甲基丙烯酸甲酯、甲基丙烯酸乙酯与酚络合的介电驰豫行为 甲基丙烯酸甲酯、甲基丙烯酸乙酯与酚络合的介电驰豫行为

甲基丙烯酸甲酯、甲基丙烯酸乙酯与酚络合的介电驰豫行为

  • 期刊名字:物理化学学报
  • 文件大小:316kb
  • 论文作者:LIAKATHALIKHAN Faize,SIVAGURUN
  • 作者单位:Department of Physics
  • 更新时间:2020-10-26
  • 下载次数:
论文简介

物理化学学报( Wuli Huaxue Xuebao)AprilActa Phys. -Chim. Sin, 2007, 23(4):513-516513[Article]www.whxb.pku.edu.cnDielectric Relaxation of Methyl Methacrylate and EthylMethacrylate on Complexation with PhenolsLIAKATHALIKHAN Faize *SIVAGURUNATHAN Periyasamy(Department of Physics, Annamalai University, Annamalai Nagar, Tamil Nadu 608 002, India)Abstract:Dielectric absorption studies of H-bondedmethacrylate (EMA) with p-cresol, p-chlorophenol, 2,4-dichlorophenol, and p-bromophenol were studied at microwavefrequency 9.37 GHz in dilute solution of carbon tetrachloride at 308 K. Different dieletric parameters like dielectricoptical frequency were determined. The validity of the single frequency equation of Higasi et al. for multiple relaxationtime To was found to be a function of the hydrogen bonding strength of phenolic hydrogen, whereas the group rotationrelaxation time T2 was a function of the steric interaction of proton donor. The relaxation time was the maximum at 50:50 (molar ratio) of methacrylates with phenols.Key Words: Acrylic esters; Phenol derivatives; Delectric relaxation; X-band microwaveDielectric relaxation behavior of mixtures of polarbonding between free hydroxyl group of phenol and the car-boxyl group of ester using the dielctric method. This study isture, and environmental factors has evoked considerable interest.expected to provide better understanding of the nature of mole-On the basis of the results, models of relaxation process in liquidcular orientation process.mixture have been formulated. The dielectric investigation ofhydrogen-bonded compounds in non-polar solvent provides1 Experimentalvaluable information regarding molecular complex formation inThe static dielectric constant (e0) was measured using thesolution. Rewar and Bhatnagar!" have reported the dielectricheterodynebeat methodproperties of butyl acrylate, butyl methacrylate, and iso-butylment, Dipolemeter DM 01 supplied by Wissenschaiftlich Tech-methacrylate in the microwave region at different temperatures.nische Werkstatter, Germany, operated at 220 V. The refractiveKhanna and Sobhanadril21 have studied the dielectric relaxationbehavior of methyl acrylate, ethyl acrylate, methyl methacrylate,surements of wavelengths in the dielectric and voltage standingand ethyl methacrylate in the pure liquid state at four differentwave ratio (VSWR) were made at 9.37 GHz using a slotted linefrequencies. Dielctric parameters for dimethyl formamide-phe-and short circuiting plunger.nol and dimethyl acetamide. phenol were reported by Tucker etThe calculations of dielectric constant at an angular fre-al.3l. Recently the research groupl4-91 investigated the complexquency (e') and dielectric loss (e") were made following theformation of acrylic esters with proton donors (alcohols) in non-method of HestonlO adopted for short- circuited termination. Thepolar solvents using the FTIR spectroscopic method. The studyaccuracy of measurement of E' and 8" is土1% and +5%, respec-of the H-bonds of the type 0- H..O= C occupies a position oftively. The viscosities were measured with the help of Oswald'sconsiderable importance as it relates to the study of biopolymers.viscometer. The temperature of all these measurements wasThus, the study and knowledge of dielectric properties of themaintained at (308.0+0.1) K using a water circulating thermostat.ternary mixtures of acrylic esters with polar associating liquidsE. Merck variety of methyl methacrylate (MMA), ethyl meth-in non-polar solvents is expected to provide useful and vital pro-acrylate (EMA), and 2,4-dichlorophenol, distlledl samples of p-cresol, p-chlorophenol, and recrystallized p-bromophenol wereof industrial interest. Keeping both the industrial and scientificused. The physical parameters of all the chemicals used haveinterests in mind, this study attempts to investigate the hydrogenbeen checked against their literature values.Received: October 8, 2006; Revised: November 17, 2006; Published on Web: March 12, 2007.