Question

a. How could you use IR spectroscopy to determine whether the following reaction had occurred?

b. After purifying the product, how could you determine whether all the ${\mathbf{NH}}_2{\mathbf{NH}}_2$had been removed?

Short answer

a. If this particular reaction has happened, then the absorption band at$1700{\mathrm{cm}}^{-1}$ because of the carbonyl group and at$2700{\mathrm{cm}}^{-1}$ due to the aldehyde C-H bond of the reactant would have decreased.

b. If all the${\mathrm{NH}}_2{\mathrm{NH}}_2$ has been removed, there would be no N-H absorption at $3400{\mathrm{cm}}^{-1}$.

Step-by-step solution

Step-by-step-solutionStep 1: IR spectroscopy

The stretching of a bond increases the distance between the atoms thereby increasing the dipole moment. The absorption intensity depends on the size of this change in dipole moment. The absorption is more intense if there is a significant change in dipole moment.

Using IR spectroscopy to determine whether the following reaction has occurred

a. If this particular reaction has happened, then the absorption band at $1700{\mathrm{cm}}^{-1}$because of the carbonyl group and at$2700{\mathrm{cm}}^{-1}$ due to the aldehyde C-H bond of the reactant would have decreased. These absorptions bands disappear if all of the aldehyde has reacted.

b. If all the${\mathrm{NH}}_2{\mathrm{NH}}_2$ has been removed, there would be no N-H absorption at $3400{\mathrm{cm}}^{-1}$.