The molecular structures and spectral properties of alpha-haloketones as well as their syntheses are analyzed and reviewed. Their reactivity towards oxygen, nitrogen, and sulfur nucleophiles, carboxylic acids, carbon nucleophiles, alkenes, and alkynes are discussed.
A novel approach to cucurbituril synthesis is described where partial substitution is introduced into cucurbit[n]uril. The identification of homologues (and their substitution) in reaction mixtures is achieved by a combination of ESMS and the use of the molecular probes (guests) 1,4-dioxane and 1,9-octanediamine. A unique symmetrical hexamethylcucurbit[3,3]uril, the major product, was isolated and characterized.
Pyrimidino[5',4'-6,5]-,pyridino[3',2'-6,5]- and pyrrolo[3',2'-5,6]4H-pyrano-[3,2c]benzopyran-6-one derivatives (5-7 and 10) could be obtained via reaction of 2-amino-4(p-bromophenyl) -3- cyano(carboethoxy)-4H,5H-pyrano[3,2-c]benzopyran-5-ones (3a,b) with a variety of reagents. Alkylation of (3b) with either 2-furoyl chloride or chloroacetyl chloride gave the 2-N-substituted derivatives (9a,b). Benzofurano[3,2-b]4H-pyran derivative (12) was also prepared. The antimicrobial activity of the prepared compounds was tested.
Acylation of 3-hydrazino-5,6-diphenyl-1,2,4-triazine (2) and hydrazine hydrate (7) with 4-aryl-1,3,7-triphenyl-8-oxa-1,2,6-triazaspiro[4.4]nona-2,6-dien-9-ones 5a,b gave the corresponding heterocyclic carbohydrazides 6a,b and 8a,b respectively. Conversion of compounds 8a,b into the versatile carbohydrazide derivatives 9a-g, 10, 13 and the related oxadiazoles 11, 12a,b was undertaken. A primary in vitro test of compound 8a (concentration 10(-4) M) showed activity against leukemia cell lines (CCRF-CEM, K-256, MOLT-4, PRMI-9226, SR).
A novel topological approach for obtaining a family of new molecular descriptors is proposed. In this connection, a vector space E (molecular vector space), whose elements are organic molecules, is defined as a "direct sum" of different R-i spaces. In this way we can. represent molecules having a total of i atoms as elements (vectors) of the vector spaces R-i (i=1, 2, 3,..., n; where n is number of atoms in the molecule). In these spaces the components of the vectors are atomic properties that characterize each kind of atom in particular. The total quadratic indices are based on the calculation of mathematical quadratic forms. These forms are functions of the k-th power of the molecular pseudograph's atom adjacency matrix (M). For simplicity, canonical bases are selected as the quadratic forms' bases. These indices were generalized to "higher analogues" as number sequences. In addition, this paper also introduces a local approach (local invariant) for molecular quadratic indices. This approach is based mainly on the use of a local matrix [M-k (G, F-R)]. This local matrix is obtained from the k-th power (M-k (G)) of the atom adjacency matrix M. M-k (G, F-R) includes the elements of the fragment of interest and those that are connected with it, through paths of length k. Finally, total (and local) quadratic indices have been used in QSPR studies of four series of organic compounds. The quantitative models found are significant from a statistical point of view and permit a clear interpretation of the studied properties in terms of the structural features of molecules. External prediction series and cross-validation procedures (leave-one-out and leave-group-out) assessed model predictability. The reported method has shown similar results, compared with other topological approaches. The results obtained were the following: a) Seven physical properties of 74 normal and branched alkanes (boiling points, molar volumes, molar refractions, heats of vaporization, critical temperatures, critical pressures and surface tensions) were well modeled (R>0.98, q(2) >0.95) by the total quadratic indices. The overall MAE of 5-fold cross-validation were of 2.11 degreesC, 0.53 cm(3), 0.032 cm(3), 0.32 KJ/mol, 5.34 degreesC, 0.64 atm, 0.23 dyn/cm for each property, respectively; b) boiling points of 58 alkyl alcohols also were well described by the present approach; in this sense, two QSPR models were obtained; the first one was developed using the complete set of 58 alcohols [R=0.9938, q(2)=0.986, s=4.006degreesC, overall MAE of 5-fold cross-validation=3.824 degreesC] and the second one was developed using 29 compounds as a training set [R=0.9979, q(2)=0.992, s=2.97 degreesC, overall MAE of 5-fold cross-validation=2.580 degreesC] and 29 compounds as a test set [R=0.9938, s=3.17 degreesC]; c) good relationships were obtained for the boiling points property (using 80 and 26 cycloalkanes in the training and test sets, respectively) using 2 and 5 total quadratic indices: [Training set: R=0.9823 (q(2)=0.961 and overall MAE of 5-fold cross-validation=6.429 degreesC) and R=0.9927 (q(2)=0.977 and overall MAE of 5-fold cross-validation=4.801 degreesC); Test set: R=0.9726 and R=0.9927] and d) the linear model developed to describe the boiling points of 70 organic compounds containing aromatic rings has shown good statistical features, with a squared correlation coefficient (R) of 0.981 (s=7.61 degreesC). Internal validation procedures (q(2)=0.9763 and overall MAE of 5-fold cro 34 degreesC) allowed the predictability and robustness of the model found to be assessed. The predictive performance of the obtained QSPR model also was tested on an extra set of 20 aromatic organic compounds (R=0.9930 and s=7.8280 degreesC). The results obtained are valid to establish that these new indices fulfill some of the ideal requirements proposed by Randic for a new molecular descriptor.
