Journal of Chemical and Pharmaceutical Research, 2012, 4(1): Research Article

Available online wwwjocprcom Journal of Chemical and Pharmaceutical Research, 2012, 4(1):901-912 Research Article ISSN : 0975-7384 CODEN(USA) : JCPRC5 Solvent Effect on the Stability Constants of Charge Transfer Complexes of Iodine and Certain Ethers at 303 K S J Askar Ali 1 *, P A Abdullah Mahaboob 2 and M NizamMohideen 2 1 PG and Research Department of Chemistry, The New College, Chennai, India 2 Department of Physics, The New College, Chennai, India ABSTRACT Ultrasonic velocity (U), density (ρ), and coefficient of viscosity (η) values are measured for solutions containing iodine and one of the following ethers in equimolar concentration in the range 0001-001M at 303 K Diphenyl ether, 4-chloroanisole, anisole and 1,4-dioxane are used as donors Dichloromethane, chloroform, carbon tetrachloride and n-hexane have been used as solvents Acoustical parameters such as adiabatic compressibility (β), absorption coefficient (α/f 2 ), internal pressure (π i ) and cohesive energy (CE) values are calculated from the values of u, ρ and η The trend in the acoustical parameters establishes the formation of charge transfer complexes between iodine (acceptor) and ethers (donors) The formation constants (K) are calculated for these complexes The free energy of formation of these complexes ( G) are also reported Attempt has been made to correlate the formation constants with polarizability (α), dielectric strength (ε) and dipole moment (µ) of the donor and solvent molecules The free energy of activation ( G # ) and viscous relaxation time (ד) are found to be almost constant for these complexes indicating the formation of similar charge transfer complexes in these systems Keywords: Solvent effect, formation constants, donor-acceptor complexes, iodine, ethers, ultrasonic method INTRODUCTION Ultrasonic velocity measurements have been successfully employed to detect and assess weak and strong molecular interactions, in binary [1-5] and ternary [6-11] liquid mixtures These studies can also be used to detect complexation and for the evaluation of stability constants of complexes [12-14], in particular the charge transfer complexes formed between organic compounds containing electron rich centers and electron deficient compounds Ethers are Lewis bases as they contain electron rich ethereal oxygen and thus they can function as donors Among halogens, iodine has basic character and it can function as electron acceptor It forms charge transfer complexes with electron donors [15] In the present work, charge transfer complexes are detected between iodine and ethers in four different solvents by ultrasonic method and the stability constants of these complexes are calculated using modified Bhat equation [16] In this paper, we report the results obtained in the ultrasonic study of molecular interaction between iodine and four ethers namely, diphenyl ether, 4-chloroanisole, anisole and 1,4-dioxane in dichloromethane, chloroform, carbon tetrachloride and n-hexane at 303K These studies are made mainly to investigate the influence of structure of donor molecules and polarity of medium on the stability of this type of complexes and the factor which plays significant role in the complexation 901

