Multidimensional PE Surfaces

Question 1

number of surfaces

Answer 1

3N-6 position coords and one coord for energy

Question 2

co-linear PES

Answer 2

bottom of product valley lies well below reactants, no symmetry about diagonal

Question 3

what does an early barrier mean

Answer 3

energy needed to force A to B therefore translational promotes reaction

Question 4

what does a late barrier mean

Answer 4

energy used to break BC bond meaning translational energy isn’t effective at promoting reaction

Question 5

where’s energy released in early barrier reactions

Answer 5

A accelerated towards B giving vibrationally excited AB product

Question 6

where’s energy released in late barrier reactions

Answer 6

C accelerated away from B giving AB…C relative translation

Question 7

increase in exothermicity of reactions and PES

Answer 7

barrier height decreases, earlier barrier and energy released more attractive

Question 8

hammond’s postulate for exo reactions

Answer 8

TS resembles reactants, energetically downhill

Question 9

hammond’s postulate for endo reactions

Answer 9

TS resembles products

Question 10

sources of PES

Answer 10

semi-empirical and ab-initio