271
DIPOLE MOMENT on CERTAIK SULFONAMIDES
Feb.. 1963
DIPOLE MOMENT OF CERTAIN SULFONAMIDES' BY W. K. PLUCKNETT AND H. P. WOODS Department of Chemistrg, University of Kentucky, Lexington, Kentucky Received July 6, 1962 Dielectric constants and densities of dilute solutions of N-methylmethanesulfonamide, N,N-dimethylmethanesulfonamide, S-methylbenzenesulfonamide, and N ,N-dimethylbenzenesulfonamide in benzene have been determined a t 25, 35, 45, and 55". Dipole moments by both the Debye temperature-dependence and refraction methods have been calculated. Both methods agrlee for the disubstituted sulfonamides. However, poor agreement is found for the monosubstituted compounds. This is attributed to dimer formation by means of hydrogen bonds. Since the monomer-dimer equilibrium constant for N-methylmethanesulfonamide in CCl4 at 25' is available, the data are analyzed to calculate approximate dipole moments for the monomer and dimer of this compound. The cis configuration of the dimer appears to be consistent with the data.
Introduction Vaughn and Sears2have reported dielectric constants for K-methylmethanesulf onamide (NMMSA), N ,N-dimethylmethanesulfonamide (DMMSA), K-methylbenzenesulfonamide (NMBSA), and N,N-dimethylbenzenesulfonamide (DRIBSA) of 90.0, 80.4, 60.1, and 48.6, respectively, a t 50' and 1 Mc. The small difference between the dielectric constants of the N-methylsulfonamides and the K,N-dimethylsulfonamides, together with a much smaller temperature coefficient of dielectric constant than the analogous carboxylic amides, led these investigators to conclude that the molecular properties causing high dielectric constants in the sulfonamides differ from those of the carboxylic amides. The purpose of this investigation was to provide additional information which might be used in the study of the relationship between dipole moment and the dielectric constant for highly polar liquids, such as the substituted sulfonamides. The dipole moment of benzenesulfonamide has been reported as 4.75 D.3and 4.73 D.* in benzene and 5.09 D.4-6 in dioxane. More recently Estok and Sood7 obtained moments of 4.84 and 5.12 D. in benzene and dioxane, respectively, from extrapolated mixed solvent data. These values indicate an abnormal solvent effect, or interaction between solute and solvent, for benzenesulfonamide. Estok and Sood concluded from their work that benzenesulfonamide is not appreciably associated. Ethanesulfonamide with a dipole moment4of 4.03 D. in benzene and 4.62 D. in dioxane has a solvent effect approximately twice that of benzenesulfonamide in the same solvents. Dipole moments in dioxane of 5.07 and 4.96 D. for Nphenylbenzenesulfonamide and N-acetylbenzenesulfonamide, respectively, have been reported by Pushkareva and Kokoshko.6
The DMMSA was prepared according to the proceduro of Vaughn and Sears.2 It had the following properties: m.p., 48.0-48.5'; n56~ 1.4339; d6541.1582. Samples of NMMSA, NMBSA, and DMBSA were supplied in the purified form by these same investigators. Their physical properties have been p~blished.2 Dielectric constants and densities of dilute solutions of the sulfonamides in benzene were determined at four or five concentrations and a t 25,35,45, and 55". Apparatus and Procedures.-The dielectric constants were determined with a heterodyne-beat apparatus similar in deriign t o that described by Chien.8 The fixed-frequency oscillator was controlled by a 1-Mc. crystal. A General Radio Precision condenser, Type 722-D, with a range of 25 to 100 absolute ,upf, was used as a standard condenser. In order to eliminate the uncertainty associated with null-point detection, a 1000-c. Central Scientific Co. audio frequency oscillator (Model 70029) and a Waterman Pocketscope (Model S-104) oscilloscope were used for beat indication. The physical connections and theoretical considerations pertinent to this method of beat detection are clearly given by Daniels.9 The dielectric cell used has been described in detail by Leader.10 Temperature was controlledwith a precision of f:0.05' a t 25 and 35' and dz0.1" a t 45 and 55" by rapidly circulating water from a constant-temperature bath through the jacket of the dielectric cell. Air and benzene with dielectric constants of unity and 22.74,11respectively, a t 26' were used as standard media. As a check on the calibration the dielectric constants of m- and p-xylene were found t o be 2.364 and 2.261, respectively, a t 25' compared to literature" values of 2.364 and 2.262, respertively. Densities were determined in the convenBiona1 manner wing 25-ml. Reischouer specific gravity bottles. Values were precise t o 10.0001 g./ml. at all temperatures.
