f. Chem. SOC., Faraday Trans. I , 1982, 78, 3461-3466 Conductance and Viscosity Measurements of Te trabutylammonium Te t raphen ylboride in Non-aqueous Solvents at 25 OC BY DIP SINGH GILL,* MOHINDER SINGH CHAUHAN AND MADHU BALA SEKHRI Department of Chemistry, Himachal Pradesh University, Simla- 17 1005, India Received 8th December, 198 1 The equivalent conductance and viscosity of tetrdbutylammonium tetraphenylboride (Bu,NBPh,) have been measured in a large number of non-aqueous solvents at 25 O C and the data in all cases have been analysed by the Shedlovsky and Jones-Dole equations, respectively. The experimental A. value of Bu,NBPh, obtained from the conductance data in each solvent has been compared with the corresponding value obtained by adding together the ionic conductances of Bu,N+ and Ph,B-, which have been theoretically calculated using an equation proposed by Gill.The agreement between these two sets of A. values is good. The viscosity A coefficient of the Jones-Dole equation for Bu,NBPh, in each case is positive and is in good agreement with the limiting theoretical value calculated using the Falkenhagen-Vernon equation. The viscosity B coefficient is also positive and large in each case. The B+ and B- coefficients for Bu,N+ and Ph,B- have been calculated employing a method proposed in our previous paper and a justification based on conductance results has also been gwen for this method of separation. In one of our previous papers1-+ we reported the viscosities of some 1 : 1 electrolytes in NN-dimethylformamide + acetone mixtures3 The Jones-dole viscosity Bcoefficients for the electrolytes were split into the contributions due to individual ions using an assumption based on Bu,NBPh, as a reference salt.We found that such an assumption could be both simple and very useful in the evaluation of ionic B, and B- coefficients in pure and mixed non-aqueous solvent^.^ A detailed survey of the literature revealed that the viscosity of Bu,NBPh, has been measured in only a few non-aqueous solvent^.^ In order to emphasize the use of Bu,NBPh, as a reference salt for the evaluation. of ionic B, and B- coefficients from the B values of the electrolytes, we have measured the viscosity of this salt in acetonitrile (AN), acetone (Ac), ethyl methyl ketone (EMK), nitromethane (NM), nitrobenzene (NB), NN-dimethylformamide (DMF), NN-dimethylacetamide (DMA), dimethylsulphoxide (DMSO), propylene carbonate (PC), 1,1’,3,3’-tetramethylurea (TMU) and hexamethylphosphotriamide (HMPT).The equivalent conductance of Bu,NBPh, in most of these solvents has also not been available in the literature; we therefore measured the equivalent conductance of this salt, and the results are presented in this paper. EXPERIMENTAL All the solvents were purified by methods already reported.’. Tetrabutylammonium tetra- phenylboride (Bu,NBPh,) was prepared by the method of Accascina et af.8 Conductances were measured at 1000 Hz with a digital conductivity meter type NDC-732 supplied by Naina Electronics, Chandigarh. The details of the conductance cell and the experimental procedure for the conductance measurements have been reported earlier.2.4 , 346 13462 CONDUCTANCE A N D VISCOSITY MEASUREMENTS OF Bu,NBPh, An Ubbelohde suspended-level viscometer with flow time 756.4 s for water at 25 OC was used for the viscosity measurements. The method of calibration of the viscometer and the procedure for the viscosity measurements are given in ref. (3). The overall accuracy of the viscosity measurements was estimated as f 0.1 % and that of the conductance measurements as & 0.2%. RESULTS AND DISCUSSION CONDUCTANCE MEASUREMENTS The equivalent conductance of Bu,NBPh, has been measured in AN, Ac, DMF, DMA, DMSO, PC, TMU and methanol (MeOH) in the concentration range (1 - 80) x lo-, mol dm-3 at 25 OC. The equivalent conductance at infinite dilution (A,,) and the association constant KA in each solvent studied (reported in table 1) have been TABLE 1 .