Question

2. Explain why broad absorbances are expected for compounds containing alcohol and carboxylic acid functional groups. Draw the hydrogen bonding interaction between two ethanol molecules.

3. Draw a compound with a sterically hindered alcohol functional group. What is the most important and distinctive absorbance expected when assessing an IR of this compound?

5. Can IR spectroscopy easily be used to determine the structure of a molecule? Why or why not?

Answer 1

Solution :

2) The broad absorbances are observed for carboxylic acid and alcohols. These are due to the capability of formation of intermolecular hydrogen bonding.

The hydrogen bonding interaction between two ethanol molecules are given below.

CH3-CH2-OH ------- OHCH2-CH3

The dotted lines represents intermolecular interaction.

3) The sterically hindered alcohol is tertiary butyl alcohol.

(CH3)3C-OH === Tertiary butyl alcohol

Due to presence of bulky methyl groups, the hydrogen bonding ability of OH group decreases and hence broad absorption is not observed.

4) Yes, IR spectrum of the organic compounds are easily explained by the IR spectrum because it help to explain the functional groups present in the desired molecule.