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Initial State and Transition State Solvation for the Solvolysis of ^Razis

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Initial State and Transition State Solvation for the Solvolysis of ^Razis 宙시 State and Transition State Solvation for the Solvolysis of trans-[Co(N-ete^2ClJ^ Bull. Korean Chem. Soc.f Vol. 11, No. 4, 1990 309 aqueous HC1 solution. The reaction product was extracted 2, (a) H. Kotsuki, Y. Ushio, I. Kadota, and M. O산 ii,/ ()rg. three times with ether (20 ml x 3) and the organic옹 were Chem., 54, 5153 (1989); (b) H. Kots니 d, Y. Ushio, I. separated and dried over anhydrous magnesium sulfate. The Kadota, and M. Ochi, Chem. Lett., 927 (1988); (c) B. P. ether was removed by rotatory evaporator. The GLC ana­ M니 ndy and M. Bjorklund. Tetrahedron Lett., 26, 3899 lysis indicated an exo/endo ratio of 83:17 (quantitative yield). (1985); (d) H. A. Bates and P.-N. Deng, / ()rg. Chem., General procedure for endo-5,7-dimethyl-6,8-dioxabicy- 48, 4479 (1983). clo[3.2.1]octane (5). To a dried ZnCl2(2 eq.) was added drop­ 3, (a) B. P. Mundy and W. G. Bommann,/ ()rg. Chem., 49, wise 0.2 g (1.4 mmol) of methyl vinyl keton dimer (1) in 2 ml 5264 (1984); (b) T. Cohen and M. Bhupathy, Tetrahed- ) of CH2C12 and 3 eq. of Zn(BH4 2 (0.8M solution in THF) res­ ron Lett., 24, 4163 (1983); (c) P. Chaquin, J-P. Morizur, pectively at 0°C. After 2 hrs stirring at 0°C, 10 mZ of 15% and J. KossanyiJ. Am. Chem. Sog, 99,903(1977); (d) K. aqueous HC1 solution was added to this reaction mixture and Mori, Tetrahedron, 30, 4223 (1974). worked-up as above. The GLC analysis indicated an exo/ 4, B. P. Mundy, R. D. Otzenberger, and A. R. Debemar- endo ratio of 19:81 (quantitative yield). dis, J. (”g. Chem.f 36, 2390 (1971). See Also 1(c), 2(c) 1H-NMR(CDCl3)of(4):^(ppm)4.20(lH,m),3.99(lH,br and 3(a). s), 1-70 (6H, br s), 1.42 (3H, s), 1.19 (3H, d, J= 10 Hz). 5・(a) M. Bjorklund, J.-G. Jun, and B. P. Mundy, Tetrahed­ 1H-NMR (CDC1J of (5): & (ppm) 4.18 (2H, m), 1.70 (6H, ron Lett., 26, 3895 (1985); (b) B. P. Mundy, K. B. Lip- br s), 1.42 (3H, s), 1.31 (3H, partially buried doublet). kowitz, and G. W. Dirks, Synth. 5, 7 (1975). IR(neat) of (4): 2935,1460,1443, 1380, 1237, 1185, 1099, 6. K. B. Lipkowitz, B. P. Mundy, and D. Geeseman, Synth. 1011, 976, 839 cm-1. Commnn.f & 453 (1973). ' IR (neat) of (5): 2934, 1464, 1442,1379,1259, 1190,1097, 7. K. B. Lipkowitz, S. Scarpone, B. P. Mundy, and W. G. 1020, 837 cm-1. Bornmann, J. ()rg. Chem., 44, 486 (1979). Acknowledgement. The present studies were support­ 8. B. P. Mundy and T. R. Schwartz, J. ()rg. Chem., 47,576 ed by the Basic Science Research Institute Program, Minis­ (1982). try of Education, 1989. 9. D. J. Cram and K. R. Kopecky, J. Am. Chem. Soc., 81, 2748 (1959). References 10. J. W. Comforth, and R. H. Cornforth and K. K. Mathew, / Chem. Soc.t 112, (1959). 1- (a) Y. Noda and M. Kikiurhi, Chem. Lott., 1755 (1989); 11. M. Cherest, H. Felkin, and N. Prudent, Tetrahedron (b) V. Sinn well, S. Schulz, W. Francke, R. Kittmann, Utt., 2199 (1968). and D. Schneider, Tetrahedron Lett., 26,1707(1985); (c) 12. T. Nakata, T. Tanaka, and T. Oishi, Tetrahedron Lett., B. P. Mundy, K. B. Lipkowitz, and G. W. Dirks, Hetero­ 22, 4723 (1981). cycles, 6, 51 (1977). 13. P. A. Bartlett, Tetrahedron, 36, 2 (1980). Initial State and Transition State Solvation for the Solvolysis of ^razis—[Co(N—eten)2Cl2]+ in Binary Aqueous Mixtures: Excess Free Energy, Free Energy Cycle and Reaction Mechanism Yu Chui Park* and Young Je Cho Department of Chemistry, Kyungpook National University, Taegu 702 - 701 Received March 9, 1990 The rates of solvolysis of /r(7M5-[Co(N-eten)2C12)+ (N-eten; N-ethylethylenediamine) have been investigated using spectro­ photometric method in binary aqueous mixtures containing methyl alcohol, isopropyl alcohol, /-butyl alcohol, ethylene glycol and glycerol. The values of 厶4S*obtained from temperature effect on the rate constants were 80~84 kjmol'1 and -2845 JK-^ob1. Extrema found in the variation of the enthalpy and entropy of activation with solvent composition cor- r은 lated very well with extrema in the variation of 하 】e physical properties of mixture which relate to sharp change in the