-EQUIVALENT CONDUCTANCE AT INFINITE DILUTION, A,(expt), THEORETICALLY CALCULATED EQUIVALENT CONDUCTANCE AT INFINITE DILUTION, A,(calc), THEIR PERCENTAGE DIFFERENCE AND THE ASSOCIATION CONSTANTS, KA, FOR Bu,NBPh, IN VARIOUS NON-AQUEOUS SOLVENTS AT 25 OC 120 (expt) KA A.(calc) Ao(expt) - Ao(calc) x 100 Ao(exPt) solvent /ap1 cm2 mol-l /mol dm-3 /a-l cm2 mol-1 AN Ac EMK NM NB DMF DMA DMSO PC TMU HMPT MeOH 120.0" 127.8" 102.8b 67.3c 22.3d 50.7" 45.3" 22.4" 1 7.6" 30.2" 12.2e 76.3" 11 15 - 17 30 - 121.8 131.4 105.2 68.2 22.5 52.4 45.4 23.1 18.1 30.8 12.6 75.4 - 1.5 - 1.9 - 2.4 - 1.4 -0.8 - 3.4 - 0.3 - 2.9 - 2.9 - 2.0 - 3.3 1.2 a Present work; R. M. Fuoss and E.Hirsch, J. Am. Chem. SOC., 1960, 82, 1013; S. R. C. Hughes and D. H. Price, J. Chem. SOC. A , 1967,1093; ref. (1 5). C. Atlani, J-C. Justice, M. Quintin and J. E . Dubois, J . Chim. Phys., 1969, 66, 180. calculated iteratively by a least-squares treatment with an IBM- 1620 computer using Shedlovsky's method,l09 l1 as discussed in detail in our previous papem27 The viscosity (q) and the dielectric constant ( E ) for the analysis of conductance data were taken from our previous papers.l* The mean ion activity coefficients for that purpose were calculated using the equation suggested by Justice.12 Activity-coefficient measurements by Gill and Malhotra13 in DMF show that such an equation for the evaluation of mean ion activity coefficients of electrolytes is justifiable.The standard deviations in A, and KA values given in table 1 obtained by applying standard statistical equations14 were found to be always less than +0.2% and The root-mean-square deviations oA calculated from the standard deviations of the individual points in no case exceeded the experimental uncertainty of the present conductance measurements, i.e. + 0.2%. This shows the good applicability of the Shedlovsky equation to our conductance data. As the precision of our conductance lo%, respectively.D . S. GILL, M. S. CHAUHAN A N D M. B. SEKHRI 3463 data is ca. +0.2%, the use of a conductance equation which demands a precision in the conductance data much better than +0.1% was not thought appropriate to analyse the present conductance data. To indicate the precision of the present conductance data, our A, values from table 1 are compared with values already available in the literature.Our A, values for Bu,NBPh, of 120.0 in AN, 76.3 in MeOH and 22.4 in DMSO are in good agreement with the A. values 119.7, 76.0 and 22.2 S2-l cm2 mol-l reported by Coetzee and Cunningham,15 Coplan and FUOSS~~ and calculated from the A: values of Arrington and Griswold17 in AN, MeOH and DMSO, respectively. PREDICTION OF A. VALUES FOR Bu,NBPh, I N NON-AQUEOUS SOLVENTS In our previous papers2? we proposed an equation which theoretically predicts limiting ion conductances of Bu,N+ and Ph,B- in pure and mixed non-aqueous solvents with an average uncertainty of _+ 2% in comparison with the values obtained from direct transport numbers when ri values for Bu,N+ and Ph,B- are taken in this equation to be 5.00 and 5.35 A, respectively.This equation can be written as A: = 121 F2/6nr N [ri-(O.O103~+r,)] (1) where all the symbols have their usual significance2. 