中国煤化工English edition available online at www sciencedirect.com*Corresponding author. Email: shamisardar@ yahoo.comMHCNM HGC Editorial office of Acta Physico-Chimica Sinica.514Acta Phys. -Chim. Sin., 2007Vol.23The proton donors (phenols) and the acceptors (MMA andments, and W2 is the mass fraction of the solute.EMA) under study were separately dissolved at the same molarThe molar free energies have been calculated using theconcentration (0.3 mol.L-) in the solvent carbon tetrachloride.Eyring' s equation as:Their dielectric constants were measured separately. Then ther=(h/kT)exp(OF,IRT)two solutions were mixed in different proportions but with then=(Nh/V)exp(OF,/R7)total concentration maintained at a fixed value and were subject-where, h is the Plank s constant, k is Boltzmann' s constant, N ised to the dielectric constant measurements. As the maximum de-Avogadro number, and V is the molar volume, and OF, and OFviation of the dielectric constant for all the studied systems oc-are the molar free energies for the dielectric relaxation processcurs at an equimolar ratio of the solutes, it is presumed that theand the viscous flow process, respectively.deviation is due to the formation of only 1:1 complexes.3 Results and discussion2 Evaluation of the dielectric parametershe termary systems selected were alkyl methacrylatesAccording to Higasi mtlh112, the average relaxation time(MMA and EMA) with proton donors (p-cresol, p-chlorophenol,Ta is described by2,4-dichlorophenol, and p-bromophenol) using carbon tetrachlo-Tn=a'"lw(a'-ax)ride as the solvent. The value of relaxation times T()> T2) for allwhile the overall dielectric relaxation T2) is given bythe systems were calculated using the Higasi' s method and areT2=(a-a' )/wa"(2) shown in Tables 1-2. It is observed that the value of relaxationtimes T(r T2) increases with increasing chain length of methacry-To=V TnT2)lates and acidity of phenolsl3.131. The increase in relaxation timeTo) may be called the mean relaxation time, where w is the angu-may be due to the increase in effective radius of the rotating u-lar frequency, an a', a", and ax are defined by Eq.(3)nit. The observed higher value of EMA can be attributed to theε=Em+aqN2ε'=s;+a'wz .(3)In these systems, the complex formation is likely to occur be-e"=a"w2tween H°+ of phenols and 0- of C=O group of ester. Oxygenin which subscript 1 refers to the pure solvent and subscript 2voids available for O- -H to penetrate and enter into complexa-refers to the solute, subscript 0 refers to the static frequency,tion and also provides information regarding the hydrogen bondsubscript∞refers to the infinite or optical frequency measure-Table 1 Values of dielectric constants and relaxation times for various mass fractions ofmethyl methacrylate with phenols in carbon tetrachlorideRelaxation time (ps) (using Higasi's method)PhencMole ratio of MMA and phenolεTm_TaTmp-cresol .13.021 2.498 0.148 2.622 2.22811.7814.1512.911:20.0232.51215.6717.2116.430.025 2.523 0.236 2.8922.23419.5826.4022.33:12.4872.8112.23518.4324.3221.520.029 2.451 0.217 2.718 2.23717.2320.7819.27p-chlorophenol1:0.0272.4720.1622.64716.1918.2417.180.028 2.488 0.205 2.792 2 23722.6323.800.0312.508.2222.8792.225.5825.792:12.4782.80826.160.0342.446 0.204 2.732 2.24520.09 .21.232,-dichlorophenol2.4712.6522.23013.4115.8414.570.0232.453 