Results and Discussion Dipole moments were calculated by two methods, the Debye temperature-dependence method and the refraction method. For both methods the data were treated in the manner of Hedestrandia to obtain the limiting value of the solute polarization a t infinite dilution, Pzm. This is given by eq. 1, where D , d , and
Experimental Materials.-Thiophene-free benzene was refluxed for 12 hr. M represent dieIectric constant, density, and molecular over roarited calcium oxide prior to distillation through a 4-ft. weight, respectively, with subscripts 1 and 2 representvacuum-jacketed column packed with glass helices. The coning solvent (benzene) and soIute, respectively, and a stant .boiling middle fraction which was used in the preparation of all solutions had the following properties: f.p. 5.45'; V L : ~ ~ D and b represent the slopes of the plots of Dlb ahd dlz 1.4979; P 4 0.8730. 218. A i s , respectively, where the subscript 12 represents (1) Taken in part from a thesis submitted by H. P. WoodB in partiaI fulfillment of the requirements for the degree of Master of Science, (2) J. W. Vaughn and P. G. Sears, J. Phga. Chem., 62, 183 (1858). (a) E.N. Gur'yanova, Z h . Pzz. K h i m . , 15, 142 (1941). (4) E. N. Gur'ysnova, zbid., 21, 833 (1947). (5) Z. V.'Pushkareva and Z. Yu. Kokoshko, J . Cen. Chem. ( U S S R ) ,114, 870 (1954), (6) W. D. Kumler and I. F. Halverstadt, J . Am. Chem. Soc., 63, 2182
(1941). (7) C.%. Estok and 9. P. Sood, J . P h y s . Chem., 61, 1445 (1957).
the solution, and N z is mole fraction of the solute. Table I gives P z - , a, and b at each temperature for (8) J.-Y. Chien, J. Chem. Educ.. 2 4 , 494 (194P). (9) F. Daniels, J. N. Mathewe, and J. W. Williams, "Experimental Physical Chemistry," 4th Ed., MeGraw-Hill Book Co., New Yofk, N, Y., 1949,p. 238. (10)G. R.Leader, J . Am. Chem. Soc., 78,858 (ihl). (11) A. A . Matyott and E. R. Smith, Natl. Bur. Std. 9.) Ciro. 614, August 10, 1951. (18) G . Hedestrsnd, 2. phQe$lk. CheM., SB,428 (1829).
(u.
W. K. PLUCKYETT AND H. P. WOODS
272
solutions of each sulfonamide in benzene. In addition the dielectric constant and density of benzene a t each temperaturc indcpendently determincd for cach solution are listed. The values of a and b were detcrmined by the method of least squarrs. Dipole momcnts thcn are calculated from P 2 m by the temperature-dcpendence method by means of the equation p = (9BIc/47rN)"* ( 2) where B is the slope of the straight line obtained by plotting P2m vs. l / l ' , k is Roltzmann's constant, and N is Avogadro's number, and by the refraction method by mcans of thc cquation
=
[ 0 7 ~ / 4 ~ N ] ~ / ~ [-( PJi'r)T]'/2 2m
(3) where M r is thc molar refraction of the solute. Table I1 gives the values of B, Mr, and the dipole moments obtained for the sulfonamides by the two methods. The values of B were obtained by the method of least squares, and those of Ill, wcre calculatcd from the data of Vaughn and Seam2 The molar refractions wcre found to be independent of tcmpcraturc. /J
TABLE1 SLOPESAND INTERCEPTS OF D12-N2 A N D dn-Nn CURVESA N D POLARIZATIONS AT INFINITE DILUTIONFOR SOMESULFONAMIDES IN BENZENE AT SEVERAL TEMPERATURES 1,
OC.
a
DI
b
di
Pam,
368.2 358.9 357.2 359.8
25 35 45 55
N,N-Dimethy lmethanesulfonamide 30.8 2.274 0.40 0.8730 29.0 2.254 .41 .8622 27.6 2.234 .42 .8517 26.3 2.214 .42 .8409
482.4 464.9 452.6 441.5
25 35 45 55
N-Methylbenzenesulfonamide 30.0 2.274 0.64 0.8729 29.0 2.254 .66 .8622 28.2 2.234 .68 .8517 27.1 2.214 .67 .84OO
470.7 473.6 470.1 462.6
25 35 45 55
N,N-Dimethylbcnzenesulfonnmide 36.7 2.274 0.60 0.8730 34.9 2.254 .61 ,8622 33.1 2.234 .62 .8517 31.4 2.214 .64 ,8408
=
D1 + n'hr2'
dl2
=
dl
+ a"Nz"
(4)
(5)
TABLE I11 CALCULATED CONCENTRATIONS OF MONOMER AKD DIMER AT VARIOUS NOMINAL CONCENTRATIONS OF NMMSA IN BENZENE AT 25O. Nominal,
Monomer,
Na ( X 100)
Nz' ( X 100)
Dimer, Nz" ( X 100)
0.1034 .I340 .1766 .2196 ,2614
0.0084 .OS17 .1421 .2198 ,2914
0.1202 .2974 .4607 .6,591 .8441
584.2 568.5 5ril.9 535.9
-Dipole moment (D.) -Refraction 25' 35' 45' 58'
+ b'N2' + b"N2"
where the prime and double prime refer to monomcr and dimer, respectively. Table 111 gives the calculated monomer and dimer concentrations of NMMSA a t 25' corresponding to the nominal concentrations, N 2 , assuming the above equilibrium constant to be valid.
