If you measure rate constants by randomly selecting the last four digits of chemistry professors’ phone numbers, this effect causes the pre-exponential factor and activation energy to appear to be proportional. For 10 points each:
[10h] Name this controversial effect, potentially just a mathematical artifact, which causes the isokinetic temperature to seem to be constant.
ANSWER: entropy-enthalpy compensation [or enthalpy-entropy compensation; or EEC; or S-H compensation or H-S compensation; prompt on compensation; prompt on Meyer-Neldel rule] (The lead-in is a notorious homework problem in Chapter 7 of Chemical Kinetics: The Study of Reaction Rates.)
[10m] For instance, the enthalpic barrier to this process, the diffusion of adsorbed atoms across a surface, is compensated by the attempt frequency. Water conducts protons via this generically named process in the Grotthuss mechanism.
ANSWER: surface hopping [or hopping conduction; accept jumping; prompt on quantum tunneling]
[10e] As another example, the enthalpic benefit of protein-ligand binding is compensated by the loss of degrees of freedom for this process. This process occurs at single bonds to interconvert molecular conformers.
ANSWER: rotation [or rotate or rotating]
<AS, Chemistry>