Electronic spectroscopy

Question 1

Where do electronic transitions occur?

Answer 1

Atomic orbitals in atoms

Molecular orbitals in molecules

Question 2

Where do electronic transitions occur in alkanes?

Answer 2

Sigma to sigma star

Question 3

Where do electronic transitions occur in carbonyl compounds?

Answer 3

Sigma to pi star

n to pi star

Question 4

Where do electronic transitions occur in alkenes, alkynes and carbonyl compounds?

Answer 4

pi to pi star

Question 5

Where do electron transitions occur in nitrogen, sulfur, oxygen and halogen compounds?

Answer 5

n to sigma star

Question 6

What is n?

Answer 6

Non-bonding orbital

Question 7

Which orbitals are filled?

Answer 7

Sigma
Pi
n

Question 8

Which orbitals are empty?

Answer 8

Pi star

Sigma star

Question 9

What happens to the wavelength if the amount of conjugation increases?

Answer 9

Becomes longer

Question 10

What is a chromophore?

Answer 10

A region in a molecule where the energy difference between two different molecular orbitals falls within the range of the visible spectrum

Question 11

What happens to visible light that hits the chromophore?

Answer 11

Absorbed by exciting an electron from its ground state into an excited state

Question 12

What are the two forms chromophores arise in?

Answer 12

Conjugated pi systems

Metal complexes

Question 13

What causes the conformational change of he molecule when hit by light?

Answer 13

Chromophore

Question 14

What is pi conjugation?

Answer 14

Alternating single and double bonds which allow for electrons to be transferred from a filled orbital to an empty orbital

Question 15

What do selection rules tell us?

Answer 15

If a reaction is likely and favourable

Question 16

What factor affects the magnitude of e and why?

Answer 16

Orbital overlap

Pi and pi star are in the same geometric space so they have a large value of e

Question 17

What does gas phase spectra show?

Answer 17

Vibrational structure

Question 18

Equation for work done?

Answer 18

Force x distance = work done

Question 19

What is the equation for the harmonic oscillator?

Answer 19

V = 1/2π √k/μ

Question 20

What is the zero-point energy equal to?

Answer 20

(1/2)hv

Question 21

What is the equation is for Eᵥ?

Answer 21

Eᵥ = hv(v+1/2)

Question 22

What does a full quantum mechanical treatment do?q

Answer 22

Leads us to particular wavefunctions and particular energies which go with the wavefunctions

Question 23

What is anharmonicity?

Answer 23

Deviation from the system from harmonic oscillator

Question 24

What is morse potential?

Answer 24

Convenient model for the potential energy of a diatomic molecule

Question 25

What happens to the higher energy level on a potential energy surface graph?

Answer 25

They become closer together

Question 26

when does the simple harmonic oscillator break down?

Answer 26

Short bond lengths

Question 27

What happens to the force between two atoms when you try and separate them?

Answer 27

it goes down

Question 28

What is the force like at infinite separation?

Answer 28

There is no force