Activation and Reaction Volumes in Solution. 3

High-sensitivity sapphire cells for high pressure NMR spectroscopy on proteins

“…In a recent study we could not find a significant pressure dependence of the cis-trans-equilibrium using a glass-cell [16] at the actual experimental error. This result was in line to previous reports [17][18][19] which have stated that conformational equilibria in small molecules are affected by pressure only if it changes local electrical charges of the concerned conformational states. Examples are N-acetyl-L L -proline-NH-methylamide and glycylsarcosine [20].…”

The Effect of Pressure on Organic Reactions in Fluids—a New Theoretical Perspective

“…[1][2][3][4]10] (1) Volumes of activation vary with pressure and usually maximize in magnitude as the pressure approaches zero. Figure 2s hows typical ln k vs.p ressure relations for reactions with positive,z ero and negative activation volumes.T he curves for D°V < 0a nd D°V > 0u sually become flat as pressure increases;t he slope is maximal (in magnitude) at zero pressure.The convention has been to use the D°V value at zero pressure or 1atm, such as those in Table 1 Roald Hoffmann is entering the last year of his organized research career.Organic reactions, of just the kind discussed in this paper, have been on his mind for over half acentury.B ut the effect of high pressure on such reactions (which he should have known about, but didn't) entered his consciousness only recently,asaresult of ap roductive collaboration with Neil Ashcroft on the effect of extreme pressure on the electronic structure of all forms of matter.A nd, more specifically,int hinking about the remarkable ordered polymerization of benzene under compressiondiscovered by John Badding and Vincent Crespi and their collaborators.…”

Reaction volume in aqueous solutions in problem solving

“…The volume of water dissociation has the same value but opposite sign to the volume of reaction (12), that is, it equals about -19 cm 3 /mole (in the presence of dilute 1-1 electrolyte). According to the Le Chatelier's principle the negative value of volume of reaction implies that the water dissociation reaction shifts to the right at elevated pressures.…”

“…The fact that the volume of the products of reaction in solution is not equal to the sum of volumes of reactants is well-known, and numerous studies of reaction volumes in solution have been reported in the scientific literature [1][2][3]. However, the volume of chemical reaction in solution is ignored in classroom teaching.…”