FT-infrared study of the interaction between all-trans retinylidene isopropylamine and model proton donors

Abstract

The interaction between all-trans retinylidene isopropylamine (tRiPA) and phenols covering a large pKa domain is investigated by FT-infrared spectrometry. For phenols having pKa between 10.2 and 8.18, only normal OH … N hydrogen bonds are formed. The thermodynamic parameters (K, −ΔH, −ΔS0) determined in carbon tetrachloride solution show that tRiPA possesses a good proton acceptor ability. The spectral characteristics (frequency and integrated intensity) of the νC=N vibration are also investigated. From a pKa of 6, proton transfer takes place. The proton transfer constants determined in 1,2-dichloroethane are linearly related to ΔpKa (pKa of the protonated base minus pKa of the phenol). Comparison with previously studied imine systems shows that the proton transfer constant increases with the number of C=C double bonds in the base.

Vibrational spectroscopic studies of hydrogen‒bonded complexes between 2,5‐dihydroxy‐P‐benzoquinone and amines

“…in the range 4000-400 cm −1 , where A is the absorbance and ν is the wave number. The integrated intensities of the protonic vibrations were computed with a reproducibility of 3% utilizing the equation [25,26]…”

“…Therefore it seemed justified to carry out further IR spectra for hydrogen-bonded complexes in the solid state especially on interesting H-bonded molecular complexes between dihydroxyp-benzoquinone and amines. The integrated intensity for many hydrogen bonded systems were estimated in solution [25] and in polyethylene matrix [26] while its estimation in the solid state is not reported.…”