1. 2) Infra-red spectroscopy
The Energy of molecular vibrations.
To be IR active, a molecule must undergo a change in dipole.

2. E=hf (E=h) Meaning the electromagnetic spectrum covers ALL energy ranges.
IR spec

4. IR spec
……Zooming in on the IR range… the energy of molecular bends and stretches

5. IR spec NOT ON SYLLABUS:
What’s a degree of freedom? A way in which molecule can undergo a vibration (bend or stretch)

6. I.R. – degrees of freedom E.g. CO2 (a linear molecule)
n=3 (the number of atoms)
3n-5 = 4 “modes” of vibration

7. IR spec
Vibrations (bends and stretches) of CO2

8. IR spec

9. IR spec

10. IR spec
Can also bend in and out of the plane of the paper. This is the second way of bending

11. IR spectrum of CO2 3n-5 (linear) = 4
science.widener.edu/svb/ftir/ir_co2.html

12. IR spec
CHART of IR absorbancies
Various IR

13. IR spec

14. IR spec
A sample IR spectrum of octane (nujol)

15. IR spec Alkanes , Alkenes, Alcohols Halogen, Aldehydes,
Ketones, Esters, Carboxylic acids,
Aromatics, Amines.
Chemguides: propan-1-ol, (2-ol next page)
D:\Users\user\Documents\--- A-Level and Science\Mike

16. IR spec