For January

Question 1

What is the equation for the population of ground state vs excited state for vibrational?

Answer 1

Ni/Nj = exp (-change in energy/kT)
where change in energy is upper - lower energy level

Question 2

How is NMR data generated

Answer 2

Fourier transform (separation of data according to frequency) from FID to Frequency Domain

Question 3

What is the effect of HB on coupling

Answer 3

HB do not experience/effect coupling of other CH bonds because in solution they are constantly moving (dynamic) thus exchanges between energy levels are too fast and are averaged.

Question 4

What is the resonance frequency equation?

Answer 4

v = (gy ratio x B0) /2 pi

Question 5

What is the equation for energy change between spin states

Answer 5

E = h x resonance frequency

Question 6

Coupling constant (J equation)

Answer 6

J = frequency of spectrometer x difference between chemical shift values

Question 7

What does the intensity of an EM wave absorption depend on

Answer 7

Likelihood of transition, population of initial state, concentration of sample

Question 8

What are the selection rules for rotational spectroscopy

Answer 8

1. Must have permanent dipole
2. Energy levels can only change by J +/-1

Question 9

What are the 2 types of symmetric roots and which value of inertia is bigger

Answer 9

Oblate: equivalent are smaller (benzene)
Prolate: equivalent are bigger (2 double bonded carbons)

Question 10

What is the Jmax equation

Answer 10

Jmax = ( kT/2hBc)^1/2 - 1/2

Question 11

What is the centrifugal force equation for real bond distortion

Answer 11

Fcent = mass x angular velocity x interatomic distance

Question 12

What is the equations for degrees of vibrational freedom for linear and non linear molecules

Answer 12

Linear: 3N-5
Non-linear: 3N-6

Question 13

What are the selection rules for vibrational spectroscopy?

Answer 13

1. Change in dipole moment required
2. Harmonic is J+/-1 (not true for unharmonic oscillator)

Question 14

How does measuring IR in neat and dilute solution affected broadness of band

Answer 14

Dilute solution has less HB, thus sharper peak

Question 15

What is strokes shift

Answer 15

Shift between purely electronic transitions

Question 16

What are the species that absorb UV/visible light called?

Answer 16

Chromophores

Question 17

Do sigma bonds or pi bonds require more energy for electronic transitions

Answer 17

Sigma bonds because the energy difference between bonding and antibonding is larger than

Question 18

What is the absorbance equation

Answer 18

A = ecl (l in cm, c in mole/L)
= log (intensity of incident light / intensity of transmitted light)

Question 19

what are the only transitions for hydrocarbons that can be detected by UV-vis spectroscopy?

Answer 19

non bonding to pi antibonding
pi bonding to pi antibonding

Question 20

What is the effect of increasing conjugation called?

Answer 20

Bathchromatic/redshift due to antibonding and bonding energy levels being closer together

Question 21

How was the first synthetic dye discovered and what is it called?

Answer 21

Mauevine A is the first industrially made dye and it was made through synthesis of Quinine (treatment for malaria)

Question 22

What’s isosbestic point?

Answer 22

When absorption or transmission is the same regardless of what species is present (for UV vis)

Question 23

What is the eq for energy change in NMR spec

Answer 23

E = (h x gyro ratio x B0) / 2pi

Question 24

Eq for Vobs (resonance frequency

Answer 24

Vobs = (gyro ratio x Beff)/2 pi

Question 25

What’s the eq for beff

Answer 25

Beff = B0 ( 1- shielding constant)

Question 26

Moment of inertia equations

Answer 26

I = no of element x mass x distance^2 or reduced mass x distance^2

Question 27

Eq for Energy difference between rotational states

Answer 27

E (cm^-1) = 2B (J+1)
use this if using real data (the other is energy of orbital but the spectra measures the difference between energy levels)

Question 28

Eq for population of rotational energy levels

Answer 28

= (2J + 1) x exp (- e in joules / kT)

Question 29

Eq for energy difference of non rigid rotor

Answer 29

2B (J+1) - 4D (J+1)

Question 30

Frequency of vibrations equation

Answer 30

v = ( force constant / effective mass ) ^1/2 x 1/2pi

Question 31

What are the selection rules for electronic spectroscopy

Answer 31

1. N can be any value
2. Must have l +-1 transition (additional or loss of node each time)

Question 32

What is the difference between overtones and hot bands

Answer 32

Overtones: Same starting point
Hotbands: same difference

Question 33

Moment of inertia for triatomic (same molecule on either end and different molecules on either end)

Answer 33

1. 2 x ma R^2
2. • (m1R1 - m2R2) ^2 / total mass of all 3

Question 34

What are the 2 types of energy coupling and how do they work?

Answer 34

1. Vibrational and rotational: change in centrifugal force as a molecule rotates changes vibrational modes
2. Vibrational and electronic: different vibrations (bonds lengths etc.) change the size of particle in a box, thus different electronic energy levels or different electronic transitions have different electron distributions so vibrational modes change

Question 35

What is the equation for energy difference of overtones?

Answer 35

hv x (1- 2xa) 0-1
2hv (1-3xa) 0-2
etc…

Question 36

how do double bonds effect NMR spectrums

Answer 36

Lack of rotation so loss of symmetry if different substituents are on the other side of the double bond