Mehrotra, N K

Misra, S B L

Mitra, S C

Somevanshi, S K S

IACS Institutional Repository

Study o f dielectric relaxation mechanism and mutual viscosity in some substituted anilinesS. K. S. SoMSVANSHi, S. C. Mitba , S. B. L. Mtsba and  N. K. M bitbotbaPhysics Department, Lucknow University, Lucknow (RecpAved 5 April 1977, revised 18 June 1977)Indian J. Phya. SOB, 142-148 (1978)Tho prcKSont communication reports the relaxation times and mutual vistjosity of dimethyl aniline; N-ethji aniline; N-N-dimethyl aniline; 0-ot\iy\ aniline; benzyl aniline and N-ethyl-6?-toluidine in dilute solutions of iKmzene at 3-13 cm wavelength (9585 MHZ) in microwave region, and at three temperatures 20"*, 30° and 40°C. Correlation of mutual viscosity with relaxation time leads to the conclusion that the mutual viscosity is a better representation of the resistance to the rotation of the individual solute molecule. The molar free energies, the entropies and the enthalpies of activation have also been evaluated and compared.1. IntboduotionThe discripancy botwo(>-n tho observed values and the calculated values (using Debye equation) of relaxation time can be explained by using instead of solvent viscosity a mutual viscosity paramotor derived by Hill (1954) and dis­cussed in an earlier paper (Mehrotra 1971) by one of the authors. The average intermolocular distances i.e., <r’s have been determined using the expressions as giv<m in tho paper (Mehrotra et al 1969).It is interesting to not.e that an expression involving mutual viscosity para­meter 1^2 was also proposed by Vaughan et al (1961). The results obtained using tliis expression arc in good agreement with those obtained using Hill’s equation (1954), also discussed in the earlier paper (Mehrotra 1971).Kalman & Smyth (1961) found that the equationwhere a =  AHr/AH?; which could bo derived by using rate equations, gives satisfactory results over a small temperature range. However, they did not examine it for large number of compounds.In the pre.sent investigation we have employed tho above relations and undertaken a comparative study using the macroscopic viscosity term the average mutual viscosity term i/i, aaid Kalman’s viscosity parameter The142Stvdy of didectric rdaxaiion mechanism 143results* obtain€Ki indicates that Kahnau’H equation gives a closer relation bet>\ot>n viscosity and relaxation time. However, the average mutual viscosity givi s^ a still better correlation between the phenomena of relaxatiion and viscosity.The free energies of activation for the proijoss of dipole orientation and viscous flow have also been calculated using Eyring's equations (1941).2. ExpebIMentalsThe dielectric relaxation times have teen determiiu^l using tb,e fixiui fre­quency mothcxl o f Go£>ala Krishna (1957|f for dilute solutions. Thc^  standing) wave tochniqite o f Roberts & Von Hippie measim^-mont o f dielectric constant e* and tJie Joss factor e" required lor tJie calculation o f r.The viscosities were determined with the help o f Hojiy^k'r’s jinHusion visco- meter to an accuracy o f ± 2 % .All the compoimds ustKl ar<^  of pur<» quality, ohtaim^ from Mossis. Britisli Drug House, Purest quality analar benzene obtaiiuKl from Messrs. B. D. H. was distilled before use.S. R esults and Discussions(i) Relaxation TimeTho dielectric constant e' and loas e" for tlu> ooinpamds at various con­centrations and temperatures an* giv(*n in table 1. Th(* values of tho relaxation time T, tho mutual viscosity »/ia and tlic ratios JV/i/,, arid ir/? /, au*reported in table 2. Tho values o f relaxation times and molar activation energy parameters at different temperatures are given in table 3.Tho relaxation time o f <?-othyl aniliiu* is found to be greater than that of N-ethyl aniline, although the si^e o f both the mol.smk»s arc approximately the same. This may be explained due to greater steric hitiderance expeneneed by the rotating -NH^ gioup by th.