Effects on Equilibria

J. Hine, Structural Effects on Equilibria in Organic Chemistyff ohxi Wiley Sons, Inc., New York, 1975, p. 259, and references cited therein. 

Mine, J. "Structural Effects on Equilibria in Organic Chemistry", Wiley-Interscience New York, N.Y., 1975, p. 287. 

In these examples B is a base. The first example is called a secondary isotope effect of the first kind, the next one is a secondary isotope effect of the second kind. The distinction between these is that in the first kind bonds to the isotopic atom have undergone spatial (i.e., structural) change. Halevi has reviewed secondary isotope effects on equilibria and rates. 

All the applications in this chapter will be to the gas phase, in particular to ideal gases. In later chapters the discussion will treat isotope effects on equilibria for condensed phase systems. 

Isotope effects on equilibria have been formulated earlier in this chapter in terms of ratios of (s2/si)f values, referred to as reduced isotopic partition function ratios. From Equation 4.80, we recognize that the true value of the isotope effect is found by multiplying the ratio of reduced isotopic partition function ratios by ratios of s2/si values. Using Equation 4.116 one now knows how to calculate s2/si from ratios of factorials. Note well that symmetry numbers only enter when a molecule contains two or more identical atoms. Also note that at high temperature (s2/si)f approaches unity so that the high temperature equilibrium constant is the symmetry number factor. 

HARTSHORN, s. R. Aliphatic Nucleophilic Substitution (CUP, 1973). HiNE, j. Structural Effects on Equilibria in Organic Chemistry (Wiley, 1975). 

Bone, R. Cullis, R Wolfenden, R. Solvent effects on equilibria of addition of nncleophiles to acetaldehyde and the hydrophilic character of diols.. J. Am. Chem. Soc. 1983,105, 1339-1343. 

Below, solvent effects on activity and stability of enzymes will be discussed, while solvent effects on enzyme selectivity is a large topic which is treated in a separate chapter. Solvent effects on equilibria are treated in Section 1.4. 

Pressure effects on equilibria in liquids or solids are generally less spectacular than temperature effects, at least at the pressures normally encountered in chemical engineering (a few tens of megapascals) or in the environment (hydrostatic pressures in the ocean trenches exceed 100 MPa, but about 40 MPa would be more typical of the ocean floors). Higher lithostatic pressures are, of course, found beneath the Earth s surface, reaching 370 GPa (0.37... 

Equation (35) is an example of a multiparametric equation17 18 64 for describing solvent effects on equilibria and is similar to the multiparametric equations used to describe solvent effects on rates. The use of these equations in describing solvent effects on equilibria involving coordination compounds is, like their application to reaction rates of coordination compounds, not common. Equilibrium (36), where L, U and X are the same as in reaction (12),... 

It is frequently also necessary to assess isotope effects on equilibria. For an equilibrium... 

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