Horrocks L7 Flashcards
(10 cards)
What is the kinetic salt effect
Solvent polarity effects on the rates of ionic reactions
How do we adapt the Kec equation for reactions between ions
previously we ignored activity coefficients but in the reaction between ions we cannot ignore activity coefficients
Kec = γAB[AB]/γA[A]γB[B]
How do we determine the charge on the encounter complex
the charge on the encounter complex is just the sum of than on the surface
ZAB = ZA + ZB
How we estimate how big the factor
γAB/γAγB
log10 γAγB = −0.51√I [za^2+ zb^2
− (zA + zB )^2]
What is the kinetic isotope effects
The kinetic isotope effect (KIE) refers to the change in the rate of a chemical reaction when one of the atoms in the reactants is replaced by one of its isotopes
What does changing 1H for 2D affect
affects the reduced mass µ but not the force constant k. The vibration frequency changes by 1/√2. The zero point energy also changes
What is the primary isotope effect
The primary isotope effect refers to the change in the rate of a chemical reaction when a hydrogen atom (¹H) is replaced by its isotope deuterium when the isotope substitution is directly involved in the rate-determining step of the reaction.
What is the secondary isotope effect
In the secondary isotope effect, the bond containing the isotope is
adjacent to the bond involved in the rate-limiting step. The zero point energy of the transition state now depends on the isotope because it may lie in a functional group whose frequency is large
Describe how the substitution of deuterium (D) for hydrogen (H) affects the tunneling probability
Substituting deuterium (D) for hydrogen (H) increases the mass
m which increases α and causes the tunneling probability to decrease.
This effect is amplified because of the exponential dependence of the tunneling probability. Protons have a much higher probability of tunneling compared to deuterons.