TABLE I1 SLOPESOF Pz,-l/T CURVES,MOLARREFRACTION, A N D DIPOLE MOMENTS OF CERTAIX SULFONAMIDES BY TEMPERATUREDEPENDENCE A N D REFRACTION METIIODS Compound
D12 and
N-Mcthylmethanesulfonamide 23.4 2.274 0.42 0.8720 22.3 .43 .8622 2.254 21.7 2.234 .42 ,8517 21.4 2.214 .42 .8409
I
addition the PZm-l/T plot for NMMSA showed nonlinear behavior. These discrcpancics are strong evidence for association for the monosubstituted sulfonamides whcre hydrogcn bonds could be formed readily. Further evidence of this interpretation may be drawn from the fact that for the disubstituted sulfonamides the dipole momcnts calculated by the rcfraction method are independent of temperature while those for the monosubstituted compounds increase with increasing temperature as would be expected with increasing monomer concentration. I n fact, Hambly and Laby'3 have reported an equilibrium constant of 40.6 l.-mole-' for the monomer-dimer equilibrium of NhSi'vTSA in carbon tetrachloride a t 25' from infrared spectra. They further state that only one association species appears to bc prcsent. With an equilibrium constant of this magnitude, appreciable dimer would be present even in dilute solutions and the dipole moment determined by conventional methods would be of doubtful significance. Assuming that the equilibrium constant of NMMSA in benzene has the same value as in CC14 and assuming that only the monomer and dimer are present, the above data may be utilizcd to calculate the individual dipole momcnts of the monomer and dimer. In this casc for dilute solutions
CC.
25 35 45 55
Molar Slope, refracB tionan Temp. ( X 10-9 (ml.) (lop.
Vol. 67
-
These expressions can be rearranged to give
and
Av.
NMMSA 2.69 23.0 2.OG 4.10 4.12 4.18 4.24 4.16 DMMSA 13.18 27.7 4.65 4.71 4.70 4.71 4.72 4.71 PiMI3SA 5.33 42.7 2.06 4.62 4.66 4.73 4.75 4.69 1lM13SA 35.73 47.6 5.07 5.12 5.13 5.13 5.13 5.13 a Thc superscript 2 on molar refraction rcfcrs to the prcviously cited reference of Vaughn and Scars.
It will be noted that the two methods give cxccllent agreement for the disubstituted sulfonamides but poor agreement for the monosubstituted compounds. In
such that plotting the left-hand side of each expression us. N2'',"2' one can obtain a' and b' from the intercepts and a" and b" from the slopes. These values may then be substituted in eq. 1 for a and b, remembering to use the proper molecular weight for the dimer, to calculate P t Z mand PttZm. From these by use of eq. 3 onc can calculate p' and p ' ' , the dipole moments of the monomer (13) A. N. Hambly and R. H. Lsby, Aualrdian J . Chem., 14, 318 (1961).
Feb., 1963
ISOTHERMAL DIFFUSION MEASUREMENTS ON THE SYSTEM WATER-PENTAERYTHRITOL 273
and dimer, respectively. These values are calculated to be: a' = 31, a" = 41, b' = 0.53, b" = 0.755, PIz.. = 808.5 cc., P"w = 1098 cc., p t = 8.2, and pt' = 7.1. The fact that when these values of a', a", b', and b" are inserted in eq. 4 and 5 the calculated Dl2 and dlz are in almost perfect agreement with the observed values indicates that the equilibrium constant in benzene has tlhe same order of magnitude as it has in CC14solution. The value of 6.2 D. does not seem unreasonable for the monomer. The value of 7.1 D. for the dimer neelds some interpretation. The most likely configuration of the dimer would consist of an eight-membered ring including two hydrogen bonds. Assuming tetrahedral bonding of the sulfur, it is seen that the methyl groups and oxygen atoms not incorporated in the ring could be arranged in either cis or trans configuration. Pre-
sumably the dipole moment of the trans form would be approximately zero, while 7.1 D. does not seem unreasonable for the cis form. If the two forms were approximately equal in concentration the dipole moment of the cis form would have to be about 14 D. to fit the data. This seems unreasonably high. It would seem, therefore, the most likely configuration of the dimer is the cis form. Presumably NMBSA would behave in a manner sirnilar to NMMSB but equilibrium data are not available for this compound. Attempts will be made t o determine polarization data and equilibrium constants for these two compounds in the same solvent and at different temperatures in order to test this theory more completely.
