New experimental results are reported on molecular interactions in the n-ethylamines and 2-nitropropane (2-NP)/n-ethylamine mixtures studied by Raman spectroscopy under pressure in a diamond anvil cell (0-50 GPa) and, at ambient pressure, by infrared spectroscopy. Modifications of the infrared spectra in 2-NP in presence of triethylamine (TEA) or diethylamine (DEA) have been observed at ambient pressure and interpreted as a specific molecular interaction. High-pressure fluorescence in the vicinity of the liquid-solid phase transition of the 2-NP/DEA and 2-NP/monoethylamine mixtures, is highlighted and discussed.