S J Askar Ali et al J Chem Pharm Res, 2012, 4(1):901-912 EXPERIMENTAL SECTION Materials Iodine (Merck-GR) was purified by sublimation The solvents dichlromethane (bp 313 K), chloroform (bp 335 K), carbon tetrachloride (bp 350 K) and n-hexane (bp 341 K), are distilled before use The four ethers diphenyl ether, 4- chloroanisole, anisole and 1,4-dioxane used as donors are of AnalaR grade (SDS) Accurately weighed amounts of donors and acceptor were dissolved in suitable solvent to obtain solution in the concentration range 1x10-3 - 1x10-2 M Methods Ultrasonic velocity measurements were performed with ultrasonic interferometer (Model F81) supplied by Mittal Enterprises, New Delhi operating at a frequency of 2 MHz It has an accuracy of ± 01 ms -1 Viscosities of pure compounds and their mixtures were determined using Oswald s viscometer calibrated with double distilled water The densities of pure compounds and their solutions were measured accurately using specific gravity bottles with accuracy of 0001 kg/m 3 The temperature is maintained constant at 303 K with a precision of ± 01 K with a thermostat The ternary liquid mixtures containing n-hexane, equimolar concentration of donor and acceptor are thermostated at 303 K for 30 minutes before measuring ultrasonic velocity to attain equilibrium Acoustical parameters such as adiabatic compressibility (β), absorption coefficient (α/f 2 ), free length (L f ), internal pressure (π i ), cohesive energy (CE), relaxation time,(ד) stability constant (K) and the thermodynamic parameter free energy change ( G) for the complexation and free energy of activation ( G # ) were calculated using standard equations [15-20] RESULTS AND DISCUSSION The measured ultrasonic velocities, densities and viscosities at various equimolar concentrations of diphenyl ether, 4-chloroanisole, anisole and 1,4-dioxane with iodine in dichloromethane, chloroform, carbon tetrachloride and n- hexane at 303 K are given in Tables 1 3 The plots of ultrasonic velocity vs concentration of four ethers in four different solvents are presented in Figs1-4 From the plots it is seen that the ultrasonic velocities vary non-linearly with concentration for all the sixteen systems At a characteristic concentration, the ultrasound velocity of solution is less than that of ideal mixing indicating the formation of charge transfer complex between the donor and acceptor The ultrasonic velocity is minimum at characteristic concentration indicating that the extent of complexation is maximum at this concentration This concentration depends on the system There is decrease in density (Table 2) at a specific concentration (3x10-3 - 6x10-3 M) and this also suggests that the complexation is concentration dependant This is also supported by the trend in the viscosity values (Table 3) The adiabatic compressibility is a measure of intermolecular association between the donor and acceptor The plots of adiabatic compressibility vs concentration of four ethers are given in Figs5 8 From these plots, it is evident that there is considerable variation in adiabatic compressibility values in the concentration range 3x10-3 9x10-3 M indicating that the complex formation is significant in this concentration range The calculated absorption coefficient (α/f 2 ), internal pressure (π i ) and cohesive energy (CE) for all the above systems are given in Tables [4-6] The absorption coefficient (α/f 2 ) generally increases with increase in concentration and this trend suggest that the extent of complexation increases with increase in concentration The internal pressure (π i ) is a measure of cohesive forces between the constituent molecules in liquids In order to assess the cohesive forces in the ternary liquids investigated; π i values are calculated for all the systems (Table 5) It is found that the internal pressure in ternary solution is generally greater than that of pure solvent which shows that