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Chlorosulphuric Acid As Anon-Aqueous Solvent

Chlorosulphuric Acid As Anon-Aqueous Solvent

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2. PAUUK, F., PAUUK, J. & ERDY, L., Talanta, 13 (1966), from high purity selenium and tellurium metalsc• 1405; Analytica chem. Acta, 34 (1966), 419. Selenium mono chloride was prepared and purified 3. FLANIGEN, E. M., KHATAMI, H. & SZYMANSKI, H. A., Molecular sieve zeolites, Advan. Chern. Ser. 101 by the reported method6• tribromide (American Chemical Society, Washington), 1971, 201. and pentabromide were prepared as reporteds. Phos• 4. CLARK, R. J. H. & WILLIAMS, C. S.,lnorg. Chem.,4 phorus pentachloride was sublimed in pure chlorine (1965), 350. gas and kept in vacuo over P206• Phosphorus tri• 5. KHAmY, E. M., MAHGOUB, A. E. & KENAWI, I. M., Egypt J. Chem., 17 (1976), 811. chloride was distilled on a water-bath and the fraction 6. KANIPPAYOOR, RAVEENDRAN, K. & BANERJEE, SATI ofb.p. 75-76°, was used. Arsenic trichloride was PRAsAD, Cent. Glass ceram. Res. lnst. Bull., (in press). distilled under dry nitrogen atmosphere and the 7. BANERJEE, SATI PRAsAD, J. Indian chem. Soc., 55 (1978), 99. fraction b.p. 223-224° 740 mm was used. Antimony 8. SRIVASTAVA, MALTI & BANERJEE, SATI PRAsAD, J. Inst. trichloride was purified by fractional distillation Chemists (India), 50 (1978), 264. and the fraction of b.p. 223° was used. 9. AsrAKHov, V. A., MEERSON, L. A. & KLYUSHKOVA, The method of conductance measurements and Vestsi Akad. Nauk BSSR, Ser. Khim, 3 (1978), 118; Chem. Abstr., 89 (1978), 65907. the determination of y, the number of SOaO- produced per mole of the solute have been described earlier7• UV and visible spectra of the solutions were recorded on a Beckman spectrophotometer using quartz cells. Chlorosulphuric Acid as ANon-aqueous Solvent : Interpolated values of the specific conductivity of Part XII-Behaviour of Some Inorganic Halides in various solutes in chlorosulphuric acid have been Chlorosulphuric Acid presented in Table I. Unlike the solution of selenium tetrachloride in R. C. PAUL, D. S. DHILLON, D. KONWER & J. K. PuRl· chlorosulphuric acid2, the solution of selenium Department of Chemistry, Panjab University, tetrabromide in this acid is always accompanied Chandigarh 160 014 with the evolution of S02 gas. The solution is highly conducting and unstable. The colour of the Received22 June 1978; revised 26 December 1978; rerevised and solution is reddish-brown similar to that of accepted 22 September 1979 in chlorosulphuric acid. It may be assumed that Tetrabromides of selenium of tellurium form SeBrt and probably , produced during the TeBrt ions, when dissolved in chlorosulphuric acid. Solution reaction, is further oxidised by free sulphur trioxide of selenium monochloride in chlorosulphuric acid contains both (obtained from the self-dissociation of the solvent) to liberate free bromine. However, the conductance Seat and Se:+ ions. forms PClt ions in chlorosulphuric acid while behaves data, when extrapolated to zero time and compared as a very weak base. and pentabromide with that of potassium chlorosulphate in chloro• are oxidized in chlorosulphuric acid to from phosphoryl sulphuric acid, suggest the following mode of re• which is further protonated by the acid. Trichlorides of arsenic action of SeBr4' and antimonysolvolyse when dissolved in chlorosulphuric acid. 2SeBr4 + 4HSOsCI ~ 2SeBrt + 2S0sCI- + Br2 + H2S04 + 2HCI + S02 pAUL and coworkers1 have studied the behaviour y == I .. (1) of various inorganic halides in disulphuric acid. Robinson and Ciruna2 have shown the formation The above reaction is further supported by UV of SeClt and TeCI+a ions by dissolving SeCl4 and spectrum of the solution which shows the absorp• TeCl4 in chlorosulphuric acid. In the present note, tion band at 280 nm (EM == 1050) which is attri• we report the behaviour of some more inorganic buted to the presence of sulphur dioxide in. the halides in chlorosulphuric acid which may be helpful above reaction. Sulphur dioxide and bromine, pro• in understanding the true nature of these halides. duced in the above reaction, behave as non-electro• Chlorosulphuric acid (BDH, reagent grade) was lytes in chlorosulphuric acid whereas H2S04 and used directly as suggested by Robinson and Cirunaa. HCI are veIY weak basesa of the system. TeBr. Selenium and tellurium tetrabromides were prepared shows a similar behaviour in chlorosulphuric acid.

