAT, RNClNa, where R = P-CH~C~H.,SO~ -).

2. N,N - Dichloro - p - toluenesulfonamide, known as dichloramine-T (DCT, RNC12).

3. N - Bromo - N - sodio - p - toluenesulfonamide, bromamine-T (BAT, RNBrNa).

4. N,N - Dibromo - p - toluenesulfonamide, dibromamine-T (DBT, RNBr2).

5. N - Iodo - N - potassio - p - toluenesulfonamide, iodamine-T (IAT, RNIK).

6. N - Chloro - N - sodiobenzenesulfonamide or chloramine-B (CAB, R’NClNa, where R’ = C6H5S02-).

7. N,N-Dichlorobenzenesulfonamide or dichloramine-B (DCB, R’NC12). 8. N - Bromo - N - sodiobenzenesulfonamide or bromamine-B (BAB,

R’ NBrNa). 9. N, N-Dibromobenzenesulfonamide or dibromamine-B (DBB,

R’NBr2). 10. N - Iodo - N - potassiobenzenesulfonamide, iodamine-B (IAB,

R’NIK).

376 GOWDA AND MAHADEVAPPA

The chemistry of chloramine-T has been better established than the remaining oxidants. Recently Campbell and Johnson (9) have reviewed the existing literature on CAT and related compounds. The redox poten- tial of CAT/RNHz is pH dependent and decreases with increase in pH of the medium and has values of 1.14 V at pH 0.65 and 0.5 V at pH 12. Depending on the pH of the medium CAT furnishes different types of reactive species in solution (6, 15, 17, 18, 23, 33) such as N - chloro - p - toluenesulfonamide (monochloramine-T, RNHCI), dichloramine-T (RN(&), HOCl, and possibly HzOCl’ in acid solutions, and RNCl- and OCl- ions in alkaline medium. Free chlorine has also been detected in acid medium in the presence of chloride ion (15, 32).

EXPERIMENTAL

Thiosemicarbazide (E. Merck, Darmstadt) was purified by recrystalli- zation from the aqueous solution of the sample. PdC12 and H,PtCl, . xH20 (Johnson Matthey Ltd., London) were used for preparing the Pd(I1) and Pt(I1) complexes. All other materials and reagents used were of Analar grade. Triple-distilled water was used for preparing all the solutions. Ul- traviolet spectra were obtained from a Beckmann DB spectrophotometer. Infrared spectra (KBr disk) were recorded on a Carl Zeiss UR-10 infrared spectrophotometer.

Preparation of Complexes

Thiosemicarbazide complexes of zinc, cadmium, mercury, nickel, platinum, and palladium were prepared as follows (13, 14, 20, 21).

ZnL*Clz and NiL$lz were prepared by evaporating aqueous mixtures containing stoichiometric amounts of TSC and the corresponding metal chloride. Complexes ZnL2(N0&, ZnL2(C104)2, CdL&$, HgL&&, and NiL*(NO& were prepared by mixing aqueous solutions of TSC and the corresponding metal salts in the molar ratio 2: 1. The resulting solutions were slowly evaporated at 60°C on a water bath and then cooled in ice, when the crystals of the complexes appeared. Crystals of ZnL$OA and CdL$S04 were obtained by simply scratching the sides of the beaker containing the aqueous mixture of TSC and metal sulfate in the stoichiometric ratio, while NiL$S04 * 3H20 was crystallized as pinkish violet nee- dles when the concentrated aqueous mixture was kept in a desiccator for 2-3 hr. The neutral complex Ni(L-H)* was obtained by the direct interaction of NiC12 * 6H20 and TSC in aqueous ammonia in a 1:2 molar ratio.

cis-PtL& was prepared by mixing HzPtCl, . xHz0 and TSC in hot ethanol in slightly beyond I:2 molar ratio, while the trans compound was obtained by mixing the reactants in cold condition. cis-PtLz(NO&, trans- PtL2Br2, trans-PtL&, tram-PtLz(CN)l, and tram-PtLz(CNS)z were pre-


pared by anion substitution, by adding stoichiometric amounts of saturated aqueous solutions of the respective nitrate (or 1: 1 HN03) or halide or cyanide or thiocyanate to an ice-cold saturated aqueous solution of cis-PtLzCl;?. trans-PdLzClz was prepared by mixing PdClz and the ligand in 1:2 mole ratio in 2 M HCl. trans-PdLz(NO&, trans-PdLzBrz, trans- PdL&, cis-PdLz(CN)z, and cis-PdLz(CNS)z were prepared by methods similar to those of the corresponding platinum complexes. ciS-PdLz(NO& was precipitated by mixing Pd(OH)z and TSC (in a 1:2 mole ratio) in I:1 HN03 at 60-70°C. The neutral complexes, tram-Pt(GH)z and trans-Pd(G H)z, were prepared respectively by the addition of 1 M ammonia to aqueous solutions of the corresponding chloride complex.

The complexes were recrystallized from aqueous solution and their composition was checked by elemental analyses (Table 1). The complexes were further characterized by recording their Ir spectra. A typical set of spectra and its assignment are shown in Table 2 (20, 21).