the intermolecular attractive forces between the molecules of components are strong in solution Further, the internal pressure for a given system increases with increase in concentration which suggests that there is an increase in the extent of complexation with increase in concentration The stability constants are calculated from measured ultrasonic velocities using modified Bhat equation [16] These values for all the donor-acceptor complexes are given in Table 7 It may be noted that the stability constant values are almost constant for a given system at a given temperature but are different for different donors indicating that the equilibrium constant depends on the structure of ethers By comparing the values of equilibrium constant of four ethers in one solvent, the ease of complexation with iodine and ethers is found to be in the order of diphenyl ether > 902

S J Askar Ali et al J Chem Pharm Res, 2012, 4(1):901-912 4-chloroanisole anisole > 1,4-dioxane During complexation between ether and iodine, ethereal oxygen being electron rich donates electron which is attracted by positive end of iodine molecule Diphenyl ether contains electron releasing phenyl groups on either side of the donor atom and similarly in 4-chloroanisole, chlorine atom in the para position to methoxy group releases electron by mesomeric effect But in anisole molecule the resonance effect is limited although methoxy group is directly attached to a phenyl ring In dioxane molecule, absence of mesomeric effect is the reason for the least stability constant value From the stability constants obtained for the above systems, the free energy of formation ( G) are calculated at 303 K and they are given in Table 7 For all the systems, G values are negative indicating that the charge transfer complexes are thermodynamically stable The free energy of activation ( G # ) and relaxation time (ד) are intrinsic properties of a charge transfer complex Since similar complexes are formed in the four systems these two properties are almost constant Table 1 ULTRASONIC VELOCITY (ms -1 ) VALUES OF IODINE - ETHER SYSTEMS IN DIFFERENT SOLVENTS AT 303 K Conc Diphenylether 4-chloroanisole anisole 1,4-dioxane M CH 2Cl 2 CHCl 3 CCl 4 C 6H 14 CH 2Cl 2 CHCl 3 CCl 4 C 6H 14 CH 2Cl 2 CHCl 3 CCl 4 C 6H 14 CH 2Cl 2 CHCl 3 CCl 4 C 6H 14 0001 10491 9651 9052 10559 10516 9664 9046 10568 10528 9658 9004 10552 10522 9652 9070 10490 0002 10508 9666 9076 10533 10520 9672 9066 10576 10512 9660 9016 10548 10498 9656 9084 10496 0003 10524 9653 9064 10547 10510 9678 9048 10580 10504 9664 8996 10556 10502 9632 9054 10512 0004 10497 9655 9052 10539 10520 9664 9060 10548 10506 9650 9036 10556 10506 9641 9040 10524 0005 10495 9652 9065 10560 10526 9660 9072 10540 10509 9672 9054 10576 10552 9640 9066 10528 0006 10494 9649 9060 10536 10524 9674 9056 10576 10520 9651 9030 10568 10500 9650 9070 10530 0007 10486 9648 9054 10512 10518 9662 9082 10558 10516 9658 9044 10536 10492 9634 9054 10534 0008 10484 9660 9048 10524 10512 9660 9056 10569 10504 9662 9064 10544 10510 9668 9040 10540 0009 10476 9664 9049 10544 10506 9678 9076 10590 10508 9664 9064 10544 10516 9633 9052 10544 0010 10472 9676 9061 10548 10501 9678 9016 10630 10520 9656 9044 10552 10510 9638 9054 10560 Table 2 DENSITY (kgm -3 ) VALUES OF IODINE - ETHER SYSTEMS IN DIFFERENT SOLVENTS AT 303 K Conc Diphenylether 4-chloroanisole anisole 1,4-dioxane M CH 2Cl 2 CHCl 3 CCl 4 C 6H 14 CH 2Cl 2 CHCl 3 CCl 4 C 6H 14 CH 2Cl 2 CHCl 3 CCl 4 C 6H 14 CH 2Cl 2 CHCl 3 CCl 4 C 6H 14 0001 12689 14134 15186 6404 12611 14083 15207 6383 12583 14098 15198 6343 12601 14083 15195 6362 