Spectroscopy Worksheet printable pdf download

Spectroscopy Worksheet

CHEM1102 Worksheet 4: Spectroscopy Workshop (1)

This worksheet forms part of the ‘Spectroscopy Problem Solving Assignment’ which represents 10% of

the assessment of this unit. You should use the support material on eLearning alongside this worksheet

and your lecture notes. The assignment is assessed through online quizzes and must be completed by the

end of week 7. Spectroscopy Workshop (2) will follow in the week 5 tutorial.

Model 1: Infrared (IR) Spectroscopy

You have seen in lectures how bonds stretch and bend. A light wave of the correct frequency will be in

resonance with a bond in motion and transfer its energy to this motion, like a parent pushing a swing. Light

absorbed by the molecule in this manner falls in the infrared range. The frequencies at which some bonds

stretch is quite similar in different molecules so IR spectroscopy can be used to identify bonds, and hence

functional groups, in a molecule.

The table below lists IR absorption frequencies for some common bonds found in organic molecules:

alcohol

alkane

carbonyl

amine

alkyne

Bond

O-H

C-H

C=O

N-H

C≡C

Absorption Range

3200-3650

2840-3000

1690-1760

3100-3500

2100-2260

-1

(cm

)

(strong, broad)

(strong)

Critical thinking questions

Use the characteristic stretching frequencies to match the four compounds below to their IR

spectrum.

Spectroscopy Worksheet