A wireless sensor network is presented for in-situ monitoring of atmospheric hydrogen concentration. The hydrogen sensor network consists of multiple sensor nodes, equipped with titania nanotube hydrogen sensors, distributed throughout the area of interest; each node is both sensor, and data-relay station that enables extended wide area monitoring without a consequent increase of node power and thus node size. The hydrogen sensor is fabricated from a sheet of highly ordered titania nanotubes, made by anodization of a titanium thick film, to which platinum electrodes are connected. The electrical resistance of the hydrogen sensor varies from 245 Omega at 500 ppm hydrogen, to 10.23 kOmega at 0 ppm hydrogen ( pure nitrogen environment). The measured resistance is converted to voltage, 0.049 V at 500 ppm to 2.046 V at 0 ppm, by interface circuitry. The microcontroller of the sensor node digitizes the voltage and transmits the digital information, using intermediate nodes as relays, to a host node that downloads measurement data to a computer for display. This paper describes the design and operation of the sensor network, the titania nanotube hydrogen sensors with an apparent low level resolution of approximately 0.05 ppm, and their integration in one widely useful device.
The relevance of polyphenols in human health is a well known fact. Prompted by that, very intensive research has been directed to get a method to detect them, which will improve the current ones. Laccase (p-diphenol:dioxygen oxidoreductase, EC 188.8.131.52) is a multi-copper oxidase, which couples catalytic oxidation of phenolic substrates with four electron reduction of dioxygen to water . A maximum catalytic response in oxygenated electrolyte was observed between 4.5 and 5.5 , while for pH > 6.9 the laccase was found to be inactive . We prepared a biosensor with laccase immobilised on a polyether sulphone membrane, at pH 4.5, which was applied at Universal Sensors base electrode. Reduction of the product of oxidation of several polyphenols, catalysed by laccase, was done at a potential for which the polyphenol of interest was found to respond. Reduction of catechol was found to occur at a potential of 200mV, which is often referred to in the literature for polyphenolic biosensors. However other polyphenols did not respond at that potential. It was observed that (+)- catechin produced a very large cathodic current when +100mV were applied to the laccase biosensor, both in aqueous acetate and 12% ethanol acetate buffer, whereas caffeic acid responded at 50mV. Other polyphenols tested were gallic acid, malvidin, quercetin, rutin, trans-resveratrol.
New derivatives of benzo-15-crown-5 with flexible appended N2O unsymmetrical Schiff bases were prepared by a two step procedure which involves: (i) preparation of N2O Schiff bases by condensation of hydrazine with salicylaldehyde, 3-methoxysalicylaldehyde or 2-hydroxy-1-naphtaldehyde and (ii) reaction of the resulting NH2 functionalized compounds with 4'-formyl-benzo-15-crown-5.
The direct electrochemistry of glucose oxidase ( GOD) was accomplished at a gold electrode modified with single-wall carbon nanotubes (SWNTs). A pair of well-defined redox peaks was obtained for GOD with the reduction peak potential at - 0.465 V and a peak potential separation of 23 mV at pH 7.0. Both FT-IR spectra and the dependence of the reduction peak current on the scan rate revealed that GOD adsorbed onto the SWNT surfaces. The redox wave corresponds to the redox center of the flavin adenine dinucleotide( FAD) of the GOD adsorbate. The electron transfer rate of GOD redox reaction was greatly enhanced at the SWNT-modified electrode. The peak potential was shown to be pH dependent. Verified by spectral methods, the specific enzyme activity of GOD adsorbates at the SWNTs appears to be retained.
Poly ( acridine red) modified glassy carbon electrode was used for the detection of dopamine in the presence of ascorbic acid in a pH 7.4 phosphate buffer solutions (PBS) by cyclic voltammetry and differential pulse voltammetry. The major difficulty of the overlapped oxidation potential of ascorbic acid could be overcome through the distinct attractive ability of poly ( acridine red) film to cationic dopamine and anionic ascorbic acid. The results showed that the dopamine anodic peak current and the concentration of dopamine had a linear relationship in the range of 1.0 x 10(-7) similar to 1.0 x 10(-4) mol dm(-3). The detection limit (S/N= 3) obtained by differential pulse voltammetry was 1.0 x 10(-9) mol dm(-3). The relative standard deviation of 10 successive scans was 2.07 % for 1.0 x 10(-6) mol dm(-3) DA. Ascorbic acid had hardly interference with the determination of dopamine. The proposed method exhibits good recovery and reproducibility.