0002 12641 14136 15142 6385 12580 14070 15166 6365 12578 14066 15150 6370 12577 14072 15191 6355 0003 12705 14342 15148 6401 12601 14062 15126 6372 12632 14073 15161 6352 12576 14058 15162 6362 0004 12694 14107 15196 6436 12616 14059 15218 6387 12582 14130 15201 6333 12628 14110 15164 6375 0005 12598 14042 15190 6361 12616 14109 15089 6349 12601 14099 15180 6376 12622 14080 15141 6356 0006 12675 14180 15200 6414 12626 14095 15197 6391 12587 14122 15230 6367 12607 14097 15200 6378 0007 12633 14196 15149 6390 12580 14080 15152 6373 12607 14075 15168 6385 12588 14070 15175 6366 0008 12698 14348 15203 6430 12580 14067 15143 6386 12645 14082 15161 6354 12597 14065 15173 6382 0009 12695 14096 15149 6436 12610 14135 15197 6410 12586 14133 15218 6335 12638 14109 15153 6389 0010 12615 14030 15189 6378 12627 14056 15098 6351 12597 14110 15195 6379 12622 14078 15158 6365 Table 3 VISCOSITY (x10-4 Nsm -2 ) VALUES OF IODINE - ETHER SYSTEMS IN DIFFERENT SOLVENTS AT 303 K Conc Diphenylether 4-chloroanisole anisole 1,4-dioxane M CH 2Cl 2 CHCl 3 CCl 4 C 6H 14 CH 2Cl 2 CHCl 3 CCl 4 C 6H 14 CH 2Cl 2 CHCl 3 CCl 4 C 6H 14 CH 2Cl 2 CHCl 3 CCl 4 C 6H 14 0001 563 671 857 339 559 673 870 335 542 658 866 331 557 665 870 334 0002 563 671 863 339 557 663 870 332 543 662 858 329 554 663 880 334 0003 567 690 866 341 564 659 863 333 547 661 868 330 555 662 876 331 0004 566 675 861 340 550 660 870 335 547 669 860 327 563 665 873 334 0005 561 670 855 336 561 662 867 331 548 657 865 329 552 660 868 334 0006 564 683 864 337 556 656 873 337 551 662 873 329 556 660 867 332 0007 563 684 854 339 556 657 870 334 553 668 870 332 561 668 875 334 0008 565 683 867 339 557 666 866 333 552 663 867 329 559 666 876 334 0009 569 676 843 340 553 657 878 334 546 664 878 327 558 665 876 333 0010 560 674 867 335 562 654 872 332 550 659 870 331 555 662 876 331 903

S J Askar Ali et al J Chem Pharm Res, 2012, 4(1):901-912 U (ms -1 ) 1056 1055 1054 1053 1052 1051 1050 1049 1048 1047 1046 0000 0002 0004 0006 0008 0010 0012 Fig1 Plots of Ultrasonic velocity Vs Concentration of iodine and ethers in dichloromethane 9690 9680 9670 U (ms -1 ) 9660 9650 9640 9630 9620 0000 0002 0004 0006 0008 0010 0012 Fig2 Plots of Ultrasonic velocity Vs Concentration of iodine and ethers in chloroform 904

S J Askar Ali et al J Chem Pharm Res, 2012, 4(1):901-912 U (ms -1 ) 9090 9080 9070 9060 9050 9040 9030 9020 9010 9000 8990 0000 0002 0004 0006 0008 0010 0012 Fig3 Plots of Ultrasonic velocity Vs Concentration of iodine and ethers in carbon tetrachloride U (ms -1 ) 10640 10620 10600 10580 10560 10540 10520 10500 10480 0000 0002 0004 0006 0008 0010 0012 Fig4 Plots of Ultrasonic velocity Vs Concentration of iodine and ethers in n-hexane 905

S J Askar Ali et al J Chem Pharm Res, 2012, 4(1):901-912 0724 0722 β (x10-9 kg -1 ms 2 0720 0718 0716 0714 0712 0710 0000 0002 0004 0006 0008 0010 0012 Fig5 Plots of Adibatic compressibility Vs Concentration of iodine and ethers in dichloromethane 0770 0765 β (x10-9 kg -1 ms 2 0760 0755 0750 0745 0000 0002 0004 0006 0008 0010 0012 Fig6 Plots of Adibatic compressibility Vs Concentration of iodine and ethers in chloroform 906

S J Askar Ali et al J Chem Pharm Res, 2012, 4(1):901-912 β (x10-9 kg -1 ms 2 0816 0814 0812 0810 0808 0806 0804 0802 0800 0798 0796 0000 0002 0004 0006 0008 0010 0012 Fig7 Plots of Adibatic compressibility Vs Concentration of iodine and ethers in carbon tetrachloride β (x10-9 kg -1 ms 2 1435 1430 1425 1420 1415 1410 1405 1400 1395 1390 1385 0000 0002 0004 0006 0008 0010 0012 Fig8 Plots of Adibatic compressibility Vs Concentration of iodine and ethers in n-hexane 907

