## volume of activation, $$\Delta ^{\ddagger}V$$

https://doi.org/10.1351/goldbook.V06644
A quantity derived from the pressure dependence of the @O04322@ of a reaction (mainly used for reactions in solution), defined by the equation: $\Delta ^{\ddagger }V=- R\ T\ (\frac{\partial (\ln k)}{\partial p})_{T}$ providing that the rate constants of all reactions (except first-order reactions) are expressed in pressure-independent concentration units, such as $$\text{mol dm}^{-3}$$ at a fixed temperature and pressure. The volume of @A00093@ is interpreted, according to @T06470@, as the difference between the partial molar volumes of the @T06468@ ($$V$$) and the sums of the partial volumes of the reactants at the same temperature and pressure, i.e. $\Delta ^{\ddagger}V = ^{\ddagger}V- \sum \left(r\ V_{\text{R}}\right)$ where $$r$$ is the order in the reactant R and $$V_{\text{R}}$$ its partial molar volume.
Source:
PAC, 1994, 66, 1077. (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)) on page 1175 [Terms] [Paper]