TABLE 1 -' 1.9051.4150.1050.1150.7852.1850.0950.7050.120.7250.8850.1350.3850.5851.5050.0850.1250.6000.8250.9251.3201.6150.040.081.6251.4050.060.101.7150.0900.0800.181.3151.5751.6050.8051.1051.1251.3050.7151.5100.8101.2150.4052.3051.7551.6650.6250.4250.141.4251.815Q.4151.8250.4001.2101.1151.0501.2051.8051.4150.16INTERPOLATED0.905 VALUES0.0600.1950.3150.0550.0500.2250.2150.200 OFSp.SPECIFICcondo atCoNDUCfANCESthe concentrationOF VARIOUS(equivalents/kgINORGANICoflIALIoESthe solution)IN CHLOROSULPHURIC ACID AT 25° PBrsPBr.pasTeBr.PClsAsClsSbCl.SeBr. Compounds SesCI. 0.02 473 INDIAN J. CHEM., VOL. 19A, MAY 1980

The ormation of SeBrt and TeBrt ions in chlo• these frequencies for P-CI are slightly lower than rosulp uric acid is quite possible, since these ions those reported for Si-Cl in isoelectronic SiCl4 have a ready been established to exist by Paul and due to the formal charge on PClt. These obser• cowor ersi in disulphuric acid. vations agree with the reported vibrations of this Sele ium mono chloride when dissolved in chloro• in the solid state and support the mode of sulphu ic acid, forms green solution which slowly ionization of these solutes as suggested earlier. change to yellow. It has already been reported Phosphorus trichloride dissolves in HSOaCI to that s lenium monochloride disproportionates in give solution with very little change in conductance, certain highly acidic solvent as : which indicates that it behaves as a very weak electro• lyte in this solvent systems. But the solution of 2 e2Cl2 ------+ SeCl4 + 3Se phosphorus tribromide in chIorosulphuric acid gives In chI rosulphuric acid solvent also probably smell of S02 indicating that some oxidation reaction seleni mono chloride disproportionates to give takes place. It may be assumed that phosphoryl eleme al selenium and selenium tetrachloride. bromide is formed which is further protonated in Eleme tal selenium, thus formed, reacts further with the solvent. The solution has a quite good conduc• the so vent to form green solution (due to Se2jj tance. From the conductance data the possible cation which slowly changes to yellow in colour mode of reaction may be suggested as (Eq. 3), due t the formation of cation)D. UV and Se2! PBra + 2HSOaCI---+ P(OH)+ Bra + SOaCI- visible spectra of the yellow solution show the pre• sence f Se:+ cation in solution. Selenium tetra• + HCI + S02 .. (3) chlori , so produced is further ionized in chloro• (y < 1) sulphu ic acid to form SeCI! ion. IR spectrum of the ab ve solution shows bands at 370, 340, 260, From the y value obtained, it has been 'concluded 560, 5 0, 780, 1070, 1240 and 1340 cm-I. The bands that POBra, formed in the reaction, undergoes at 370,340 and 260 cm-I are due to the cation SeClt . incomplete proton ation in chlorosulphuric acid, The b nding mode (V2)which is usually found in while in disuiphurici acid, it behaves as a fully the so id state at 385 cm-I is shifted to 370 cm-I, protonated base. sugges ing a slight solvation of the cations by the Unlike phosphorus pentachloride, phosphorus solven molecule. The bands at 560, 580, 1070, pentabromide dissolve in HSOaCI accompanied with 1240 d 1340 cm-I are due to chlorosulphate ion the evolution of S02 gas to form a reddish-brown and c nform to the mode of the ionization as solution which is stable and has a quite good con• report d earlier. UV spectrum of the solution of ductance. The colour of the solution is similar to seleniu monochIoride in chIorosulphuric acid that of bromine solution in HSOaCl. It has already shows bands characteristic of Se:+ and sulphur been reported that dis• dioxid 9. However, from the above spectral studies sociates to phosphorus tribromide and free bromine and t conductance data the overall reaction may in certain highly acidic solvents. Phosphorus tri• be rep sented by Eq. 2, bromide thus formed is oxidized by the solvent to which is further protonated in 8Se2 12+ 16HSOaCI---* 3Se:++ 4SeCIt + it. The possible mode of reaction of phosohorus pentabromide in HSOaCI may be suggested as shown IOS0aCl- + 3H2S04 + IOHCI + 3S02 in Eq. 4. (y=1.25) .. (2) PBr5 + 2HSOaCl--+ P(OH+)Bra + SOaCl• Pho phorus pentachIoride readily dissolves in + Br2 + HCI + S02 chIoro ulphuric acid to form highly conducting (y < 1) .. (4) soluti n which is quite stable. From the conduc• tance atarit has been suggested that probably phos• However from the y value obtained, it has been phoru pentachloride first reacts with the free sulphur observed that phosphorus pentabromide also behaves trioxi (obtained from the self-dissociation of the as a weak electrolyte in chIorosulphuric acid. The solven) to form the compound PClt SOaCl- which presence of sulphur dioxide in the above reaction is is furt er ionized in chlorosulphuric acid to give further confirmed from the UV spectrum of the PClt ion, solution as discussed earlier .. Arsenic trichloride has been known to form ionic PCl + HSOaCI -+ PClt SOaCl- + HCl --+ complexes with stronger lewis acids such as SbCI~3 PClt + SOaCr- + HCI and BCI~4 and the ions have been formulated as y < 1 AsClt .BCI4 and AsCI! SbCI-; respectively. Con• ductometric titrations between acidsI5 and basesl'• The above reaction is further supported by the IR have shown the occurrence of autoionization as : spectr m of the solution [bands at 1160, 1030, 840,