The nature of metal-ligand bonding in the complexes was established by comparing their ir spectra with the spectrum of TX. The N-H stretching frequencies around 3000 cm- ’ in TSC are affected by complex

TABLE 1

ELEMENTALANALYSESOFTHECOMPLEXES

Complex

%M %S %N %X

Calcd Found Calcd Found Calcd Found Calcd Found

ZnL#04 19.0 18.8

ZnLO’03)2 17.5 17.7

ZnL2U04)2 14.6 14.7

CdLQ 30.7 31.0

CdL$04 28.8 28.5

H&C12 44.2 44.8 trans-PdL2C12 29.8 29.6 trans-PdL2Brz 23.7 23.9 trans-PdL212 19.6 19.5 cis-PdLz(CNS)z 26.3 26.2

cis-PdL2(N03)z 25.4 26.0

rrans-PdLz(NO& 25.8 25.4 Ivans-Pd(L-H)z 37.1 36.9 cis-PtL2Cl2 43.5 43.3 Wans-PtL2Cl2 43.5 43.6 trans-PtLlBrz 36.3 36.9 Wans-PtL212 30.9 30.7 tram-PtLz(CN)l 45.4 45.8 rrans-PtLz(CNS)z 39.5 40.0 CiS-PtLz(NO3)2 38.9 38.7 trans-Pt(L-H)2 52.0 51.2

28.0 27.9 24.4 24.3 - -

17.2 17.4 30.1 30.6 - - 14.3 14.0 18.8 19.1 - -

17.5 17.0 23.0 23.2 - -

24.6 24.3 21.5 21.3 - - 14.1 13.9 18.5 18.4 - -

17.8 17.3 23.4 22.9 19.7 19.8

14.3 14.7 18.7 18.5 35.6 35.1 Il.8 11.9 15.5 15.5 46.8 47.1 31.7 32.0 27.7 27.5 28.7 28.2

15.5 15.3 27.2 26.5 - -

15.5 15.5 27.2 26.7 - - 22.4 22.7 29.4 29.2 - - 14.3 14.4 18.7 18.6 15.8 15.8

14.3 14.4 18.7 19.0 15.8 15.7 11.9 12.1 15.6 16.1 29.8 29.5 10.2 9.9 13.3 13.5 40.2 40.6

14.9 14.7 26.1 26.1 12.1 12.0 26.0 26.2 22.7 22.8 23.5 23.1 12.7 13.0 22.4 22.5 - -

17.1 16.9 22.5 22.2 - -


formation. Further, the strong band at 800 cm ’ in TSC attributed to C = S stretch shifts to lower regions by as much as 100 cm-’ in the complexes. It is likely that the metal ion coordinates through both the nitrogen atom of the hydrazinic residue and the sulfur atom of the ligand.

The cis and tram isomers among the complexes were classified by the differences in their ir spectra (21). X-Ray diffraction studies showed that; due to absence of symmetry, the cis form shows more lines than the tram form (21).

Preparation of Oxidants

Chloramine-T. CAT (E. Merck) was purified by the method of Morris et al. (23).

Dichloramine-T. DCT was prepared by the chlorination of CAT solutions (19). Pure chlorine was bubbled through the aqueous solution of CAT for about 3 hr. The fine white precipitate formed was filtered off, dried on the filter paper by sucking dry air through it, and then dried in a blackened vacuum desiccator for 24 h.

Dibromamine-T. DBT was prepared by the bromination of chloramine- T (CAT) solutions (24). About 4 ml of liquid bromine was added dropwise from a microburet to a solution of -20 g of CAT in 400 ml of water with constant stirring of the solution at room temperature. DBT separated out was filtered under suction, washed thoroughly with water until all the bromine adsorbed on the compound was completely eliminated, and then dried in a vacuum desiccator for 24 h.

Bromamine-T. BAT was obtained by dissolving DBT in 4 M NaOH (25). About 20 g of DBT was dissolved with stirring in -30 ml of 4 M NaOH at room temperature and the resultant aqueous solution was cooled in ice. Pale yellow crystals of BAT formed was filtered under suction, washed quickly with the minimum quantity of cold water, and dried over phosphorus pentoxide.

Zodamine-T. IAT was prepared by the iodination of p-toluenesulfonamide (28). A solution of p-toluenesulfonamide (4.5 g) in the minimum quantity of 10% aqueous potassium hydroxide solution is slowly added to a small excess of iodine solution (9 g of iodine and 18 g of potassium iodide in 20 ml of water). The triiodide crystallizes out. Potassium hydroxide solution (50%) is added dropwise until the solid is taken up and iodamine-T then separated as a yellow crystalline powder. It is collected, quickly washed with cold saturated potassium chloride solution, pressed between filter papers, and dried over phosphorus pentoxide. It is recrystallized from hot water.

