Classical and advanced chemical sciences
The energy and electronic parameters of the nitrogen inversion in imines Н2С=NХНn (ХНn = СН3, NH2, OH, F, SiH3, PH2, SH, Cl) have been calculated with the DFT method (B3LYP 6-311+G(d,p)) in terms of natural bond orbital. It has been established that the interactions of the nitrogen lone pair (LP) with the bond orbitals at the imino carbon atom are practically independent of the X atom and contribute to the decrease of the inversion barriers (ΔЕі≠). While nN→σ*X–H, nN↔σX–H and nN↔nX interactions substantially depend on the heteroatom type and promote the increase in the ΔЕі≠ values with the rise in electronegativity of the X atom. The contribution of the interactions of the nitrogen LP with the Rydberg orbitals of the C=N–X group atoms is small and they cannot be the main reason of the decrease in the ΔЕі≠ values when X atoms of the second period are replaced by atoms of the third period of the same group. The interactions of the LP of the X atoms and the X–H bond orbitals with the C=N bond orbitals have the main influence on the inversion barriers. The contribution of nX→π*C=N interactions to the ΔЕі≠ values is dominant. The main reason of the “anomalous” inversion barriers of N-methyl- and N-chloroformaldimines is the destabilization of inversion transition states because of the reduction in the energies of σX–H →π*C=N and nX→π*C=N interactions and the rise in the energies of nN↔nСl interactions. The contributions of electronegativity of ХНn substituents and energies of intramolecular interactions to the ΔЕі≠ values have been determined.
Keywords: Imines, inversion barriers, intramolecular interactions, electronegativity, correlations
We have synthesized 2-(4-chlorophenyl)-8-(methylthio)-6-imino-4-phenyl- 2,6,9,9a-tetrahydropyrimido[2,1-b][1,3]oxazine-7-carbonitrile (3) by the reaction of 6-(4-chlorophenyl)-4-phenyl-6H[1,3]oxazin-2-amine (2) with 2-(bis (methylthio) methylene)malononitrile in the presence of catalytic amount of potassium carbonate in DMF under reflux condition. The aminooxazine was prepared by the reaction of chalcone (1) with urea in the presence of ethanol and sodium hydroxide under reflux condition. The synthesized compounds were characterized by spectral methods. The compound (3) possesses replaceable methylthio (-SCH3) group at 8 position. The compound (3) react with various nucleophiles like substituted aromatic amines, aromatic phenols, hetarylamines and active methylene compounds to give 2-(4-chlorophenyl)-8-(substituted)-6-imino- 4-phenyl-2,6,9,9a-tetrahydropyrimido[2,1-b][1,3]oxazine-7-carbonitriles in good yields.
Keywords: Claisen-Schmidt condensation, Michael addition reaction, 2-(bis (methylthio) methylene)malononitrle, urea
Gold nanoparticles (Au NPs) coupled with 3-morpholinopropane-1-sulfonic acid (MOPS) for catalytic performance to the cyclocondensation reaction of aromatic/heteroaromatic/aliphatic aldehydes, indole and aromatic/heteroaromatic amines have been demonstrated for the first time in favour of 3-aminoalkylated indoles in ethyl alcohol at reflux temperature. Reaction conditions are just like ambient nevertheless all chemical transformations completed smoothly contributing worthwhile for the synthesis of 3-aminoalkylated indoles.
Keywords: Gold nanoparticles; catalytic performance; amino alkylated indoles; 3-morpholinopropane-1-sulfonic acid (MOPS)
Chemical and biological aspects of life
Herein, the drug delivery systems (DDS) based on nanomedicine proofed high potential and wide applicability that have distinct features related to Nano-sized. Enhancement of bioavailability and pharmacokinetics after oral administration via utility of natural/synthetic biodegradable polymeric nanomaterials. Improving biocompatibility, safety, enhanced permeability, better retention time, lower toxicity and efficient transportation of drugs to desired tissues or cells. These nanomaterials based on different types including metallic and polymeric Nano-medicine that can hydride with each other to gain new and unique features increase the efficiency of drug delivery and decrease patient compliance.
Keywords: Drug delivery system; nano-medicine; metallic nano-material; polymeric nanomaterial, polymeric structures
Gallic acid or 3,4,5-trihydroxybenzoic acid is a poly-hydroxyl compound with potential therapeutic effects in the treatment/management of oxidative stress implicated in cancers, cardiovascular and neurodegenerative diseases amongst many others. The identity, purity, integrity and suitability of the acid were ascertained and established prior to the preparation of derivatives. Furthermore, a simple titrimetric method for its assay was designed. The esterification and selective reduction of the acid led to two derivatives coded ME and MA whose identities have been established to be ethyl gallate and 3,4,5-trihydroxycyclohexylmethanol (possibly a new reduction derivative) respectively using the IR spectral technique. Gallic acid and MA demonstrated minimal antioxidant activity at IC50 of 0.76 and 0.89 μg mL-1, respectively. However, ME was remarkably active at 0.37 μg mL-1 which compare favourably with 0.34 μg mL-1 elicited by Vitamin C (a standard antioxidant drug). The obtained results indicate that esterification enhances the antioxidant activity of gallic acid.
Keywords: Gallic acid; esterification; reduction; ethyl gallate; 3,4,5-trihydroxycyclohexyl methanol
Theoretical and computational chemistry
Using the quantum-chemical calculation methods QCISD and G3, the possibility of the existence of nitrogen molecules with the composition N4, N6, N8 and N10 has been discussed. On the basis of the data obtained, the conclusion about possibility of existence of three novel polymorphic modifications of elemental nitrogen with an even number of atoms in molecules, namely N4 with rectangular and regular tetrahedron shapes, and N6 in a form remotely resembling an "open book", has been made. The values of bond lengths, valence and torsion angles, and oscillations frequencies in each of the above-mentioned forms of elemental nitrogen have been presented.
Keywords: Nitrogen modifications; molecular structure; quantum-chemical calculation; QCISD; G3.