0.178 2.667 2 23216.6120.4918.451:10.0262.468).2412.78919.7622.4921.080.028 2.453 0.236 2.745 2.23619.0720.8919.904.432.2332.7222.23818.2221.0218.59p-bromophenol1:32.45616.9719.740.027 2.462 0.223 2.839 2 23923.1028.5525.682.4513.22933.220.031 2.446 0.312 2.946中国煤化工26.37;:1.0332.4220.233 2.7612.YHCNMHG24..No.4LIAKATHALIKHAN Faize et al. : Dielectric Relaxation of Methyl Methacrylate and Ethyl Methacrylate515Table 2 Values of dielectric constants and relaxation times for various mass fractions ofethyl methacrylate with phenols in carbon tetrachlorideRelaxation time (ps) (using Higasi 's method)Phenol .Mole ratio of EMA and phenol8.p-cresol:30.0232.422 0.179 2.590 2 23213.615.8514.69120.0252.6876.3019.7717.95:10.027 2.503 0.227 2.893 2 2360.4629.4623.94:0.0292.475 0.211 2.8222.220927.7824.13;:10.0312.7582.240p-chlorophenol0.029 2.436 0.168 2.633 2.23717.719.8019.29:22.457 0.195 2.7852.23823.3528.4025.750.0323.12036.5129.940.033 2.421 0.213 2 8332.24323.932.6627.990.035 2.411 0.204 2.785 2.24424.7830.9627.342.-dichlorophenol0.0242.5982. 2356.8918.8117.820.026 2.472 0.191 2.752 2 2373.02248821.18;10.027 2.521 0.289 3.101 2.24223.1333.8327.970.0282.489 0.2432.9112.24321.829.3225.300.032 2.443 0.226 2 8222.2 460.1928.1123.91p-bromophenol30.032 2.378 0.168 2.613 2.23721.3323.6222.450.0332.394 0.1952.78525.7433.8629.510.035 2.469 0.253 3. 1252.243 .33.3:43.7838.230.037 2.433 0.213 2.865 2.24529.9734.2532.040.0382.426 0.2042.8172.24726.32.3729.17between interacting components.ular association between alkyl methacrylates (MMA and EMA)Carbon tetrachloride is a symmetrical and a non-polarand phenols is a maximum at 50:50 (molar ratio) and then decreas-molecule. But each chlorine atom in this molecule is highly po-es at other molar ratio. From this, it can be concluded that the 1:larizable due to its three lone pair of electrons and therefore it1 complex is dominant in alkyl methacrylate-phenol systems.can function as an electron donor. There is, therefore, a possibil-The relaxation time T increases with the increasing acidity ofity of interaction between the positive hydrogen of hydroxylproton donor in complex systems. But in alkyl methacrylatesgroup and a chlorine atom of the carbon tetrachloride molecule.(MMA and EMA) with 2,4-dichlorophenol sytems, the relax-The potential hydrogen bonding nature of the carbon tetrachlo-ation time values are less than other phenol complexes due toride molecule maylaxation timel4. It has been found that two opposing effects, name-The molar free energy of activation for viscous flow△F,ly specific interactions between C= O group of ester and - -OHand the free energy△F, are calculated and are shown in Table 3.breaking of intermolecular hydrogen bonds in phenols are possi-in agreement with the fact that the process of viscous flow,bly operative in these mixtures. The relative size of both esterwhich involves both the rotational and transnational forms ofand phenol molecules determines the predominance of a particu-Table 3 The activation energies at 1:1 stoichiometriclar type of interaction over the other. The results show that theratios of methacrylate + phenol systems inrelaxation time is larger at 1:1 molar ratio of methacrylates withcarbon tetrachloride at 308 Kphenols. The relaxation time decreases conspicuously for theother molar ratios but are higher than either of the components.Activation energySystemSaxena et al.l9s studied the H-bonding in some carbonyl+phe-SF./(kJ.mol") AF,/(kJ.molr)nol derivative systems in different compositions. It was also ob-methyl metaryatet+p-cresol12.481296served that the relaxation time of termary mixtures is alwaysmethyl methacrylate+p-chlorophenol13.7414.08much greater than either of the polar solutes in the inert solvent.methyl methacrylate +2,4-dichlorophenol12.6612.89The relaxation time for dilute solution of p-cresol, p-chlorophe-methyl methacrylatetp-bromophenol14.0514.68nol, 2,4-dichlorophenol, and p-bromophenol observed in theethyl methacrylate+p-cresol12.8813.12present study ranges between 14 and 35 ps, with excess of phe-ethyl methacrylate+p-chlorophenol14.27nols, the relaxation time of methacrylate+phenol system shows aslight increase. This result is in agreement with the earlier inves-ethyl methacrylate+2.