An introductory undergraduate physical organic chemistry exercise that introduces the harmonic oscillator's use in vibrational spectroscopy is developed. The analysis and modeling exercise begins with the students calculating the stretching modes of common organic molecules with the help of the quantum mechanical harmonic oscillator (QMHO) model.

Explores the applicability of Mulliken's united atom model to a variety of chemical systems and demonstrates its value as a teaching tool. Considers applications to first row hydrides, compounds of the first and second periods, heavy atoms, and cluster systems. (MVL)