in this study the chemical properties of b6c4si and c16 clusters connected vitamin c have been investigated using density functional theory (dft). nmr parameters and homo- lumo gap energy are calculated by using density functional method (b3lyp) with 6-311g* basis set. calculations show that homo- lumo gap energy of vitamin c decreases after connecting to b6c4si or c16 cluster decreasing of hom...

the 1h and natural-abundance 13c-nmr spectra of 1-thiacyclooctan-3-one (1) have been measured from 25 to -100°c. coalescence is observed in the 1h-nmr spectra of (1) at about -80°c, and attributed to ring inversion in a boat-chair conformation, which is the predominant conformation of (1). the free energy of activation (dg¹) for this process is 9.2±0.2 kcal/mol. the 13c-nmr spectra of (1) is te...

body's iterative force-field computer program has been used to calculate strain energies in cyclooctanone (i). 348 mhz 1h nmr spectra of (i) have been investigated over the temperature range of 25° to -160°c. two conformation processes affect the 1h nmr spectrum of (i). iterative force-field calculations on the conformations and conformational interconversion paths of (i) give results consisten...

p53 is one of the gene that has important role in human cell cycle and in the human cancers too.models of codon substitution make it possible to separate mutational biases in the dna fromselective constraints on the protein, and offer a great advantage over amino acid models forunderstanding the evolutionary process of proteins and protein-coding dna sequences. in thiswork, we investigated abou...

the potential of tobacco waste as a viable source of medicinally important flavonoids like rutin has been investigated. three flavonoids, apigenin, quercetin and rutin, have been isolated from waste tobacco leaves, and their identities have been confirmed by uv-visible, 1h-nmr and 13c-nmr spectroscopy. by using analytical hplc, the amount of rutin present in the tobacco leaves, before and after...

over the past decade, the chemical behavior of flavonoids as antioxidants has become the subject ofintense experimental research. in this paper, we use a quantum-chemical approach to shed light on thereactivity of four poly phenols, benzoic acid, vanilic acid, gallic acid and flavone . in order to establishthe most efficient theoretical methodology, different methods, either hartree—fock-based ...

a quantum chemical investigation was carried out to study the properties of intermolecular f•••f, br•••br and br•••o interactions in crystalline 1-bromo-2,3,5,6-tetrafluoro-nitrobenzene (bfnb). this system was selected to mimic the halogen-halogen as well as halogen bonding interactions found within crystal structures as well as within biological systems. we found that fluorine atoms have weak ...

magnesium oxide nanoclusters have attracted much attention due to their potential applications to catalysis and novel optoelectronic materials. in the present study, we have studied the electronic and magnetic properties of the stoichiometric magnesium oxide nanoclusters (mgo)n  for n = 2-20. although the binding energy increases with the size of the cluster, it  reaches the asymptotic limit of...