ISOTHERMAL DIFFUSION MEASUREMENTS ON THE SYSTEMS WATER-SODIUM CHLORIDE, WATER-PENTAERYTHRITOL, AND WATER-PEKTAERYTHRITOL-SODIUM CHLORIDE A T 25' 1 BY I;. A. WOOLF~ Department of Chemistry of the University of Wisconsin, Madison 6, Wisconsin, and the Chemistry School New South Wales, Australia Received July 9, 1963
OJ
the University of Sydney,
Some new data, are presented for mutual diffusion coefficients and refractive index derivatives of the two-component systems; partial molal volumes are reported for the system HpO-pentaerythritol. Diffusion coefficients, partial molal volymes, and refractive index derivatives are reported for one composition of the three-component system. This work presents a comparison of results obtained by the Gouy interference method and by the magnetically-stirred diaphragm cell method of studying isothermal diffusion in three-component systems.
Introduction Mutual diffusion coefficients for H20-pentaerythritol solutions have been reported by Oholm* and Lamm.* Kelly, Mills, and Stokes5 recently have given data for the mutual diffusion coefficient and the tracer diffusion coefficient of pentaerythritol in some HzO-pentaeryl,hritol solutions. Kelly6 has reported some data for four diffusion coefficients7 of two three-component systems (H2@pentaerythrito1-NaC1 and H20-mannitol-NaC1); this is the first use of the diaphragm-cell methods*vfor accurate isothermal diffusion studies in three-component systems (other than the special case of tracer-diffusion). I n the early stages of the present study, results for the mutual diffusion coefficients of the system 1320-pentaerythritol were found to difler appreciably from those of Kelly, et aL6 Accordingly, (1) The greater part of this work was supported by the U. S. National Science Foundation and by the Research Committee of the Graduate School of the University of Wisconsin from funds supplied by the Wisconsin Alumni Research Foundation. (2) Research Department, Colonial Sugar Refining Company, Ltd., Sydney, N . S. W.. Australia. (3) L. 'W.Oholm, Medd. R. Vet. aka&-Nobelinst., 2 , No. 23 (1912), cited in ref. 4. (4) 0. ILamm, lVoua Acta Regiae SOC.Sci. Uppsaliensie, 10, No. 6 (1937). (5) F. J. Kelly, R. Mills, and J. M. Stokes, J . Phvs. Chem., 64, 1448 (1960). (6) F. J. Kelly, Ph.D. Thesis, University of New England, Armidale, New South Wales, Australia, 1961. (7) The four diffusion coefficients reported by Kelly seem to be the (Dij)v considered in ref. 11. These coefficientsare different from but related to the diffusion ooefficients considered by Onsager in his discussion of phenomenalogical descriptions of diffugion in multicomponent systems: L. Onsarrer, Ann. N . Y . Acad. Xci., 46, 241 (1945). (8) A. R. Gordon, ibid.. 46, 285 (1945). (9) R. E.Stokes, J . A m . Chem. SCC.,72, 763 (1950).
extra measurements were made to cover and extend the range of concentrations studied by those authors. To check the reliability of our results, some additional measurements were made with a sample of pentaerythritollo similar to that used by Kelly, et aL6 This paper should be read in conjunction with an earlier publication'l whose general structure it closely follows. By numerous references to that paper, this paper has been considerably abbreviated : equations and references of ref. 11 which are referred to here are denoted by the suffix "W."
Experimental Materials.-Pentaerythritol (m.p. 258') for experiments 2 and 3 (Table I) and 5-8 (Table 11)was prepared by thrice recryssallizing Matheson, Coleman and Bell reagent grade pentaerythritol from water; a portion of this recrystallized sample was recrystalliied an additional two times for experiments 4,9, and 10 (Table I). The crystals were centrifugally drained between recrystallizations and before finally drying in vacuo to constant weight. Experiments 11 and 13 (Table I) were made with a sample of pentaerythritol obtained from Mills.10 Merck reagent grade sodium chloride was precipitated from its saturated aqueous solution by passage of HC1 gas. The crystals were centrifugally drained, dried in vacuo, and then fused in platinum dishes in air. (10) The author is indebted to Dr. R. Mills of the Australian National University for providing this sample which was from the same batcll of pentaerythritol as that used in the tracer-diffusion measurementB reported in ref. 5. It had been purified by vacuum sublimation of commercial gxade pentaerythritol and had 5 melting point of 260°. (11) L. A. Woolf, D. a.Miller, and L. J. Gosting, J. A m . Chem. Xoc., 84, 817 (1962).
