The carbonyl stretching vibration of acetone is reported in infrared spectroscopy at…
CHEMISTRY · Multi-part · A Level · Chemistry · Organic analysis and spectroscopy · Organic analysis and spectroscopy
Problem
The carbonyl stretching vibration of acetone is reported in infrared spectroscopy at a wavenumber of 1.75 × 10³ cm⁻¹.
(a) Convert this wavenumber to its corresponding wavelength in meters.
(b) Calculate the energy of a single photon with that wavelength in joules, then convert the energy to kJ mol⁻¹.
(c) At room temperature (298 K), the average thermal energy per mole is approximately 2.48 kJ mol⁻¹. Compare this thermal energy with the photon energy found in part (b) and discuss whether thermal motion alone is likely to populate the carbonyl stretching excited state.
(d) Based on the magnitude of the photon energy, classify the transition (rotational, vibrational, or electronic) and justify your answer.