Chloramine-B. CAB was obtained by the partial chlorination of benzenesulfonamide (IO). Pure chlorine was bubbled through a solution of

TABL

E 2

A TY

PICA

L SE

T O

F IN

FRAR

ED

SPEC

TRA

OF

TSC

AND

ITS

MET

AL

COM

PLEX

ES

TSC(

L)

cis-

PtL2

Cl2

tmns

-

PdLz

Clz

tram

- Pt

(L-H

)2

ZnLz

S04

WAC

12

Assig

nmen

t

3389

(s

)

3285

(m

) 31

94

(m)

1642

(s

)

1623

(s

) 15

31

(s)

1487

(m

)

1326

(m

)

1290

(s

)

1172

(s

)

1000

(s

) 81

9 (s

) 65

0 (s

) 50

4 (s

)

3355

(w)

3262

(w)

3150

(m

) 16

46

(vs)

1578

(V

W)

1454

14

00

(m)

1 (m

)

1324

(vw)

12

67

(w)

1218

(m

) 11

58

(w)

1025

(V

W)

700

(m)

641

(m)

481

(VW

)

3354

(m

) 32

48

(m)

3142

(w

) 16

48

(s)

1621

(s

) 1

1580

(V

W)

(4

1450

(s

) 14

04

(w)

1384

(m

)

1342

(m

) 12

39

(s)

1158

(m

) 10

17

(VW

) 70

0 (s

)

621

(s)(b

) 49

8(vw

) 43

1 (m

)

3446

(m

) 33

75(w

) 32

25

(w)

Cd)

16

50

1605

(s

) 1

(s)

1533

(w

) 14

33

(w)

(4

1345

13

17

(s) 1

(s

) 12

75

(m)

1240

(s)

1146

(s

)

947

(vs)

71

2 (s

) 67

3 (m

)

512

(w)

494

(s)

446

(s)

Cd)

(4

3372

(m

)

3313

(m

) 31

76

(m)

1655

(s

)

1636

(s

) 15

66

(s)

1434

(m

)

1415

(m

)

1321

(m

)

1115

(s

)(b)

996

(m)

713

(s)

623

(s)

602

(s)

3400

(s

) 32

93

(w)

2936

(w)

1665

16

22

(s) I

(s

) 15

70

(s)

1467

(s

) 13

88

(m)

1336

(m

)

1189

(m

)

1003

(s

) 63

4 (s

) 54

4 (s

)

494

(m)

VNH

2

VNH2

VNH2

aNH2

PNH

and

TN

UCN

* aN

H2

+ "C

S 41

PNH~

~NH?

an

d PN

H~

vcs

Skel

etal

vib

ratio

ns

Nore

. vs

: ve

ry st

rong

; s:

st

rong

; m

: m

ediu

m;

w:

weak

; VW

: ve

ry we

ak;

d:

doub

let;

b:

broa

d;

u:

stre

tchi

ng;

a:

defo

rmat

ion

or

bend

ing;

p:

rock

ing.


benzenesulfonamide in 4 M NaOH for 1 hr at 70°C. The precipitated CAB was filtered, washed, dried, and recrystallized from water.

Dichloramine-B. DCB was prepared by the chlorination of CAB (38). The procedure is similar to that for DCT.

Dibromamine-B. DBB was obtained by the bromination of CAB (22) by a method analogous to that for DBT.

Bromamine-B. BAB was prepared by the partial debromination of DBB (2). The latter (31.5 g) was added in small quantities at a time and with constant stirring to 50 ml of 4 M NaOH. The solution was cooled in ice. The crystals formed were filtered under suction and dried over anhydrous calcium chloride. The compound was recrystallized from hot water (50°C).

Zodumine-B. IAB was obtained by a method (28, 32) similar to IAT but using benzenesulfonamide instead of p-toluenesulfonamide.

The purity of all the oxidants was checked by estimating, iodometri- tally, the amounts of active halogen present in them and the oxidants were further characterized by their ir spectra (recorded on a Perkin- Elmer 298 grating infrared spectrophotometer) and Fourier transform ‘H- and 13C-NMR spectra (obtained on a Bruker WH 270-MHz nuclear mag- netic resonance spectrometer, using TMS as the internal standard). Typ- ical sets of spectra and their assignment are shown in Tables 3 and 4 (3- 5, 7, 26, 27, 35).

Approximately decinormal solutions of the monohalosulfonamides (except IAT and IAB) were prepared by dissolving requisite amounts of the solids in triple-distilled water. IAT and IAB were dissolved in 0.1 N potassium hydroxide solution. Solutions of dihalosulfonamides were pre-

TABLE 3 TYPICAL INFRARED SPECTRAL DATA(NOTTHE COMPLETE SPECTRA)• F SOME OFTHE

AROMATIC HALOSULFONAMIDES

BAT

615 (m) 665 (m)

915 (s) 1015 (m) 1075 (m) 1120 (s) 1235 (s) 2150 (w)

DCB

538 563

580

1180 (s) 1340 (s)

BAB DBB Assignment

561 558 Out of plane ring 578

(s) I (s) (4 582

(s) I (s) (4 deformation

VN-Br

934 (s) 995 (w) V%N 1044 (w) 1020 (w) in plane (Y~H 1106 (s) 1083 (m) in plane act 1150 (s) 1178 (vs) vs SO2 1262 (vs) 1363 (vs) vas SO2 1450 (s) 1408 (w) w=c 1489 (w) 1452 (s) w=c 1653 (s) 1582 (m) vc=c

Note. vs: very strong; s: strong; m: medium; w: weak; Y: stretching; a: in plane bending or deformation.


