Organic Analysis - Infrared Spectroscopy

Question 1

How does Infrared (IR) Spectroscopy work?

Answer 1

1. A beam of IR radiation is passed through a sample of a chemical
2. The IR radiation is absorbed by the covalent bonds in the molecules, increasing their vibrational energy
3. Bonds between different atoms and bonds in different places in a molecule absorb different frequencies of IR radiation

Question 2

What does an Infrared Spectrometer produce?

Answer 2

A graph that shows you what frequencies of radiation the bond in the molecules are absorbing

Question 3

What can an Infrared Spectrometer be used for?

Answer 3

Identifying functional groups in a molecule

Question 4

What do the peaks on a Infrared Spectrometer show you?

Answer 4

Where radiation is being absorbed

Question 5

What is the fingerprint region?

Answer 5

The region between 1000cm-1 and 1550cm-1 on the spectrum

Question 6

How can you use the fingerprint region?

Answer 6

Check this region of an unknown compound’s IR spectrum against those of known compounds. If it matches one of them, you know what the molecule is

Question 7

What can Infrared Spectroscopy be used for?

Answer 7

Assess how pure a compound is and identify impurities, which produce extra peaks in the fingerprint region

Question 8

How is Infrared Spectroscopy and Global Warming linked?

Answer 8

1. The Sun emits mainly UV radiation which is absorbed by the Earth’s surface and re-emitted as IR radiation
2. Molecules of greenhouse gases have bonds that are good at absorbing infrared energy
3. So if the amounts of theses gases in the atmosphere increase, more IR radiation is absorbed, leading to global warming
4. The more IR radiation a molecule absorbs, the more effective they are as greenhouse gases