Vibration and Rotation with Reactivity

Question 1

which energy helps early barrier reactions

Answer 1

translational

Question 2

which energy helps late barrier reactions

Answer 2

vibrational

Question 3

what motion is effective for promoting a reaction

Answer 3

motion along the reaction coordinate

Question 4

why do experimental methods for measuring rotational energy need to be more sensitive

Answer 4

energy difference between rotational levels is only few 10 cm-1 compared to a few 1000 cm-1 for vibrational levels, therefore need higher resolution methods that tolerate fewer secondary conditions

Question 5

linear polarisation

Answer 5

electric field oscillates in a well-defined plane perpendicular to the direction of light travel

Question 6

consequences of spectroscopic probes of rotation

Answer 6

frisbee = rotation in plane containing it’s velocity, impulsive mechanism
helicopter = rotation in plane perpendicular to its velocity, complex mechanism

Question 7

effect of increasing rotation energy on reaction

Answer 7

initially decreases at low j then increases at high j

Question 8

effect of increasing rotational energy at low j

Answer 8

small Erot, major effect = stereochemical, rotational motion disrupts system from preferred angular configuration needed for reaction `

Question 9

effects of increasing rotational energy at high j

Answer 9

large Erot, major effect = energetic, rotational motion increases local velocity, gives centrifugal distortion at high j which also contributes to motion along reaction coordinate