TABLE 4 FOURIER TRANSFORM IH AND 13C NMR SPECTRAL DATA OF

AROMATIC HALOSULFONAMIDES 4

Compound J o.ma

2,6 335 4 -CH, (Hz)

PTSb 1.93 (d) CAT 7.71 (d) DCT 8.00 (d) BAT 7.80 (d) DBT 8.01 (d) CAB 7.86 (d) DCB 8.14 (d) DBB 8.15 (d)

CAT 145.24 DCT 147.81 BAT 145.39 DBT 147.04 CAB 142.48 DCB 136.16 BAB 143.38 DBB 143.29

C-l

‘H spectra: @relative to TMS) 7.44 (d) - 2.42 (s) 7.37 (d) - 2.38 (s) 7.48 (d) - 2.53 (s) 7.40 (d) - 2.40 (s) 7.46 (d) - 2.52 (s) 7.72 (m) - - 7.86 (m) 7.63 (m) 1.81 (m) 7.67 (m) -

c-4 C-2,6

13C Spectra (ppm relative to TMS) 139.44 131.69 126.27 131.60 140.50 131.75 126.86 131.41 134.39 131.26 129.09 131.38 134.30 131.26 126.21 132.90

c-3,5 Methyl C

129.52 131.02 129.40 129.86 129.37 129.37 129.31 129.49

8.35 8.00 8.00 8.00 8.00 8.00 8.00 8.00

23.0 22.2 23.0 22.2 -

- -

0 Coupling constant. b para-Toluenesulfonamide; s: singlet; d: doublet; m: multiplet

pared in water-free acetic acid (glacial acetic acid containing 10% v/v acetic anhydride). All the solutions were standardized iodometrically and stored in amber-colored bottles.

The following buffer solutions were prepared as per standard methods (12): pH 1 and 2 (HCl + KCl); pH 3 (citric acid + NazHPOJ; pH 4-6 (acetic acid + sodium acetate); pH 7-9 (borax + boric acid + NaCl); pH 10 (NaHCOs + Na&03).

Solutions (-2 mg/ml) of TSC and its complexes were prepared in triple- distilled water or acid solutions of various concentrations or buffer solutions of pH I-10 or alkali solutions of different concentrations.

Preliminary Studies

Known quantities of the reductant solutions were added to known excessive volumes of the oxidants in separate iodine flasks (only aqueous


solutions of the reductants were used with the dihalosulfonamides, i.e., DCT, DBT, DCB, and DBB). The reaction mixtures were set aside for various intervals of time at room temperature (-300°K) with occasional shaking. The excess of oxidant (CAT, DCT, BAT, DBT, CAB, DCB, BAB, or DCB) in each flask left unconsumed was iodometrically deter- mined by back titration with standard thiosulfate.

It was observed that with monochlorosulfonamides (CAT and CAB) the oxidation of TSC is fast in the pH range 1-5 (fastest in pH 4) and slow in the alkaline solutions. The twelve-electron stoichiometric oxidation of pure TSC takes place in less than 30 min in 0.1 N mineral acid solutions and buffer solutions of pH 1-5. The stoichiometric oxidation of complexes was complete within 15 min. The oxidation of TSC and its metal complexes by monobromosulfonamides (BAT and BAB) is sluggish in acid solutions and in buffer solutions of pH l-10 but is rapid in alkaline solutions. The twelve-electron stoichiometry per TSC molecule was noticed in 30 min in 0.05-0.2 M NaOH for all the compounds with both the oxidants. The same twelve-electron stoichiometry per TSC was observed with dihalosulfonamides in partially aqueous medium (oxidant solutions in water-free acetic acid and reductant solutions in water) in 30 min with TSC and all its complexes. It was further noticed that the stoichiometric oxidations of the reductants take place within the specified time period with about 50% excess of the oxidants. If the percentage excess is low- ered the longer periods are required to achieve the stoichiometric oxidations. TSC in the metal complexes is oxidized faster than the TSC alone. So addition of the aqueous solution of a salt like ZnS04 to the reaction mixture was found to catalyze the oxidation of TSC alone.

RECOMMENDED PROCEDURES

(i) With monochlorosulfonamides (CAT and CAB). Adjust the pH of the reductant (TSC and its metal complexes) solution to any value between 3 and 5. Add aliquots of this solution (and 2 ml of 10% ZnS04 aqueous solution with TSC alone) to known excessive volumes (-50% excess) of 0.1 N oxidant (CAT or CAB) in iodine flasks and set aside the reaction mixtures for about 30 min with occasional shaking. Rinse down with about 20 ml of water, add 20 ml of 2 N HzS04 and 10 ml of 20% KI solution, and titrate the liberated iodine with 0.05 N sodium thiosulfate to a starch endpoint (V,,ml). Run blanks with the same volumes of the oxidant alone (CAT or CAB) (V,).

(ii) With monobromosulfonamides (BAT and BAB). Add aliquots of the reductant solution (and 2 ml of 10% ZnS04 aqueous solution with TSC alone) to known excessive volumes (-50% excess) of decinormal oxidant (BAT or BAB) in iodine flasks containing enough NaOH to maintain an overall concentration of 0.05-0.20 N alkali. Set the reaction mixtures


aside for about 30 min shaking occasionally. Complete the titration as under (i) adding sufficient amounts of acid solution (20 ml of 4 iV H$SOd).

