l-Leucinamide hydrogensquarate: spectroscopic and structural elucidation

Abstract

The hydrogensquarate [LeuNH(2)] (HSq) of L-leucinamide has been synthesized and its structure has been determined by single crystal X-ray diffraction. A three dimensional network is formed by hydrogen bonds with participation of the O=C-NH(2) function, the hydrogensquarate ion and the N(+)H(3) group [NH(2)...O=C((Sq)) (2.840 and 2.749 A), ((Sq))OH...O=C(NH(2)) (2.618 A), NH(3) (+)...O=C((Sq)) (3.246, 2.804 and 2.823 A)], respectively. A theoretical approximation of the electronic structure was carried out by means of ab initio UMP2 and MP2 level of theory at the 6-311++G** basis set. The IR-spectroscopic assignment in the solid-phase was obtained by linear-polarized IR-spectroscopy of oriented samples as colloid suspensions in a nematic host and application of the reducing-difference procedure for the interpretation of polarized IR-spectra.

Structural, spectroscopic and theoretical study of novel ephedrinum salt

“…However the bands at 1075 and 739 cm À1 could belong to different symmetry classes. If we have local C 2v symmetry they belong to A 1 , while in the case of C 2v * -to B 2 , respectively [10][11][12][13][14][15][16][17][18]. In our case, the elimination of the last bands with the 8a one at equal dichroic ratio shows that we could describe the aromatic fragment in local C 2v symmetry.…”

“…In the case of the different oriented molecules, the theory says that the components have different dichroic ratio in corresponding polarized IR-LD spectrum. That is why we can assign the components as a result of the Davydov's splitting effect [12][13][14][15][16][17][18][19][20]. On the other side, the application of the reducing difference procedure for polarized IR-LD spectra interpretation show that with the elimination of the band at 1604 cm À1 (Fig.…”

“…S3) the disappearance of the bands occur at 1492, 1155, 1085 and 739 cm À1 , respectively. Using the theory [12][13][14][15][16][17][18][19][20], the elimination of the given band leads to disappearance of the IR bands possessing same symmetry class like the eliminated band. As far as the IR band at 1604 cm À1 belongs to A 1 symmetry class it is expectable that the bands at 1492 and 1155 cm À1 will be eliminated.…”

“…The theoretical approach, experimental technique for preparing the samples, procedures for polarized IR spectra interpretation and the validation of this new linear-dichroic infrared (IR-LD) orientation solid-state method for accuracy and precision have been presented. The influence of the liquid crystal medium on peak positions and integral absorbances of the guest molecule bands, the rheological model, the nature and balance of the forces in the nematic liquid crystal suspension system and the morphology of the suspended particles have also been discussed [12][13][14][15][16][17][18][19][20].…”

“…As far as the IR spectroscopy, it is one of the powerful methods for the elucidation of the relationship between structure and properties, the detailed analysis in this respect is reasonable. That is why we present an IR spectroscopic and structural elucidation of the neutral ephedrine hemihydrate (1) and its violurate salt dihydrate (2), depicted in Scheme 1, using the powerful technique for amino acid analysis and small biologically active molecules [12][13][14][15][16][17][18][19][20], linear polarized IR spectroscopy of oriented colloid suspensions as well as single crystal X-ray diffraction. The quantum chemical calculations were also performed with a view to obtain the preferable conformations of the protonated ephedrine molecule and its vibrational properties.…”