* neighbouring ethvl group at the ortho-positionin the formt^r moloculo.The relaxation times o f dimethyl aniline and N-N-dimethyl aniline are of similar magnitude and arc consistent mth tho sizes .of the molecules.INitther tho relaxatitm time of N-othyl-^i-toluidine is much larger than that o f N-etKyl aniline ^hich. is not only due to the bigger size o f the former molecule but atoe due to the greater hindorance produced by the methyl group attached at the ortho position to the rotation of-NH* group in the former molecule.Benzyl anUine has largest value of the relaxation time as compar,^ to all other compounds investigated which may be partly due to the l**^*^* ^tho molecule and partly due to maximum hinderanco offered by phenyl gr p to intramolecular rotations of tho amino group.144 Somevanshi, Mitra, Misra and Mehrotra(ii) Correlation of Dielectric Relaxation Times and Viscosity ParametersTho intordoix^mlonce o f tho dioloctrii; rolaxation time and the viscosity factors has boon studied by apjdying various equations. Tho values o f  different viscosity parameters are listed in table 2  together with the values o f  relaxation time.Table 1. Diolendric constants c' and losses of compoundsConoentrationW20"C 40^ COOJ870-02040-02670-02710-03252-23462-13092-20952-20962-201HDimethyl Aniline0-021860-029600-046860-047080-085522-23722-20822-20182-18492-10580-019870-021930-050500-037180-078192-25522-10752-19672-18472-17190-018330-023760-049870-033930-07261N-N-Dimethyl Aniline0-01700-02130-02400-02890-03152-16042-17191- 95252- 2056 2-17970*071530-078770-050760-077170-088382-21332-13732-21332-20822-19520-066000-075830-058760-064280-067592-17322-20172-18742-19622-19010-062040-064550-102090-045860-065490-02950-03400-03780-04120-04512-15132-16022-20032-20942-1913N-ethyl aniline0-037710-045610-041980-107960-118502-15262-19772-20302-21072-22510-034960-039730-034720-071250-056172-17322-29912-20432-21202-24500-030080-041720-013460-128300-062130-01640-02120-02760-03050-03492-14762-18922-19432-21122*2283^•ethyl aniline0-018470-018720-036750-039340-042942-19052-20222-20082-17372-18780-015750-018590-024780-012520-034502-19562-20482-20732-20482-19790-016030-071440-024460-028530-03387N-ethyl - 6- toluidine0-02620*03140-03630*03950-04342-15392*16422-17322-18092-17450-01840-04300*04990-05000*05232-15522-16552-16552-18222-17710-03460-03520-04770*04920-05612-15782-16802-14372-18612-18090-03010-03200-04640-04740*05010-01220-02310-02860-03260*03832-11182-15002-15022-15912-17840-01780-01790-03780-03830*0392Benzyl aniline2-1284 2-1539 2-1245 2-1655 2-17190-01220-03280-03430-03490-03692-13832-14752-15612-14332-16030-03250-03070-03390-03690-0773Siydjf of dtdectfie reUixcUion mechanism 145IrSatOo8rsi  ieO (>l - sc8 03C3>b 5.a ^“S£ - -^  m5■f<N©IXo>o<905<NlO05op© f—4*?COo oCO©0404t-PHl> ©XXQC^04 04 XpHt;-©pH904COCO 5 ©'pfiCO COl-H lb cbiH cb•H 05 6 pH 04 «T04 cb04 04 cb04 eo i Xeo&Xo»olO QOOOOoCOCO00lO00r-COCO©OO©<Nt-p—4oCO 1r«<x>ooCO SCO a>pH©CO©COoeo0S4 sCO©r-CO^11CO CO 6CO cbCO cbCO 00CO 05<N ©© ii s © 0500 cb© cb© lb© 04X cbX XX>1 ^^ 1 ??•XmS ' ©eo © © 04pH 04© ©X tilX ©© ©© ©© ©X 04 ©X © © gn !>• t» © © © © © © t'- © © © ©O © © © © © © 05 © © © © © © © ©&§1Iot-* l> X pH X © 04 X ^  X pH X © X © © © 0404 04 © © © 04 rf< 1" © X pH © X© © © CO © © © © cp 9 XPH cb cb 05 cb cb cb ® X 64 lb X cb «<—4 cb X ©X -•o* Tt< X X © © © t> X o Xo o  ^< »0 ffO t- (M<D «0 QO05 l> «b(N fH pHS 500 o QOCO <NCO6X0>lr—©© ©t-© ©b-X©©04©©1"© X©X©©©Xt-©Xr- 4^t-©1-©1—< Sr-CO©©X© 3 04©6 6 6 6 6 6 6 6 6 6 6 6 © 6 6 © 6 604©© s©Xo©04©© ©©X©©04©© ©©X©©04©CO ©©Xg04©© sXs04©© 3©X©©© © 6 6 © © © © © © 6 © © © © © © 61 X X © X pH pH o © © X © 04 © pH2 « cp © X *7 9 X © t;- © r» X © CO © o CO ©XMS© cb l> cb cb cb cb cb © © ob © pH cb cb cbA. 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O (N 01 01 »o © 10 CO CO CO r- r- 1- tH Tji.  ^ 2  fl<J V -© © © 9 © © © © © •H rH rH © © © pHliH CM CM CM i—t pH i-H C^J OI C^l OI C^l ©4 OI CM(4H0w i’I'l r- © 10 CM © CO CO CO OI ©fc. 2a <  x | -© o © 9 rH © © »H © © © © 9 op © ©ocb cb 04 cb cb CM cb cb cb cb cb 04 cb cb CM OI CMe«c6 CO <1/P h wt 1 o <M © OI © 04 © 04 Tt< © 04 © 04 rt’<1 x;:^©Ol©OI©OI©CM©CM©CM© ©C^J©CM©OI©CM©OI©CM©CM©C?1©CM©CM©CM§G M ” lO © © CO r* CO © © CO © OI CO o © t'- IH COCO CO tT CM CO CO CM OI © © © I-1 CN OI CM CM OI CM OI <N 04 04 04 CM C^4 04 CM CM1 n©  . CO •tt CO © CO pH r» pH © © © CO © CM © pHO CO © op © op © 1;- ip t'- © © CO © 9 Cp ©V^ c c © cb cb cb cb cb cb © © cb © cb © cbs IH pH pH rH pH pH pH'dpce©|w CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO5 ®  . © © © © © © ® © © © © ©a H (N CO CO ©4 CO CO OI CO CO 04 CO CO CM CO CO OI CO CO• m4•M1q6 £CO«1a11§1 1 11rS*3'o 11f©1Oj iQ1 1“os19IStudy of dielectric relaxation mechanism 147It is apparent from table 2 tliat tl\o ratio Trlrfi increases witli, tJie rise in temperatures for nearly all the compounds investigated wJiicli is not in confoi mity with the Debye tlieory which requires the ratio to be constant for tlu> compounds of same size for small change in temperature. This anomaly can be explained if the Kalmann viscosity parameter is used in plaa> of g/j, where the varia­tion in the values of ratio bt^ jornoS Small as comparenl to the values ofthe ratio at different temperatun^s. Further if g/jg i e., the mutual vis­cosity of tile solute and th,e solvimt is uschI instead of iji and ?/i* the variation in the values o f tJie ratios Trjijy^  at difftirdnt temperatures is negligibly small and this leads us to conclude that gives a more convincing aiicount of tJui resistance confrontcKl by tlie individual solute molecules during tlie process of rotation. Tlie valui s^ of the aV(trag<Hi mutual viscosity" for diffenmt solutions as determined from equation of Vaughan ei al (1961) are almost equal to those of the corresponding mutual viscositi(.*S determined fiom tlie liquation ol Hill (1954). This is probably due to tlie fact that form of equation of Vaughan et al is very nearly the same as that of equation of Hill wliicli has also bmui ])ointed out by Vaughan et al (1961).(iii) Ther7nodyruimic ParametersJt is ovidoni from table 3 tJiat the free t>nergy of activation for the visi.ouH flow process is always groatc^ r tl a^n that for tlie dielectric relaxation process in all th*» cases investigated. This is in agnsmiont with th(* fact that wliilc the process of dipoh, orientation involves only tlu^  rotation of the inok*eules, the process o f viscous flow invo)v,»s both rotation and translation. Similar results were obtainwl (earlier by one of thi* authors (Melirotra 19(57) in th.- ease ot sub- stitutod pyt idines.AoknowledgemkntThe authors aic deeply indebtcsl to Dr. M. C. Saxena, Reader, Physics Department for his keen interest and encourage^ment through out the work and the Chemistry Department ibr kind assistance during the wr^k. Wt> am also grateful to Di. B. G. Gokhale, Head of th.e Department of Physics, Lucknow University, for providing necessary facilities.R efekencesDebye P. 1929 Polar Chemical Catalogue Company. New York, 90.i n -  T ^ y r t 7 n T . u 7 l .  T , ^  Of Proceaae. Mc-Oraw HillGlaestone 8.. Laidler K. J. & Eyr g Company, Inc.. New York, N.Y. p. 648.148 S om evaB sh i, M itra , M in a  a n d  M e h ro traHill N. E. 1964 Pm. Phyt. Soc. 67.140.Kalmann 0. F. & Smyth C. P. 1961 J. Am. Chem. Soc, 88. 671.Mehrotra N. K. k Saxena M. C. 1967 BuU. Chem, Soc, Japan 40.19.Mehrotra N. K., Pant T. C. k Saxena M. C. 1969 Trans. Paraday Soc. No. 660, Pt. 8, 66. Mehrotra N. K. 1971 Ind. J. Phys. 45, 83.Boberte 8. k Von Hippel A. 1946 J. Appl. Phys. 17,610.Shukla J. P., Shukla D. D. k Saxena M. C. 1969 J. Phys. Chem. 73, 2187.Vaughan W. E., Purcell W. P. k Smyth C. P. 1961 J. Am. Chm, Soc. 83.671.

Study of Dielectric Relaxation Mechanism and Mutual Viscosity in some Substituted Anilines

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Study of Dielectric Relaxation Mechanism and Mutual Viscosity in some Substituted Anilines

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