(iii) With dihalosulfonamides (DCT, DBT, DCB, and DBB). Add aliquots of TX or its complex solution (and 2 ml of 10% ZnS04 solution with TX) to known volumes (-50% excess) of 0.1 N oxidant solution (DCT, DBT, DCB, or DBB) in iodine flasks maintaining an overall water content of about lo-20% and set aside the reaction mixtures for 30 min. Rinse down with about 50 ml of water, add 10 ml of 20% KI solution, and complete the titration as before.

The amount of TSC or its metal complex (X, kmol in the sample solution is given by

x = 103iv w2 - Vl)

E ’

where N is the normality of thiosulfate and E is the number of electrons changing per molecule of TSC; E = 12 with TSC alone and 24 with its complexes except PtL,(CN), PtLz(NCS)z, and PdLz(NCS)I, where E = 28, 40, and 40, respectively.

Although the Andrews type of direct titration of TSC and some of its complexes with some of the oxidants was found practicable in the presence of sodium acetate and KBr (and acetic acid in titrations with monochlorosulfonamides), the direct titrations are highly sensitive to the amounts of sodium acetate. So we did not pursue them further.

For determining reductants with iodamine-T and iodamine-B, the Pillai and Indrasenan method (28) was followed.

(iv) With monoiodosulfonamides (IAT and ZAB). Add measured volumes of reductant solution and 10 ml of 2 M potassium hydroxide solution to known excessive volumes (-50% excess) of 0.1 N IAT or IAB. Ther- mostat the reaction mixture with occasional shaking at 60°C for about 15 min. Then add 10 ml of 5 M hydrochloric acid and 10 ml of 20% potassium iodide solution and titrate the liberated iodine with 0.05 N thiosulfate using starch as the indicator near the endpoint (VI). Run blanks with the same volumes of the oxidant alone (IAT or IAB) (V,). Complete the calculation as before.

RESULTS AND DISCUSSION

The ligand TSC alone and in its metal complexes is oxidized with a twelve-electron change under present experimental conditions. It was noticed that the CN- and NCS- ions present in PtL2(CN)2, PtL,(NCS),, and PdLz(NCS)z are also oxidized by the oxidants (except IAT and IAB) under these conditions with a two- and eight-electron change per ion, respectively. With IAT and IAB, NCS ~ ion is oxidized with a six-electron


change while the cyanide is unaffected by these oxidants. These facts were taken into account while calculating the amount of the reductant present in a given sample solution.

Statistical evaluation of the results of the present analysis is shown in Tables 5-8. The maximum error encountered is about +0.7%.

Metal salts of monohaloamines (RNXM, where R = CsHsS02 or p- CH&H4S02; X = Cl, Br, or I; and M = Na or K) behave like electro- lytes (6) in aqueous solutions and dissociate as

RNXM = (RNX)- + M+

TABLE 5 STATISTICAL EVALUATION OF THE RESULTS OF THE DETERMINATIONS OF TSC AND ITS

METAL COMPLEXES BY p-TOLUENEHALOSULFONAMIDES

TSC (L)

or its

Amount

taken

Coefficient of variance” (%)

metal complex (wol) CAT DCT BAT

L 109.7 0.2 0.3 0.5

ZnL2S04 29.1 0.1 0.2 0.2

ZnL2C12 31.4 0.2 0.2 0.2

ZnL2WOd2 26.9 0.3 0.3 0.3

ZnL2(C104)2 22.4 0.4 0.4 0.5

CdL2S04 25.6 0.5 0.6 0.2 CdL2C12 27.4 0.4 0.3 0.3

&WA 22.0 0.5 0.6 0.4

NiL2S04 . 3H20 25.6 0.1 0.1 0.2

NiL2W03h 27.4 0.3 0.4 0.2

NiL2C12 32.1 0.2 0.1 0.5 Ni(L-H)? 41.8 0.4 0.5 0.3

PdL2C12 27.8 0.5 0.6 0.4 PdL2Br2 22.3 0.6 0.5 0.5

PdL212 18.4 0.6 0.5 0.6

PdL2(NCS)2 24.7 0.2 0.4 0.3 cis-PdL2(N03)2 24.2 0.3 0.5 0.3 rrans-PdLz(N03)2 24.2 0.3 0.5 0.4

Pd (L-H)2 34.9 0.4 0.4 0.5 cis-PtLQ 22.3 0.4 0.3 0.2

trans-PtLzCl* 22.3 0.5 0.4 0.3 PtL2Br2 18.6 0.6 0.6 0.3 PtL212 15.8 0.6 0.6 0.3

PtL,KN), 23.3 0.5 0.7 0.4 PtL2(NCS)2 20.3 0.4 0.5 0.3

PtLzWWz 19.9 0.5 0.7 0.3 Pt(L-H)* 26.6 0.4 0.2 0.2

DBT IAT

0.3 0.5

0.2 0.6

0.3 0.4

0.4 0.5

0.5 0.3

0.4 0.6

0.2 0.4

0.3 0.4

0.2 0.6

0.2 0.6

0.6 0.7

0.4 0.5

0.4 0.6 0.6 0.7

0.5 0.5 0.4 0.6

0.2 0.4

0.5 0.6 0.5 0.6

0.3 0.4 0.2 0.5

0.4 0.5

0.5 0.6

0.2 0.6

0.5 0.7

0.5 0.6

0.6 0.7

a Calculated for six trials.


