Application of ultrasonic-assisted inclusion complex formation with α-cyclodextrin for simultaneous spectrophotometric determination of gallic acid and vanillic acids in fruit samples.

There are various methodologies to generate second-order data. Spectrophotometric method owing to its high sensitivity continues to be of wide interest to analytical chemists. Spectra recording at different interval time while the reaction is proceeded, or at different pHs, or at different concentrations of complexing agent are examples of strategies by which one can generate second-order data by the spectrophotometric method. In this work, for the first time, we employed α-CD as an inclusion complexing agent under ultrasonic irradiation for simultaneous determination of gallic acid (GA) and vanillic acid (VA). UV spectra of a mixture of two analytes were recorded as a function of α-CD concentration. A calibration set containing 9 reference samples was used to construct model using bilinear least squares/residual bilinearization (BLLS/RBL) as second-order calibration method. The predictive ability of the resulting model was validated by a test set including 5 samples. Finally, the proposed model was successfully applied to simultaneously determine the content of GA and VA in five fruit juice samples. Satisfactory results in terms of the recovery yields were obtained. In a word, UV-spectroscopy coupled with a strategy to yield a second-order data in combination to second-order calibration methods has high potential to be a simple, quick and accurate analysis procedure for the determination of various types of chemical structures in practice.

Comparison of halogen bonds in M-X⋯N contacts (M = C, Si, Ge and X = Cl, Br).

The halogen bonds (XB) formed between some Si-X- and Ge-X- (X is Cl and Br) containing molecules and NCH (as a Lewis base) have been investigated and compared with C-X⋯N halogen bond. Although, in all cases, the existence of a positive electrostatic potential (σ-hole) along the extension of M-X was responsible for halogen bond formation, multipole expansion of electrostatic potential reveals that these positive potentials originate from different atomic multipole moments. Indeed, in addition to the monopole moment of M atoms, the quadrupole moment of X in C-X molecules, the dipole moment of the halogen in Si-X molecules and both the dipole and quadrupole moments of X in Ge-X molecules are mainly responsible for the existence of the σ-hole along the extension of the M-X bond. From a different point of view, the distribution of the Laplacian of electron density shows that all the studied M-X⋯N halogen bonds can be regarded as "lump-hole" interactions; a region of charge depletion (hole) in the valence shell charge concentration (VSCC) of the halogen atom interacts with a region of charge concentration (lump) in the VSCC of nitrogen and forms a halogen bond. On the other hand, interacting quantum atoms (IQA) analysis of atomic energies indicates that, in contrast to C-X⋯N contacts, in which the interaction between halogen and nitrogen is attractive, there is a net repulsive interaction between X and N in Si-X⋯N and Ge-X⋯N complexes. Indeed, the attraction between Si/Ge and nitrogen is mainly responsible for the formation of these halogen bonds.

An ortho-rhom-bic polymorph of 2-(1,3-benzothia-zol-2-yl)-6-eth-oxy-phenol.

In the title mol-ecule, C(15)H(13)NO(2)S, an intra-molecular O-H⋯N hydrogen bond forms an S(6) ring motif. The benzothia-zole ring system and the benzene ring form a dihedral angle of 8.9 (3) Å. In the crystal, mol-ecules are linked by weak C-H⋯O hydrogen bonds, forming chains along the b axis. In addition, π-π inter-actions [centroid-centroid distances = 3.772 (4) and 3.879 (4) Å] are observed.