6. Using ri equal to 5.00 and 5.35 A for Bu,N+ and Ph,B-, respectively, and rY equal to 0.85 A for all the solvents reported in table 1 , A: values for these two ions have been theoretically calculated from eqn (1). The q and E values for various solvents were taken from our previous papers.lV By adding these A: values for Bu,N+ and Ph,B-, A, values for Bu,NBPh, in various solvents have been calculated and are reported as A,(calc) values in table 1 . A comparison between the theoretically calculated A,(calc) values and the experimentally measured Ao(expt) values shows fairly good agreement (see the percentage difference between these two sets of values reported in the last column of table 1).VISCOSITY MEASUREMENTS The viscosity of Bu,NBPh, has been measured in AN, Ac, EMK, NM, NB, DMF, DMA, DMSO, PC, TMU and HMPT in the concentration range (30-250) x lo-, mol dm-3 at 25 OC. Plots of the Jones-Dole equation18 qr = l + A Cg+B C (2) in the form (qr - 1)/Ci against Cg were linear in all cases over the whole concentration range studied and the A coefficients for Bu,NBPh, in all the solvents, obtained from the intercept of these plots, were positive (table 2) and in good agreement with the corresponding A , coefficients calculated from the Falkenhagen-Vernon equationlg where A, = A: + A;, A: and At are the limiting ion conductances for Bu,N+ and Ph,B-, q and E are the solvent viscosity and the dielectric constant of the solvent, respectively, and Tis the absolute temperature.For the calculation of A , from eqn (3), A, values for Bu,NBPh, were taken from table 1 and the A; values for Ph,B- were calculated using A: values for Bu,N+ reported in our previous paper.6 For the solvents in which Bu,NBPh, was unassociated (table 1) the B coefficients (reported in table 2) were obtained from the average value of the (practically constant) apparent B coefficients calculated at each concentration obtained using the3464 CONDUCTANCE AND VISCOSITY MEASUREMENTS OF Bu,NBPh, THE FALKENHAGEN-VERNON EQUATION FOR Bu,NBPh, IN NON-AQUEOUS SOLVENTS AT 25 O C TABLE 2.-A AND B COEFFICIENTSa OF THE JONES-DOLE EQUATION AND A,, COEFFICIENT OF solvent lo2 A,/(dm3 mo1-l): A / (dm3 mo1-l); AN Ac EMK NM NB DMF DMA DMSO PC TMU HMPT 2.43 3.39 3.63 2.40 2.52 2.40 2.33 1.96 1.70 2.97 2.77 2.30 3.20 3.70 2.00 2.40 2.80 2.40 1.80 1.60 3.00 3.20 B/dm3 mol-l 1.32 f 0.02 1.54 f 0.02 2.02 f 0.03 1.29 50.06 1.40 f 0.02 1.96 _t 0.03 1.93 & 0.02 1.45 f 0.04 1.46 f 0.02 2.01 f 0.04 2.99 & 0.06 - a The A coefficients in this table have a maximum uncertainty of f 10%.Falkenhagen-Vernon A, coefficient from table 2 and the equation r,-l-A,Ct c * B = (4) However, for the solvents in which Bu,NBPh, showed ion association, the B coefficients (reported in table 2) were obtained using the following equation3 vr - 1 - A , (Ca)e Ca = B + B KA Ca fg and a graphical method whose details are discussed in our previous paper.3 The viscosity B coefficient for Bu,NBPh, in all the solvents is large and positive.This is a common feature of most non-aqueous solvents. In non-aqueous solvents, the structure-breaking contribution is negligible, with the result that the B coefficient is always positive and large. Our B coefficients for Bu,NBPh, in AN (1.32+0.02), in Ac (1.54+0.02) and in DMF (1.96k0.03) dm3 mol-l from table 2 are in good agreement with the values 1.35, 1.56 and 1.86 reported by Tuan and FUOSS' in AN and by Gill and Sharma3 in Ac and DMF, respectively. Our Bcoefficient for Bu,NBPh, in HMPT 2.99 0.06 is, however, higher than the value of 2.58 dm3 mol-l reported by Sacco et a/.20 in this solvent. B+ AND B- COEFFICIENTS FOR BU,N+ AND Ph,B- I N VARIOUS NON-AQUEOUS SOLVENTS The splitting of the B coefficient of electrolytes into the contributions due to individual ions cannot be made in the same way as the division of limiting equivalent conductances, since there is