TABLE 6

STATISTICAL EVALUATION OF THE RESULTS OF THE DETERMINATIONS OF TSC AND ITS

METAL COMPLEXES BY BENZENEHALOSULFONAM~DES

TSC (L) Amount or its taken

metal complex hmol) CAB

Coefficient of variance” (55)

DCB BAB DBB IAB

L 109.7 0.3 0.2 0.2 0.3 0.6

ZnLzS04 29.1 0.5 0.3 0.2 0.S 0.4

ZnL2C12 31.4 0.7 0.2 0.2 0.7 0.5

ZnL2WN2 26.9 0.5 0.2 0.2 0.5 0.3

ZnLz(ClO& 22.4 0.4 0.2 0.3 0.4 0.4

CdL2S04 25.6 0.5 0.2 0.3 0.5 0.S

CdLQ 27.4 0.3 0.2 0.2 0.3 0.6 HgL2Clz 22.0 0.7 0.2 0.3 0.7 0.7

NiL#04 . 3H20 25.6 0.4 0.4 0.2 0.4 0.4 NiLz(NO& 27.4 0.0 0.0 0.2 0.1 0.5

NiL2Cl2 32.1 0.6 0.6 0.2 0.6 0.6 Ni(L-H)z 41.8 0.3 0.3 0.1 0.3 0.7

PdLQ 27.8 0.4 0.3 0.2 0.4 0.7

PdLzBrz 22.3 0.4 0.3 0.2 0.4 0.7 PdL212 18.4 0.2 0.3 0.3 0.2 0.7

PdL2(NCS)2 24.7 0.5 0.2 0.2 0.5 0.6

cis-PdLz(NO& 24.2 0.6 0.2 0.2 0.6 0.6 tram-PdLz(NO& 24.2 0.6 0.2 0.2 0.6 0.6 Pd(L-H)2 34.9 0.2 0.2 0.2 0.2 0.7 cis-PtLzC& 22.3 0.4 0.0 0.2 0.4 0.6 frans-PtLzClz 22.3 0.4 0.0 0.2 0.3 0.6 PtL2Brz 18.6 0.4 0.3 0.3 0.2 0.7 PtLzIz 15.8 0.3 0.3 0.3 0.2 0.7

F’~Lz(CN)Z 23.3 0.2 0.2 0.2 0.2 0.7 PtL2(NC& 20.3 0.2 0.2 0.2 0.2 0.6

PUNO& 19.9 0.2 0.3 0.3 0.2 0.5 Pt(L-H)Z 26.6 0.3 0.2 0.2 0.3 0.6

a Calculated for six trials

The anions pick up protons in acid solutions to give the corresponding free acids, monohaloamine, RNHX (N-halobenzenesulfonamide or N- halo-p-toluenesulfonamide) (6, 16-18, 23).

(RNX)- + H+ = RNHX

Although the free acids have not been isolated there is experimental ev- idence for their formation in aqueous solutions (6, 16). They undergo disproportionation giving rise to benzenesulfonamide or p-toluenesulfonamide (RNHz) and dihaloamine-T (RNX2).

2 RNHX s RNHz + RNXz


TABLE 7 DETERMINATION OF TSC ANDITS METAL COMPLEXES BYE-TOLUENEHALOSLJLFONAMIDES

TSC (L) Range or its studieda

metal complex (wnol)

Maximum error in recovery (%)

CAT DCT BAT DBT IAT

L 21.94-548.6 0.5 0.5 0.6 0.6 0.6 ZnL2S04 5.82-145.5 0.1 0.2 0.5 0.5 0.5 ZnL& 6.28-157.0 0.3 0.4 0.5 0.5 0.6 ZnLdNOd2 5.38-134.5 0.5 0.5 0.5 0.5 0.6 ZnLK104)2 4.45-l 12.0 0.6 0.5 0.5 0.5 0.7 CdL2S04 5.12-128.0 0.4 0.5 0.4 0.4 0.6 CdL2Cl2 5.47-136.8 0.5 0.5 0.6 0.5 0.5 N&Clz 4.41-l 10.2 0.5 0.5 0.5 0.5 0.7 NiL2S04 . 3HzG 5.1 l-127.9 0.1 0.2 0.2 0.5 0.5 NiLWhh 5.48-137.0 0.3 0.5 0.6 0.4 0.6 NiL$& 6.41-160.3 0.5 0.4 0.5 0.5 0.5 Ni(L-H)z 8.37-209.2 0.6 0.6 0.6 0.6 0.7 PdL2C12 5.56-139.1 0.5 0.6 0.5 0.7 0.6 PdLzBr? 4.46-111.5 0.5 0.5 0.5 0.7 0.7 PdL& 3.69-92.2 0.5 0.6 0.5 0.5 0.7 PdL2(NCQ2 4.94-123.5 0.5 0.5 0.5 0.7 0.6 cis-PdLz(N03)z 4.85-121.2 0.5 0.4 0.5 0.6 0.7 rruns-PdL2(NO& 4.85-121.2 0.5 0.4 0.5 0.5 0.7 Pd(L-H)2 6.98-174.4 0.5 0.5 0.6 0.6 0.7 cis-PtLzCl2 4.46-111.5 0.5 0.5 0.6 0.6 0.6 truns-PtL$& 4.46-111.5 0.5 0.5 0.6 0.6 0.6 PtL2Brz 3.72-93.1 0.3 0.3 0.7 0.6 0.7 PtL212 3.17-79.2 0.5 0.4 0.7 0.6 0.7 PtLz(CNh 4.66-l 16.4 0.4 0.4 0.5 0.5 0.6 PtL2(NCS), 4.05-101.3 0.5 0.5 0.2 0.5 0.5 PUNOd2 3.99-99.7 0.5 0.6 0.6 0.6 0.6 Pt(L-H)2 5.33-133.2 0.5 0.6 0.5 0.6 0.7

