Mh. Abraham et al., HYDROGEN-BONDING .34. THE FACTORS THAT INFLUENCE THE SOLUBILITY OF GASES AND VAPORS IN WATER AT 298-K, AND A NEW METHOD FOR ITS DETERMINATION, Perkin transactions. 2, (8), 1994, pp. 1777-1791
The solubility of 408 gaseous compounds in water at 298 K has been cor
related through eqn. (i), where the solubility is expressed as the Ost
wald solubility coefficient, L(w), and the solute explanatory variable
s are R2 an excess molar refraction, pi2H the dipolarity/polarizabilit
y, SIGMAalpha2H and SIGMAbeta2H the effective hydrogen-bond acidity an
d basicity, and V(x) the McGowan characteristic volume. A similar equa
tion using the log L16 parameter instead of V(x) can also be used; L16
is the Ostwald solubility coefficient on hexadecane at 298 K. log L(w
) = -0.994 + 0.577R2 + 2.549 pi2H + 3.813SIGMAalpha2H + 4.841SIGMAbeta
2H - 0.869 V(x) (i) n = 408 rho = 0.9976 sd = 0.151 F = 16810 The main
factors leading to increased solubility are solute pi2H, SIGMAalpha2H
and SIGMAbeta2H values; conversely, the corresponding properties of w
ater are dipolarity/polarizability, hydrogen-bond basicity and hydroge
n-bond acidity. Solute size plays a minor role, and slightly decreases
solubility, contrary to observations on all non-aqueous solvents. It
is shown that this peculiar behaviour of water is due to (a) a greater
increase in the unfavourable cavity effect with increase in solute si
ze, for solvent water, and (b) a smaller increase in the favourable ge
neral dispersion interaction with size, for solvent water. A new metho
d for the determination of log L(w) values is put forward, using the r
elationship L(w) = L16/P where L16 is as above, and P is either the wa
ter-hexadecane partition coefficient or the water-alkane partition coe
fficient. For 14 solutes using the former P-value, agreement with valu
es calculated through eqn. (i) is 0.08 log units on average and for 45
solutes using the latter P-value, the corresponding agreement is 0.15
log units, with log L(w) values ranging up to 8 log units.