750, 6 0, 570, 485 cm-I in comparison to IR bands 2AsCla ;=:!: AsClt + AsCI~ of PC t reported at 640, 570, and 485 cm-I by Beatti et al.IO]. The IR bands at 640, 570, 485 But unlike other ionic compounds, there is no appre• cm-I n PClt are due to P-Cl asymmetric com• ciable change in the conductance of the solution binati n band (~I + V4)and asymmetric stretching when arsenic trichloride is dissolved in chlorosul• vibrat ons for the cation PClt . As suggested earlier phuric acid. Since there is evolution of HCI during

474 NOTES the reaction, the following two mode of solvolytic Kinetics & Mechanism of Oxidation of Proline by reaction are possible, Chloramine- T + AsCla + HSOaCI---+ HAsCla + SOaCI- .. (5) JANARDHANSHARMA, LALH PANDEY & S. P. MUSHRAN* AsCla + 3HSOaCI---+ As(SOaClh + 3HCI .. (6) Department of Chemistry, University of Allahabad, Allahabad 211 002 The reaction (5) is ruled out as the solutions are non-conducting. Moreover when potassium chioro• Received 16 Ju/y 1979; revised and accepted 6 September 1979 sulphate is added, there is a slight increase in the conductance of the solution, but the slope of the conductance-composition curve is less than that in The title reaction has been suggested to proceed through two the case of pure potassium chlorosulphate suggesting pathways. (i) Interaction of N-chloro-p-toluene-sulphonamide that arsenic trichloride when solvolysed in HSOaCI molecule, produced in a fast step from CAT, with proline in a behaves as an acid and reaction (6) is more probable. slow step resulting in the formation of an ~termediate, N-chloro• However, in the case of arsenic tricWoride, the solu• proline which in a subsequent fast step interacts with another tions have been shown to behave as an acid when molecule of N-chloro-p-toluenesulphonamide yielding the products potassium chlorosulphate is added, (allyl cyanide, HCI and carbon dioxide). (ii) In this pathway hypo• chlorite ion replaces N-chloro-p-toluenesulphonamide in the above As(SOaCl)a + SOaCI ---+ As(SOaCI)~ steps. Both the mechanisms satisfy the observed stoicbiometo>, From the conductance data alone, it is very difficult negligible influence of ionic strength and a positive dielectric eft'ect. to determine the extent of the solvolysis of AsCla. Various possible ions present in the solutions may be THE kinetics of oxidation of «-amino acids explained on the basis of Eqs 7-9. using a variety of oxidants have been studied AsCla + HSOaCI -~ AsCI2(SOaCI)+ HCI by several workers1-a. In continuation of our investi• .. (7) gations on the oxidations of organic compounds~7 AsCla + 2HSOaCI---+ AsCI(SOaCI)2+ HCI .. (8) by chloramine-T (CAT), the present paper deals with the kinetics and mechanism of oxidation of proline AsCla + 3HSOaCI------+ As(SOaClh + 3HCI .. (9) by CAT in alkaline medium. All