no quantity corresponding to the transfer numbers.Accordingly, the separation of the observed B coefficients has been an arbitrary p r o c e ~ s . ~ ~ - ~ ~ In a previous paper3 we proposed a method for splitting the B coefficient of electrolytes into the contribution due to individual ions on the basis of the following equations : and (7)D. S. GILL, M. S. CHAUHAN AND M. B. SEKHRI 3465 The present conductance measurements in various solvents have also confirmed that the experimental A, values for Bu,NBPh, are in good agreement with the theoretically calculated A, values when the ri values for Bu,N+ and Ph,B- in eqn (1) are taken to be 5.00 and 5.35 A, respectively, in all the solvents. This justifies our approach to the evaluation of the ionic B, and B- coefficients from eqn (6) and (7) using Bu,NBPh, as a reference salt.Using eqn (6) and (7), the B coefficients of Bu,NBPh, in various solvents given in table 2 have been resolved into the contributions from Bu,N+ and Ph,B-, and the values thus obtained are reported in table 3. The maximum uncertainty in the B, and B- values of table 3 is k0.06 dm3 mol-l. TABLE 3.-lONIC B, AND B- COEFFICIENTS' FOR BU,N+ AND Ph,B- IN NON-AQUEOUS SOLVENTS AT 25 "C EVALUATED FROM EQN (6) AND (7) solvent B+/dm3 mol-l B-/dm3 mol-l AN Ac EMK NM NB DMF DMA DMSO PC TMU HMPT 0.59 0.69 0.91 0.58 0.63 0.88 0.87 0.65 0.66 0.90 1.34 0.73 0.85 1 .1 1 0.71 0.77 1.08 1.06 0.80 0.80 1 . 1 1 1.65 The B,. and B- coefficients in this table have a maximum uncertainty of & 0.06 dm3 mo1-l. There are practically no viscosity data available in the literature for electrolytes in all these non-aqueous solvents. Therefore, a comparison of our B, and B- values from table 3 cannot be made. Some precise viscosity measurements of electrolytes have been recently reported by Bicknell et a1.26 in DMSO. Our B- value for Ph,B- [equal to 0.80_+0.06 in DMSO from the present method of separation (table 3)] is in good agreement with the value of 0.72 dm3 mol-l reported by Bicknell et al.26 using an independent approach to the separation.M.S.C. and M.B.S. are grateful to the C.S.I.R., New Delhi, for the award of a Research Fellowship. The authors thank Mr Amar Nath Sharma for the computer analysis of the conductance data. A research grant from the U.G.C., New Delhi, is gratefully acknowledged. ' D. S. Gill, J . Solution Chem., 1979, 8, 691. D. S. Gill and M. B. Sekhri, J . Chem. SOC., Faraday Trans. 1, 1982, 78, 119. D. S. Gill and A. N. Sharma, J. Chem. Soc., Faraday Trans. I , 1982, 78, 475. D. S. Gill and J. S. Cheema, Electrochim. Acta, in press. D. S. Gill, A. N. Sharma and H. Schneider, J . Chem. SOC., Faraday Trans. I , 1982, 78, 465. D. S. Gill, J . Chem. SOC., Faraday Trans. I , 1981, 77, 751. ' D. F-T. Tuan and R. M. Fuoss, J. Phys. Chem., 1963, 67, 1343. F. Accascina, S. Petrucci and R.M. Fuoss, J . Am. Chem. SOC., 1959, 81, 1301. D. S. Gill and J. S. Cheema, Electrochim. Acta, 1982, 27, 755. lo R. M. Fuoss and T. Shedlovsky, J . Am. Chem. SOC., 1949, 71, 1496.3466 CONDUCTANCE AND VISCOSITY MEASUREMENTS OF Bu,NBPh, l 1 R. M. Fuoss and F. Accascina, Electrolytic Conductance (Interscience, New York, 1959). l3 D. S. Gill and K. Malhotra, Indian J. Chem., 1980, 19A, 65. l4 W. J. Youden, Statistical Methods for Chemists (John Wiley, New York, 1951), p. 42. l5 J. F. Coetzee and G. P. Cunningham, J . Am. Chem. Soc., 1965, 87, 2529. J-C. Justice, Electrochim. Acta, 197 1, 16, 701. M. A. Coplan and R. M. FUOSS, J. Phys. Chem., 1964,68, 1 177. D. E. Arrington and E. Griswold, J. Phys. Chem., 1970, 74, 123. G. Jones and M. Dole, J . Am. Chem. SOC., 1929, 51, 2950. J. 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