Near infrared spectroscopy of organic acids: comparing O [sbnd]H and C [sbnd]H oscillator frequencies and intensities

Abstract

This work investigates the vibrational spectroscopy of a series of organic acids, CH 3(CH 2) n COOH ( n = 1–5), previously unobserved in the IR and near-IR (2000–15 000 cm −1). The work obtains frequencies and relative intensities for all O H and C H stretching transitions. Comparison of the frequencies and intensities of C H and O H stretching transitions reveal interesting trends in acid chain length that are discussed. Literature values for acetic acid (CH 3COOH) and formic acid (HCOOH) are used to gain a broader understanding for the spectroscopy of the organic acids CH 3(CH 2) n COOH. The observation of several combination bands involving the C H and O H stretching vibrations and possible rotational isomer and hot band transitions are reported.