中国煤化工13.19tigations of Tucker et al.5I. The result also shows that the molec-ethyl methacrylate+pMYHCN MH G-.516Acta Phys. -Chim. Sin., 2007Vol.23the alkyl chain length of methacrylates and acidity of phenolsplay significant roles in the determination of dielecric propertiesRof the above-mentioned systerms that were studied.- R2References1 Rewar, G. D; Bhatnagar, D. Ind. J. Phys, 2001, 75A(5): 541Fig.1 Hydrogen bonding interaction between phenols2 Khanna, R. K; Sobhanadri, J.J. Plhys. D: Appl. Phys., 1972, 5:and alkyl methacrylates (MMA and EMA)R=CH。R=CH, for methyl methacrylate;3 Tucker, S. w; Walker, S. Trans. Faraday Soc. (GB), 1966, 62:R=CH。R=CH。for ethyl methacrylate;2(Sivagurunathan, P.; Dharmalingam, K.; Ramachandran, K.Ar-- CH,for p-eresol;Ar--(_ y-I.or pchoropbeol;5 Sivagurunathan, P.:; Dharmalingam, K.; Ramachandran, K. Ind.) Cl,for 2,4-dichlorophenol; Ar。》BK, for p-bromopleolJ. Pure Appl. Phys, 2005, 43: 9056 Sivagurunathan, P; Dharmalingam, K.; Ramachandran, K. Mainmotion, faced greater interference from neighbors than dielectricGroup Chemisty, 2005, 4: 241relaxation, which takes place only by rotation!l. Smyth et al."7]7 Sivagurunathan, P; Dharmalingam, K:; Ramachandran, K. Phys.pointed out that the relaxation time of a proton donor increasesChem. Liq., 2006, 44: 778as the acceptor ability of the solvent environment increases.Sivagurunathan, P.; Dharmalingam, K: Ramachandran, K. Ind.Similarly, for a given proton acceptor, the relaxation time mustJ. Phys., 2005, 79: 1403increase with the proton donating ability of the donor solute. The9 Sivagurunathan, P.; Dharmalingam, K; Ramachandran, K.results are in accordance with this conclusion.Spectrochim. Acta A, in pressIn the present systems that were studied, it was observed10 Heston, W. M.; Franklin, A. D.; Hennelly, E. J; Smyth, C. P.that the relaxation time of termary mixtures (alkyl methacrylatesJ. Am. Chem. S1950, 72: 3443with phenols in carbon tetrachloride) was much greater than the11 Higasi, K; Koga, Y; Nakamura, M Bull. Chem. Soc. Japan,1971, 44: 988binary mixture (phenols with carbon tetrachloride or alkyl2 Sivagurunathan, P:; Dharmalingam, K; Ramachandran, K;methacrylates with carbon tetrachloride). This result indicatedKalamse, G. M. Acta Phys. -Chim. Sin, 2007, 23(1): 50the formation of hydrogen bond between the hydrogen atom in3 Sivagurunathan, P; Dharmalingam, K; Ramachandran, K. MainO- -H group of phenol and oxygen atom in C= O group of alkylGroup Chemistry, in pressmethacrylates (MMA and EMA) and is shown in Fig.14 Srinivasan, N; Kumar, s: Krishna, s. Ind. J. Pure Appl. Phy,2003, 41: 8764 Conclusions5 Saxena, s. K; Saxena, M. C. Ind. J. Pure. Appl. Plys, 1981, 19:550 .The hydrogen- bonded complexes of alkyl methacrylates6 Kalaivani, T.; Kumar, S.; Krishnan, s. Ind. J. Chem, 2004,(methyl methacrylate and ethyl methacrylate) and phenols (p-43A: 291cresol, p-chlorophenol, 2,4-dichlorophenol, and p-bromophenol)17 Smyth, C. P.; Ratajczak, H; Orille-Thomas, w. J. Molecularhave been studied in dilute solution of carbon tetrachloride usinginteractions. Vol. II. New York: Wiley, 1981the dielectric method. From this study, it may be concluded that中国煤化工MYHCNMH G.

论文截图
版权:如无特殊注明,文章转载自网络,侵权请联系cnmhg168#163.com删除!文件均为网友上传,仅供研究和学习使用,务必24小时内删除。