volume of activation, Δ ‡V

A quantity derived from the pressure dependence of the rate constant of a reaction (mainly used for reactions in solution), defined by the equation:

$Δ ‡ V = − R T ( ∂ ( ln k ) ∂ p ) T$

providing that the rate constants of all reactions (except first-order reactions) are expressed in pressure-independent concentration units, such as $mol dm −3$ at a fixed temperature and pressure. The volume of activation is interpreted, according to transition state theory, as the difference between the partial molar volumes of the transition state ( $V$ ) and the sums of the partial volumes of the reactants at the same temperature and pressure, i.e.

$Δ ‡ V = ‡ V − ∑ r V R$

where $r$ is the order in the reactant R and $V R$ its partial molar volume.

Source:

PAC, 1994, 66, 1077 (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)) on page 1175