Question

Given a FTIR spectrum of C3H8O below, assign appropriate vibrations of the marked peak.

3) Given a FTIR spectrum of C3H20 below, assign appropriate vibrations of the marked peaks. (2pt)

Answer 1

Solution

Here given molecular formula=C₃H₈O

Hence, Degree of unsaturation= C+1-H/2

=3+1-8/2

   =0

So the compound with given molecular formula contains no any double bond

Hence feom the given IR spectrum assignment of vibration of the marked peak is given in below table

• IR spectrum table

Absorption	Appearance	Functional group	compound class
~3400 cm-1	Strong, broad	O-H stretching	Alcohol
~2950 cm-1	Medium	sp3 C-H stretching	alkane