Eyring plot curvature

The strong curvature of the Eyring plots at temperatures below 35°C (see ref. 19a, Table V and Figure 6) points to hydrogen-bonded interactions between catalyst molecules, as already observed in 1969 by Uskokovic (52) in the H nuclear magnetic resonance (NMR) spectrum of dihydroquinine. 

The Eyring plot for the monophasic [Fe(CN)g] oxidation of spinach plasto-cyanin in 50 50 (v/v) MeOH-HjO mixed solvent over the extended temperature range 25 to —35 °C, pH 7.0, 1 = 0.10 M(NaCl), exhibits a marked downward curvature. Fig. 6 [105]. The rate constant at 25 °C of 1.04xl0 M" s compares with the value in Table 4 of 8.0 x 10 s . A plot of first-order... 

Fig. 2.12 Examples of non-linear Arrhenius (or Eyring) plots (a) 1u(A oh)7 " ) vs T for the base hydrolysis of trans-Co(en)2ClJ. Curvature may result when k, k2 and A// , not equalling A// in the conjugate-base mechanism (Sec. 4.3.4). Reprinted with permission from C. Blakeley and M. L. Tobe, J. Chem. Soc. Dalton Trans. 1775 (1987). (b) nk vs T for iron removal from C- and N-terminal monoferric transferrin (lower and upper scales respectively). Transferrin contains two iron binding sites = 35 A apart. Either of the two sites, designated C- and N-terminal, can be exclusively labelled by Fe(lll) ions and these may be removed by a strong ligand such as a catechol (see Sec. 4.11). Reprinted with permission from S. A. Kretschmar and K. N. Raymond, J. Amer. Chem. Soc. 108, 6212 (1986). (1986) American Chemical Society.

RNH=Co(cyclam)Cl], then kon=kikJ(k-i+k. The trans-RSSR isomer was shown previously to be the first case, where and k are comparable in magnitude, and curvature in the Eyring plots below 20 °C confirms this behaviour. The results of studies of H/D exchange which are now underway should help to establish a firm mechanistic picture. 

Curvature in an Eyring Plot is Used as Evidence for an Enzyme Conformational Change in the Catalysis of the Cleavage of the Co-C Bond of Vitamin... 

Curvature in an Eyring Plot is Used as Evidence for an Enzyme Conformational Change in the Catalysis of the Cleavage of the Co-C Bond of Vitamin B,2 371 Where TST May be Insufficient 374 The Transi tion States for S, 1 Reactions 377 Comparing Reactivity to Selectivity in Free Radical Halogenation 378... 

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