Raman Optical Activity and Raman Spectra of Amphetamine Species—Quantum Chemical Model Calculations and Experiments

Abstract

Theoretical calculations and preliminary measurements of vibrational Raman optical activity (ROA) spectra of different species of amphetamine (amphetamine and amphetamine-H + ) are reported for the first time. The quantum chemical calculations were carried out as hybrid ab initio DFT-molecular orbital calculations by use of the Gaussian 03W program, based on complete geometry minimizations of the conformational energy of the S-(+)-amphetamine molecule, the S-(+)-amphetamine-H + ion, and the R-(-)-amphetamine molecule. Following this, harmonic frequency calculations have been made, providing information about the cation vibrational bands, expected in salts of single anions (chlorides) as well as in salts of anions with internal bonds (sulfates, hydrogen phosphates, etc.). It shows that the kind of anion should be given better attention, as so far it has often not been the case, when the spectra are employed for identification purposes. The DFT calculations show that the most stable conformations are those allowing for close contact between the aromatic ring and the amine hydrogen atoms. The internal rotational barrier within the same amphetamine enantiomer has a considerable influence on the Raman and ROA spectra. As predicted the experimental ROA spectra were found to depend on the chirality. Two street samples, provided by the London Police, were also measured and compared to the calculated ROA spectra. The street samples were found to contain different enantiomers of the protonated amphetamine-H + sulfate. According to the present study the AMPH + ion in aqueous sulfate solution seems to adopt a conformation in which the phenyl and ammonium groups are in transpositions, similar to what has been found in the solid state.

Investigation ofL(+)-Ascorbic acid with Raman spectroscopy in visible and UV light

“…The reason is that differences in the conformation geometry are substantially reflected in the couplings among the vibrational modes, leading to noticeable differencies in frequencies and intensities. This is similar to what has been found for other molecules such as amphetamine (82,83) or for ionic liquids (84,85).…”

“RaMassays”: Synergistic Enhancement of Plasmon-Free Raman Scattering and Mass Spectrometry for Multimodal Analysis of Small Molecules

“…Figure 3 shows the Raman spectra of (1R, 2S)-(-)-ephedrine and amphetamine, two important alkaloids related by the same phenethylamine skeletal structure. Both spectra display almost the same modes, which are related to the benzene ring breathing vibrations, the only difference being their relative intensity 41 42 .…”

Construction of Raman spectroscopic fingerprints for the detection of Fusarium wilt of banana in Taiwan

“…The spectral region at 1003 and 1113 cm −1 can mainly be attributed to the C-C aromatic ring of phenylalanine and deformational vibration of tryptophan [32], respectively, and the bands at 1255 and 1289 cm −1 may be attributable to the amide III of collagen [30] and C-C stretching of unbranched saturated fatty acids [34], respectively. The peaks of 1346 and 1639 cm −1 were possibly related to the CH 2 of tryptophan [32] and C-C stretching ring or in-plane C-H bending, respectively [37]. In addition, we tested Bd (YJC-F004) and Dt (PM-YJL-F119) on potato dextrose agar, yeast peptone dextrose agar, and V8 agar.…”