sol- vent struct나 je The reaction mechanism was discussed in terms of correlation diagrams involving the exess molar Gibbs function of mixing for the binary mixtures. The behavior of this cobalt(III) complex was compared with that of『butyl chloride. The application of free energy cycle to the process initial state to transition state in water and in the mixture showed that the solvation of transition state had dominant effect on the rates in the mixtures. It was found that SNl character was in­ creased with increasing the content of co-solvent in the mixture. Introduction (Ill)-ammine complexes in mixed solvents.1-10 The solvent effects on initial state and transition state in organic and in- There have been numerous studies of solvalysis of cobalt organic reactions were published and reviewed.11'16 It has 310 BitlL Korean Chem. Soc., Vol. 11, No. 4, 1990 Yu Chui Park and Young Je Cho long been recognized that solvolysis reactions of the cobalt Table 1. Rate Constants and Activation Parameters for Solvolysis (Hl) complex have bond breaking dissociation mechanism in­ of ZwM.s-[Co(N-eten)2 CI2]+ in Water- Isopropyl Alcohol volving the rate determining loss of a leaving group.17'21 Recently, free energy cycle5^10 and excess free energy /-PrOH k x 1()4, sec'1 사广 AS* ((iE)22'23 have been used in the diagnosis of reaction mecha­ w/w % 25 °C 30 °C 35 °C 40 °C kjmol-1 JK-knoL nism. The followings are application of free energy cycle 0 2.65 4.32 7.45 14.31 84 -28 【elating the process initial state to transition state for the 5 2.37 3.90 6.84 12.55 84 -32 ^r(7ns-[Co(N-eten)2CI2]+ to give ^r(7M.s-[Co(N-eten)2Cl]2 + 8 2.31 3.50 6.01 11.04 83 -38 together with the chloride in the transition state in water(w) 10 3.04 3.31 5.70 10.12 80 -46 and in the mixed solvent(s). 20 1.99 3.15 5.69 10.10 82 -40 initial fft&te transition state 25 1.98 3.09 5.39 9.82 81 -44 + " 30 1.95 3.07 5.21 ICO*미 」g ------------- > ICoL.CI+ Cl；w> 9.64 80 -45 44 1.65 2.92 5.09 8.52 82 -KcCoL^Clt) 4G；(CoLaClf -41 + AG； . )(s)-------------- > 【飢 丄미 J⑸ + Cl；s) Table 2. Rate Constants for Solvolysis of /mM5-[Co(N-eten)2C12]+ L ■ N-«thylethyleoediMine in Binary Mixtures at 25 °C Equation (1) results from this cycle, where 厶(” is the free MeOH rates Z-BuOHrt rates Glycol rates Glycerol rates energy of transfer for species i between water and the mix­ w/w% /ex 104 w/w% Z'X 1()4 w/w% /?xl04 w/w% /cxlO4 ture. 10.0 2.42 5.0 2.55 7.5 2.63 4.9 2.61 厶G；=zlG$+厶G? {CoL2Cl2+)+AGl (CT) 16.0 2.14 10.0 2.50 10.0 2.60 8.2 2.57 20.0 2.01 15.0 2.50 14.5 2.47 10.0 2.54 - △GMGLCl；) (1) 22.2 1.62 20.0 2.45 19.3 2.43 16.2 2.50 Converting of free energies of activation, △(；*, into first 28.4 1.56 25.0 2.31 26.6 2.32 20.0 2.36 order rate constants, equation ⑴ can be rearranged to equa­ 34.7 1.49 30.0 2.10 30.0 1.94 24.() 2.10 tion (2) 40.0 1.38 35.0 1.94 35.8 1.92 30.0 2.07 50.0 1.28 40.0 1.38 49.3 1.72 40.0 2.06 2,303kTlog (切 W々s) -厶G?(C「)=4G?(C汉々C『+) 아 *tes constant and activation parameter were listed in ref. 28. -AG?(CoLtCU) (2) Values for k can be determined experimentally and values for perat니 re was maintained by Haake F 4391 circulator. 厶 ； 「) G (C are available24 for mixture of water with a range of All kinetic experiments were performed in the presence co-solvents enabling the left hand side of equation (2) to be of 0.01 M aqueous hydrochloric acid (pH 2), 0.5 M of ionic calculated. Therefore a positive value of left-hand side of strength (adjusted with NaCl) and binary aqueous mixtures. equation (2) means that the effect of solvent structure on the In this acidic condition the side reaction to form hydroxo ion in the initial state dominates over that on the ion in the complex, -[Co(N-eten)2OHCl]+ was repressed and ne­ transition state and negative value indicates the opposite.25 gligible.27 Rate constants were calculated from gradient of We here report the results of kin은 tic investigation of the plots of log(/l厂)!(ArA °。) against time t and at equilib­ sovolysis of -[Co(N-eten)2Cl2]+ in binary aqueous mix­ rium. where Ao, At and indicate the absorbance of com­ tures. The mechanism of solvolysis is represented by appli­ plex at time, f 그 。, t = t and t = " respectiv이 y.
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