Wyniki wyszukiwania - BazTech

Ograniczanie wyników

Powiadomienia systemowe

Sesja wygasła!

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Sortuj według:

Ogranicz wyniki do:

Determination of the lipophilicity of selected isoquinoline alkaloids by RP-TLC

Waksmundzka-Hajnos M., Matosiuk D., Petruczynik A., Kijkowska-Murak U.

Acta Chromatographica

2008

Vol. 20, no. 4

563-573

Nine alkaloids were chromatographed by reversed phase (RP) TLC on RP-18 with aqueous acetone or aqueous dioxane mobile phases. A variety of mobile phase additives (ammonia, diethylamine (DEA), tetrabutylammonium chloride (TBA-Cl)) were used to suppress ionization of the alkaloids and/or reduce ionic interactions with surface silanol groups. Ion-pair (IP) RP-TLC was also performed with aqueous acetone mobile phases and reagents such as pentane sulphonic acid (PSA), octane sulphonic acid (OSA), or di-(2-ethylhexyl)orthophosphoric acid (HDEHP) as mobile phase additives. In these systems retention of the alkaloids was determined using mobile phases with different modifier concentrations. Relationships between R M and modifier concentration were sought. A linear semilogarithmic equation was fitted to experimental data and used to obtain lipophilicity values R MW ( R M for pure water), the slope ( S ), and φ 0 , the intercept with the x -axis. The retention of standards with known lipophilicity log P was then determined using the chromatographic systems described above and R MW values were calculated. From these experimental data equations relating log P and R MW were created for each system separately and these equations were used to estimate log P exp values for the alkaloids. log P exp , slope ( S ), and φ 0 values obtained by use of different TLC systems were also correlated.

Structural Studies of 1-Aryl-2-aminoimidazolinium Bromides: Focus on Tautomer Preference of the 2-Aminoimidazoline Moiety in the Solid State

Dobrowolski M., Cyrański M., Pisklak M., Wawer I., Matosiuk D.

Polish Journal of Chemistry

2007

Vol. 81, nr 5-6

1037-1048

The crystal structures of five 1-(4-X-phenyl)-2-aminoimidazolinium bromides (where X = -OCH3, -CH3, -H, -Cl and -NO2) were determined by X-ray crystallography with the aim to investigate the tautomer preference of the aminoimidazoline moiety in the solid state. The molecular structures clearly indicate that only the ring nitrogen is protonated. The crystals are stabilized by interactions between the hydrogens of the amino group (also NH fragment of the imidazoline ring) and bromide anion. In the case of the nitro derivative additional strong hydrogen bonds are a consequence of the presence of water molecule in the crystal lattice. The methoxy and nitro derivatives were studied by 15N CP/MAS NMR and the analysis of the tautomer preference was completed by ab initio calculations at the B3LYP/6-311+G** level.