S J Askar Ali et al J Chem Pharm Res, 2012, 4(1):901-912 Table 4 ABSORPTION COEFFICIENT (x10-15 Npm -1 s 2 ) VALUES OF IODINE - ETHER SYSTEMS IN DIFFERENT SOLVENTS AT 303 K Conc Diphenylether 4-chloroanisole anisole 1,4-dioxane M CH 2Cl 2 CHCl 3 CCl 4 C 6H 14 CH 2Cl 2 CHCl 3 CCl 4 C 6H 14 CH 2Cl 2 CHCl 3 CCl 4 C 6H 14 CH 2Cl 2 CHCl 3 CCl 4 C 6H 14 0001 10106 13884 19994 11822 10026 13927 20311 11706 9703 13620 20526 11671 9978 20143 20175 11950 0002 10089 13827 20041 11952 10002 13699 20231 11607 9779 13730 20314 11564 10017 20044 20311 11935 0003 10067 14056 20186 11948 10133 13600 20261 11604 9828 13679 20669 11621 10019 20224 20464 11778 0004 10134 13973 20093 11863 9852 13679 20205 11744 9870 13858 20171 11548 10111 20229 20497 11814 0005 10126 13955 19857 11808 10027 13676 20227 11708 9849 13532 20196 11480 9781 20109 20218 11856 0006 10121 14098 20085 11803 9927 13512 20347 11718 9878 13714 20457 11511 10017 20025 20105 11707 0007 10158 14102 19977 11994 9981 13609 20148 11692 9918 13844 20387 11682 10138 20385 20435 11801 0008 10148 13893 20232 11903 10022 13812 20240 11625 9902 13722 20186 11627 10044 20033 20551 11739 0009 10259 13964 19754 11859 9949 13488 20315 11538 9828 13689 20380 11574 9974 20304 20494 11679 0010 10156 13949 20181 11781 10099 13502 20711 11436 9852 13629 20341 11613 9962 20173 20464 11618 Table 5 INTERNAL PRESSURE (X10 3 atm) VALUES OF IODINE - ETHER SYSTEMS IN DIFFERENT SOLVENTS AT 303 K Conc Diphenylether 4-chloroanisole anisole 1,4-dioxane M CH 2Cl 2 CHCl 3 CCl 4 C 6H 14 CH 2Cl 2 CHCl 3 CCl 4 C 6H 14 CH 2Cl 2 CHCl 3 CCl 4 C 6H 14 CH 2Cl 2 CHCl 3 CCl 4 C 6H 14 0000 4928 4073 3753 2333 0001 4980 4093 3727 2399 4936 4088 3760 2380 4849 4045 3760 2356 4923 4065 3754 2378 0002 4960 4091 3728 2397 4917 4053 3749 2363 4858 4051 3731 2355 4909 4055 3771 2374 0003 4991 4189 3738 2405 4953 4037 3732 2366 4890 4047 3759 2354 4911 4055 3764 2364 0004 4988 4097 3738 2409 4894 4042 3758 2378 4877 4086 3741 2337 4958 4071 3762 2376 0005 4940 4070 3719 2375 4939 4056 3728 2355 4881 4036 3744 2353 4894 4052 3740 2372 0006 4973 4136 3741 2391 4917 4032 3763 2382 4887 4062 3773 2349 4921 4053 3749 2366 0007 4958 4141 3714 2393 4906 4036 3743 2366 4903 4068 3754 2367 4937 4073 3765 2371 0008 4983 4166 3750 2403 4912 4060 3737 2367 4910 4054 3742 2349 4926 4058 3769 2372 0009 5004 4093 3690 2405 4904 4042 3768 2372 4866 4066 3776 2334 4930 4071 3763 2369 0010 4939 4073 3746 2371 4945 4017 3750 2344 4881 4046 3757 2358 4916 4055 3763 2355 Table 6 COHESSIVE ENERGY (kjmol -1 ) VALUES OF IODINE - ETHER SYSTEMS IN DIFFERENT SOLVENTS AT 303 K Conc Diphenylether 4-chloroanisole anisole 1,4-dioxane M CH 2Cl 2 CHCl 3 CCl 4 C 6H 14 CH 2Cl 2 CHCl 3 CCl 4 C 6H 14 CH 2Cl 2 CHCl 3 CCl 4 C 6H 14 CH 2Cl 2 CHCl 3 CCl 4 C 6H 14 0001 33769 35025 38244 32712 33681 35105 38530 32561 33160 34700 38549 32429 33614 34908 38497 32639 0002 33773 35006 38371 32792 33638 34840 38520 32431 33236 34834 38381 32290 33592 34852 38684 32630 0003 33814 35333 38462 32843 33835 34730 38455 32443 33316 34786 38633 32377 33607 34890 38689 32468 0004 33834 35137 38342 32728 33399 34779 38492 32550 33371 34985 38351 32258 33796 34899 38661 32565 0005 33771 35076 38168 32651 33712 34781 38509 32442 33351 34636 38442 32258 33382 34814 38498 32617 0006 33793 35301 38369 32612 33542 34615 38600 32601 33430 34802 38608 32269 33609 34781 38432 32435 0007 33808 35309 38218 32779 33592 34690 38502 32492 33493 34972 38575 32422 33776 35027 38667 32566 0008 33812 35152 38458 32724 33641 34934 38475 32441 33443 34834 38467 32342 33680 34912 38715 32511 0009 33969 35151 37982 