n Each range covers the amounts present in 10 different aliquots of the compounds.

The dihaloamines and free acids hydrolyze to hypohalous acids (HOX) (16, 33).

RNX2 + HZ0 G= RNHX + HOX RNHX + HZ0 zs RNH2 + HOX

Finally, HOX ionizes as

HOX s H+ + OX-

The equilibrium constants for the above reactions are known only for chloramine-T (6, 23) and to some extent for bromamine-B (16).

Therefore the possible oxidizing species in acidified haloamine solu-


TABLE 8

DETERMINATION OF TSC ANDITS METALCOMPLEXES BY BENZENEHALOSULFONAMIDES

TSC (L) Range Maximum error in recovery (%)

or its studied” metal complex (bmol) CAB DCB BAB DBB

L 21.94-548.6 0.5 0.2

ZnL#.04 5.82-145.5 0.5 0.5 ZnLzClz 6.28-157.0 0.5 0.5

ZnL2WOd2 5.38-134.5 0.3 0.3

ZnL2(C104)2 4.45-l 12.0 0.6 0.6 CdLzS04 5.12-128.0 0.5 0.4

CdL2C12 5.47-136.8 0.5 0.5

W&h 4.41-l 10.2 0.6 0.5

NiL2SOd * 3HzO 5.1 I-127.9 0.6 0.6

NiMNO& 5.48-137.0 0.7 0.7 NiL2C12 6.41-160.3 0.4 0.5

Ni(L-H)2 8.37-209.2 0.5 0.5

PdLQ 5.56-139.1 0.7 0.6

PdLzBrz 4.46-111.5 0.5 0.3

PdL21z 3.69-92.2 0.7 0.5 PdLl(NCS)z 4.94-123.5 0.2 0.5

cis-PdL2(N03)2 4.85-121.2 0.5 0.5 truns-PdL2(N03)2 4.85-121.2 0.5 0.5

Pd(L-H)z 6.98-174.4 0.6 0.6 cis-PtLQ 4.46-111.5 0.5 0.5

frans-PtLzClz 4.46-111.5 0.5 0.5

PtLzBr2 3.72-93. I 0.5 0.7 PtL& 3.17-79.2 0.6 0.5

PtLACW 4.66-l 16.4 0.S 0.5

PtLI(NCS)? 4.05-101.3 0.4 0.2

PtMNOh 3.99-99.7 0.5 0.6 Pt(L-H)2 5.33-133.2 0.7 0.5

IAB

0.5 0.5 0.7 0.S 0.5 0.5 0.5 0.S 0.6

0.3 0.3 0.6 0.5 0.6 0.7

0.5 0.5 0.6 0.3 0.5 0.7

0.5 0.5 0.7

0.5 0.6 0.4 0.6 0.6 0.5

0,s 0.6 0.5

0.7 0.4 0.6 0.5 0.5 0.7

0.5 0.7 0.7

0.5 0.5 0.7 0.5 0.6 0.6 0.5 0.2 0.6 0.5 0.5 0.7

0.3 0.5 0.7 0.5 0.6 0.6

0.5 0.5 0.6

0.5 0.5 0.7 0.5 0.5 0.7

0.5 0.6 0.6

0.5 0.5 0.5

0.5 0.4 0.6

0.5 0.5 0.7

(1 Each range covers the amounts present in IO different aliquots of the compounds.

tions are RNHX, RNX?;, HOX, and possibly HzOX+ (and X2 in presence of X-). Bishop and Jennings (6) have calculated the order of the concentrations of the various species presented at different pH in a 0.05 A4 solutions of chloramine-T (Table 9). In the alkaline solutions the probable species are (RNX)- and OX-.

