UV/IR spectroscopy

Question 1

What is the relationship between wavelength and Energy

Answer 1

Longer wavelength = Less energy/radiation

Question 2

What kind of vibrations can IR absorb

Answer 2

Asymmetric vibrations that cause change in dipole moments

Question 3

What is wave number

Answer 3

An interchangable term for frequency in cm-1

Question 4

Hooke’s law

Answer 4

u = 1/2π x (k/μ)^1/2

Question 5

What does a higher wave number correlate to

Answer 5

• Stronger bond
• Higher Force constant
• Lower molecular mass

Question 6

How does the presence of an electron withdrawing group affect IR spectroscopy

Answer 6

It increases the force constant and therefore increases the wave number value

Question 7

How does the presence of conjugation affect IR spectroscopy

Answer 7

It reduces the frequency and therefore decreases bond strength resulting in a lower wavenumber

Question 8

How does the presence of an electron donating group affect IR spectroscopy

Answer 8

Reduces the force constant thereby correlating to a lower wavenumber

Question 9

C-H bond Wavenumber value

Answer 9

~3000cm-1

Question 10

C=O wavenumber value

Answer 10

~1700cm-1

Question 11

What does a heteroatom(N,Cl,O)-H bond look like in a IR spectroscopy

Answer 11

> 3000cm-1