Between C=O and C―S, which is expected to vibrate at a higher wavenumber?

Identify the bond in each pair that absorbs at a higher wavenumber.
i) N–H stretch or N–H bend
ii) C–F stretch or C–I stretch

Explain why the C–N absorption of an amine occurs at 1020 cm^–1 while the C–N absorption of an amide occurs at 1400 cm^–1.

Rank the C=O absorption of the following compounds from highest to lowest frequency.

Consider the C–N bonds in N-methylacetamide. Rank them by i) increasing bond length and ii) increasing stretching frequency.

An O—H bond, electronically similar to an O—D bond, has an equivalent spring constant value, k. Use the formula for infrared absorption frequency f given below: 

Where k is the spring constant, and μ is the reduced mass, to calculate the IR absorption frequency of an O—D bond. Use the O—H IR frequency value as 3300 cm⁻¹.

If you run an IR spectrum by dissolving the compound in a solvent with D₂O as an impurity, state the functional group whose vibrational frequency can be present in the same region as the O—D stretch.