the·reagents used, were of highest purity avail• Antimony trichloride behaves in a similar manner able. Aqueous solution of CAT (E. Merck) was to that of AsCla in chlorosulphuric acid. These solid prepared and stored in dark-coloured bottle. Aqueous solvates, which separated out after solvolysis, were solution of proline [Pro] was prepared using AR further washed with anhydrous methylene chloride (BDH) sample. Triply distilled water was used for and dried in vacuo and finally analysed. They corres• the preparation of all solutions. All other reagents pond to the composition, M(SOaClh where M = used were of AR grade. The method for kinetic As, Sb. Their IR spectra show the presence of measurements has been described in our previous SOaCI- group. paper4. The experiments conducted to establish the stoi• References chiometry revealed that two mol of CAT consumed 1. PAUL, R. C., KAPILA, V. P., PUIu, J. K. & MALHOTRA one mol of [Pro] to give allyl cyanide, detected by K. C., J. chem. Soc. (A) (1971), 2132. conventional analytical methodS. 2. ROBINSON, E. A. & CmUNA, J. A., Can. J. Chem., 46 (1968),3197. The oxidation of [Pro] by CAT was studied over a wide range of concentrations of the reactants. Owing 3. ROBINSON, E. A. & CmUNA, J. A., Can. i. Chem., 46 (1968), 1719. to high concentration of alkali, no buffer could be 4. BRAUER,G., Handbook of preparative , employed. The first order dependence of reaction Vol. 1 (Academic Press, New York), 1963, 422. rate on CAT was established by the co~tant values 5. BRAUER,G. Handbook of preparative inorganic chemistry, of first order rate constant (kl') in CAT (Table 1) at Vol. 1 (Academic Preas, New York), 1963,422. all initial concentrations of the oxidant. 6. FERNELlUS,W. C., Inorganic syntheses, Vol. 2 (McGraw• Hill Book Company, New York), (1946), 147, 151. 7. PAUL, R. C., DHILLON,D. S., KONWER,D. & PUIu, J. K., TABLE1- EFFECf OF VARYINGREACfANTCoNCENTRATIONON J. Inorg. Nuc/., Chem.39 (1977), 1011. REACTIONRATE 8. KONWER, D., Solution chemistry in ch/orosu/phuric acid, [NaOH] = 15.8 x 10-1 M . Ph. D. Thesis, Panjab University, Chandigarh, 1977. 9. PAUL, R. C., KONWER,D., DHILWN, D. S. & PUIu, J. K., 100[CAT] IOI[Pro] k1' x lO' (sec--1) at Inorg. Nuc/. Chem. Letters, 13 (1977), 389. M 2.00.60.8Lo1.4M1.013.813.113.025.613.612.818.635°10.820.021.321.020.840°42.330.219.88.217.2 10. BEATTIE,I. 0.81.02.0R.,1.4 LIVINGSTONE,K. & WEBSTER,M., J. chem. Soc., (1965),0.6 7421. 11. CORDES,A. W. & HUGHES,T. V., Inorg. Chem., 3 (1964), 1~ .. 475 12. GEORGE, J. W., KATSAROS,NAND WYNNE, K. J., Inorg. Chem., 6 (1967), 904. 13. GUTMANN,V., Monatsch. 83 (1952) 159. 14. LINDQUIST, I., Acta Chem. Scand., 9 (1955), 73. 15. GUTMANN,V., Z, anorg. Chem., 266 (1951), 331. 16. GUTMANN,V., Monatsch, 82 (1950), 473.

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