32728 33512 34614 38654 32402 33303 34821 38674 32252 33599 34919 38704 32445 0010 33748 35148 38458 32580 33752 34598 38728 32329 33386 34705 38543 32366 33552 34858 38687 32387 Table 7 STABILITY CONSTANT (dm -3 mol -1 ), FREE ENERGY (kjmol -1 ), FREE ENERGY OF ACTIVATION (kjmol -1 ) AND RELAXATION TIME (x10-13 s) VALUES OF CERTAIN CHARGE TRANSFER COMPLEXES OF IODINE - ETHER SYSTEMS AT 303 K DONOR K G G # τ CH 2Cl 2 CHCl 3 CCl 4 C 6H 14 CH 2Cl 2 CHCl 3 CCl 4 C 6H 14 CH 2Cl 2 CHCl 3 CCl 4 C 6H 14 CH 2Cl 2 CHCl 3 CCl 4 C 6H 14 DIPHENYL ETHER 742 512 504 373-107 -95-97 -90 34 40 49 38 54 68 92 63 4-CHLORO ANISOLE 589 434 364 346-101 -92-90 -89 34 40 49 38 53 67 93 62 ANISOLE 533 376 355 312-97 -90-88 -86 33 40 49 38 52 67 93 62 1,4-DIOXANE 403 315 335 240-92 -83-88 -80 34 40 49 38 53 68 94 63 Correlation of stability constant with molecular properties The complex formation is also influenced by the molecular properties such as polarizability (α), dipole moment (µ) and dielectric constant (ε) of donor molecules [21-23] These parameters for the four ethers are listed in Table 8 908

S J Askar Ali et al J Chem Pharm Res, 2012, 4(1):901-912 Plots of log K against polarizability of the donor in different solvents are given in Fig9 These plots show that formation constant (K) increases with increase in polarizability of donor molecules Thus, polarizability of donor molecules plays significant role during complexation Table 8 POLARIZABILITY, DIPOLE MOMENT AND DIELECTRIC STRENGTH FOR ETHERS AND SOLVENTS α µ ε α µ ε CH 2Cl 2 680 160 908 Diphenylether 2086 103 268 CHCl 3 850 101 481 4-chloroanisole 1475 162 784 CCl 4 1050 000 224 Anisole 1307 108 430 C 6H 14 1160 008 189 n-hexane 1000 000 222 log K 20 19 18 17 16 15 14 13 8 10 12 14 16 18 20 22 Polarizability (α) /10-30 m 3 dichloromethane with 1,4dioxane, anisole, 4chloroanisole, diphenyl ether chloroform with 1,4dioxane, anisole, 4chloroanisole, diphenyl ether" carbon tetrachloride with 1,4dioxane, anisole, 4chloroanisole, diphenyl ether" n-hexane with 1,4dioxane, anisole, 4chloroanisole, diphenyl ether" Fig9 Plots of log K Vs Polarizability of ethers The plots of log K against dipole moment of the donor are given in Fig10 From these plots it is clear that stability constant K increase with dipole moment in three systems But in the case of diphenyl ether, the stability constant is abnormally high even with different ethers having low dipole moment This may be due to high π electron density in diphenyl ether Plots of log K against dielectric constant of the donor are given in Fig11 These plots also show that the stability constant value increases with increase in dielectric constant of donor molecules except diphenyl ether 909

S J Askar Ali et al J Chem Pharm Res, 2012, 4(1):901-912 log K 20 19 18 17 16 15 14 13 12 0 05 1 15 2 Dipole Moment (m) D dichloromethane with 1,4dioxane, anisole, 4chloroanisole, diphenyl ether chloroform with 1,4dioxane, anisole, 4chloroanisole, diphenyl ether carbon tetrachloride with 1,4dioxane, anisole, 4chloroanisole, diphenyl ether n-hexane with 1,4dioxane, anisole, 4chloroanisole, diphenyl ether Fig10 Plots of log K Vs Dipole Moment of ethers log K 20 19 18 17 16 15 14 13 12 0 2 4 6 8 10 Dielectric Strength (ε) dichloromethane with 1,4dioxane, anisole, 4chloroanisole, diphenyl ether chloroform with 1,4dioxane, anisole, 4chloroanisole, diphenyl ether carbon tetrachloride with 1,4dioxane, anisole, 4chloroanisole, diphenyl ether n-hexane with 1,4dioxane, anisole, 4chloroanisole, diphenyl ether Fig11 Plots of log K Vs Dielectric Strength of ethers These correlations of K with