Question

1. Indicate the representative/characteristic peaks for the following compounds and where will they fall (approx. wave No.) on the IR spectra.

a) CH3 OH

b) CH2= CH2

Answer 1

a) In case of CH3OH a broad/sharp peak at ~3200-3600 cm-1 with strong intensity for O-H will appear (broadness will depend on the extent of hydrogen bonding present within the molecule, less H-bonding, sharp peak). Additionally, stretching at ~2800-2950 cm-1 would appear for Csp3-H bonds.

b) There will be peak at 3010-3100 cm-1 for =C-H stretching with medium intensity along with 1620-1680 cm-1 for C=C bond but this may not appear because of symmetry in molecule.