11.3 Spectroscopic identification of organic compounds

Question 1

What is IHD?

Answer 1

IHD = Index of hydrogen deficiency
This is the same as degree of unsaturation

Question 2

What is the function of IHD?

Answer 2

IHD can be used to determine from a molecular formula the number of rings or multiple bonds in a molecule

Question 3

What is the degree of unsaturation used for?

Answer 3

It is used to calculated the number of rings and π bonds present in a structure where:
- 1 double bond = 1 IHD
- 1 triple bond = 2 IHD
- 1 ring = 1 IHD
- 1 aromatic ring = 4 IHD

Question 4

List the 2 ways that IHD can be worked out from

Answer 4

1. From the structure
2. From the molecular formula

Question 5

What is the formula for IHD when it is worked out from the molecular formula?

Answer 5

IHD = (0.5)(2c + 2 - h - x + n)

c = Carbon
h = Hydrogen
x = Halogens
n = Nitrogen

Question 6

Why is oxygen not found in the IDH formula?

Answer 6

Oxygen forms 2 bonds therefore it has no impact to the IDH

Question 7

What is Planck’s equation and what are the units?

Answer 7

E = hv = (hc/lambda)

E: Energy of electromagnetic radiation (measured in J)
v: Frequency (measured in Hz)
h: Plank’s constant
c: Speed of light
lambda: wavelength (measured in m)

Question 8

What is Plank’s constant?

Answer 8

6.63 x 10^-34 J s
Given in data booklet

Question 9

What is the speed of light?

Answer 9

3.00 x 10^8 m/s
Given in data booklet