Activation Volume change

There is one important caveat to consider before one starts to interpret activation volumes in temis of changes of structure and solvation during the reaction the pressure dependence of the rate coefficient may also be caused by transport or dynamic effects, as solvent viscosity, diffiision coefficients and relaxation times may also change with pressure [2]. Examples will be given in subsequent sections. 

If, in analogy to equation (A3.6.5). one denotes the change of activation volume with respect to some... 

High pressure can influence reactions characterized by negative molar and activation volumes in the following aspects (i) acceleration of the reaction, (ii) modification of regioselectivity and diastereoselectivity, and (iii) changes in chemical equilibria. The pressure dependence on the rate constant of the reaction is expressed as follows ... 

Kaiser, W.M. (1982). Correlation between changes in photosynthetic activity and changes in total protoplast volume in leaf tissue from hygro-, meso-, and xer-ophytes under osmotic stress. Planta, 154, 538-45. 

Due to the AV (volume change of activation) of Claisen rearrangements having a negative value, as in the Diels-Alder reactions, the Claisen rearrangement reaction is expected to be accelerated by water according to the same effect.151,152... 

A discussion of the cardiac cycle requires the correlation of pressure changes ventricular volume changes valve activity and heart sounds. In this section, the focus will be on the left side of the heart (see Table 13.3). Identical events occur simultaneously on the right side of the heart however, the pressures are lower. 

Activation volumes may be used to elucidate the mechanisms of classes of reactions involving the same functional groups, and changes in activation volumes can be used to characterize the point at which a change in reaction mechanism takes place in a series of homologous reactions. 

If A and B are miscible liquids, increasing the pressure will change the rate constant k according to Equation 3. The rate may increase or decrease, depending on the sign of the activation volume 4 V. ... 

In active material of both electrodes of the EC with purely double electric layer , volume changes do not take place during charge-discharge processes. That s why it is not expedient to add binder into active material. 

The character of carbonaceous material s influence on performance of asymmetric EC systems (carbon - NiOx) is more complicated than that of carbon-carbon system. It is determined by the higher operating potential of NiOx electrode, due to which oxidation and volume changes in electrode active mass upon charge-discharge processes are taking place as the reaction of transformation of Ni(OH)2 into NiOOH is occurring. 

When a chemical reaction takes place, the volume change accompanying the formation of the transition state is known as the volume of activation, AV. It can be expressed as... 

Negative volumes of activation for the forward (—23.6 cm3 mol-1) and reverse (—12.6 cm3 mol-1) reactions were observed for the formation of the initial complex between 29 and a-CD. The overall volume change for this complex formation was... 

---