So the observed twelve-electron stoichiometry may be shown by

H2NNHCSNH2 + 6RNHX (or 3RNX2) + 6H20 + 6RNH2 (or 3RNH2) + SOj- + CO2 + N2 + NH$ + 6X- + 7H+ (1)

H2NNHCSNH2 + 6HOX + SOI- + CO2 + N3 + NHI; + 6X- + 7H+ (2)


TABLE 9 CONCENTRATIONS OF VARIOUS SPECIES PRESENT IN A 0.05 M CHLORAMINE-T SOLUTION

OVER A RANGE OF pH VALUES

PH RNCI - RNHCl RNClz = RNHz HOC1 0Cl-

0 9.60 x 1O-5 4.01 x 10-Z 9.90 x 10-X 3.95 x 10-7 1.30 x 10-14 1 9.60 x 1O-4 4.01 x 10-2 9.90 x 10-X 3.95 x 10-7 1.30 x 10-13 1.5 - 3.76 x 1O-2 - - - 2 7.80 x 10-j 3.24 x 1O-2 7.98 x 10-3 3.95 x 10-7 1.30 x 10-12 3 2.83 x 1O-2 1.18 x 1O-2 2.92 x 1O-3 3.95 x 10-7 1.30 x lo-” 4 3.84 x 10-2 1.60 x 10-j 3.95 x 10-d 3.95 x 10-7 1.30 x 10-10 5 4.00 x 10-2 1.67 x 1O-4 4.10 x 10-S 3.95 x 10-7 1.30 x 10-9 6 4.00 x 10-Z 1.67 x 1O-5 4.10 x 10-e 3.95 x 10-7 1.30 x 10-S 7 4.00 x 10-Z 1.67 x lO-6 4.10 x lo-’ 3.95 x 10-7 1.30 x 10-7 8 4.00 x 10-2 1.67 x lo-’ 4.10 x 10-8 3.95 x 10-7 1.30 x 10-6

H2NNHCSNH2 + 6H20X+ + SOi- + COz + N2 + NH1 + 13H+ + 6X- (3)

H2NNHCSNH2 + 6RNX- + 5H20 + OH- + 6RNH2 + SOi- + CO2 + N2 + NH2 + 6X- (4)

H2NNHCSNH2 + 60X- + 20H - + SOa- + COz + N2 + NHz,OH + 6X- + Hz0 (5)

Oxidation of CN- and NCS- ions present in the complexes may be rep- resented as

CN- + RNHX (or l/2 RNX2) + Hz0 + CNO- + RNH2 (or l/2 RNH2) + X- + Hf (6)

CN- + HOX+ CNO- + H+ + X- (7)

CN- + H20X++ CNO- + 2H+ + X- (8)

CN- + RNX- + H20--+ CNO- + RNH2 + X- (9)

CN- + OX-+ CNO- + X- (10)

NCS- + 4RNHX (or 2 RNX2) + 5H20 + SOj- + CNO- + 4RNH2 (or 2RNH2) + 4X- + 6Hf (11)

NCS- + 4HOX + H20+ SOa- + CNO- + 4X- + 6H+ (12)

NCS- + 4H2OX+ + H20+ SO]- + CNO- + 4X- + lOH+ (13)

NCS- + 4 RNX- + 3H20 + 20H- + Sot- + CNO- + 4RNH2 + 4X- (14)

NCS- + 40X- + 20H--+ SOi- + CNO- + 4X- + Hz0 (15)


Whenever six-electron change per NCS- ion was noticed the Eqs. (1 l)- (15) become:

NCS- -t 3RNHX (or 3/2 RNX2) + 4H20 -+ SOj- + CN- + 3RNHz (or 3/2 RNH2) + 3X- + .5H+ (16)

NC- + 3HOX + H20+ SOj- + CN- + 3X- + 5H+ (17)

NCS- + 3H2OX+ + H20+ So$- + CN- + 3X- + 8H+ (18)

NCS - + 3RNX- + 2Hz0 + 20H- -+ SOj- + CN- + 3RNH2 + 3X- (19)

NCS- + 30X- + 20H-+ SOi- + CN- + 3X- + Hz0 (20)

The presence of sulfate, CN-, and CNO- in the reaction products was detected by standard tests (II, 36, 37). Benzenesulfonamide formed in the reactions with benzene analogs was detected by TLC (34). A mixture of petroleum ether, chloroform, and n-butanol(2:2: 1 v/v) was the solvent, with iodine as the detection reagent (Rf = 0.88). p-Toluenesulfonamide, the reduced product of toluene analogs, was detected by paper chromatography with benzyl alcohol saturated with water as the soivent and 0.5% vanillin in 1% HCl in ethanol as the spray reagent (Rf = 0.91).

Common anions such as SOa-, PO]-, Cl04 , NO j, F- , Cl-, etc., do not interfere but CN-, hydrazine, urea, thiourea, etc., interfere in the estimation.

It can be concluded that the proposed analytical procedures are simple, rapid, and reproducible and are useful for determining thiosemicarbazide in solution and for computing the number of ligands present in the complexes.

SUMMARY

The behavior of 10 arylhalosulfonamides as oxidimetric analytical reagents toward thiosemicarbazide (TX) alone or in its metal complexes has been critically examined and general procedures for its estimation have been developed. The proposed analytical techniques are simple and reproducible. These procedures are also useful for computing the number of TSC ligands present in the complexes. The oxidation involves twelve-electron change per TSC molecule with all the oxidants. The complexes have been prepared and characterized by elemental analyses and IR spectra.

ACKNOWLEDGMENT

B.T.G. is grateful to the Government of India, New Delhi, for the award of a National Scholarship for Postdoctoral Research Abroad.

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determination of thiosemicarbazide alone and in its metal ... · microchemical journal 28,374-391...

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