molecular properties indicate that it is the polarizability factor which mainly determines the ease of complexation Thus, the acceptor molecule first polarizes the donor molecule during the formation of a charge transfer complex The stability of charge transfer complex is also influenced by the polarity of the medium (Table 8) The plots of log K Vs dielectric strength of the solvents are presented in Fig12 As the dielectric constant of the medium increases, the stability constant of the charge transfer complex also increases This can be explained as follows The charge transfer complex is more polar than the donor and acceptor molecules and hence it is more soluted Therefore, high dielectric constant of the medium favours the formation of such a complex 910

S J Askar Ali et al J Chem Pharm Res, 2012, 4(1):901-912 log K 90 80 70 60 50 40 30 20 10 000 200 400 600 800 1000 Dielectric Strength (ε) diphenyl ether in n-hexane, carbon tetrachloride, chloroform, dichloromethane 4-chloroanisole in n-hexane, carbon tetrachloride, chloroform, dichloromethane anisole in n-hexane, carbon tetrachloride, chloroform, dichloromethane 1,4-dioxane in n-hexane, carbon tetrachloride, chloroform, dichloromethane Fig12 Plot of log K Vs Dielectric strength of solvents CONCLUSION Iodine forms thermodynamically stable charge transfer complexes with ethers The formation constants correlate with the molecular properties of donor molecules and the correlation is better with polarizability The stability of such complexes is also influenced by the dielectric constant of the medium Acknowledgement The authors thank the Principal and the Management of The New College, Chennai 600 014, for their constant support and encouragement REFERENCES [1] V Kannappan, R Jaya Santhi, Indian J Pure and Applied Physics, 2005, 43, 750 [2] SJ Askar Ali; K Rajathi and A Rajendran, J Chem Pharm Res, 2011, 3(5), 348-358 [3] VD Bhandarkkar; OP Chimankar and NR Pawar, J Chem Pharm Res, 2010, 2(4), 873-877 [4] SR Aswale, SS Aswale, AB Dhote and DT Tayade, J Chem Pharm Res, 2011, 3(6), 233-237 [5] OP Chimankar, R Shiriwas and VA Tabhane, J Chem Pharm Res, 2011, 3(3), 587-596 [6] S Jayakumar, N Karunanithi, V Kannappan, S Gunasekaran, Asian Chem Letters, 1999, 3, 224 [7] MS Neuman, Blum, J Am Soc, 1964, 86, 5600 [8] Rose Venis and Rosario Rajkumar, J Chem Pharm Res, 2011, 3(2), 878-885 [9] S Thirumaran and S Sudha, J Chem Pharm Res, 2010, 2(1), 327-337 [10] OP Chimankar, R Shiriwas and VA Tabhane, J Chem Pharm Res, 2011, 3(3), 579-586 [11] OP Chimankar, R Shiriwas and VA Tabhane, J Chem Pharm Res, 2011, 3(3), 587-596 [12] V Kannappan, R Jaya Santhi, S Xavier Jesu Raja, Phys Chem Liq, 2003,14(2), 133 [13] V Kannappan, S Kothai, J Acous Soc India, 2002, 30, 76 [14] GP Pethe, AA Ranteka, TR Lawankar and ML Narwade, J Chem Pharm Res, 2010, 2(4), 68-74 [15] V Kannappan, S Kothai, Indian J Pure and Applied Physics, 2002, 40, 17 [16] V Kannappan, R Jaya Santhi R, EJP Malar, Phys Chem Liq, 2002, 40, 507 [17] VA Tabhane, Sangeeta Agarwal, KG Revetkar, J Acous Soc Ind, 2000, 8, 369 [18] Anwar Ali, Anil Kumar Nain, Acoustics Letters, 1996, 19, 181 [19] SC Bhatt, Harikrishnan Semwal, Vijendra Lingwal, J Acous Soc Ind, 2000, 28, 275 [20] PS Nikam, Hiray, Indian J Pure and Applied Physics, 1991, 29, 601 [21] Timmerniam, J Physico-chemical constants of pure organic compounds, Elsevier, 1950 [22] S Kothai, Ph D Thesis, University of Madras, 2003 911

S J Askar Ali et al J Chem Pharm Res, 2012, 4(1):901-912 [23] AL McClellan, Tables of experimental dipole moments, WH Freeman & Company, San Francisco and London, 1963 912