JOURNAL OF SCIENCES (ISLAMIC AZAD UNIVERSITY)
Year:2005 | Volume:15 | Issue:56|Papers Count:9

Acid anilides I are an important class of organic compounds. When R2#R3 acid anilides I are chiral and they have optical activity.Racemization in these compounds takes place by rotation about CAr-N bond. In room temperature rotation about this bond needs high energy barrier, therefore racemization don't occur. If compound I contain diastereotopic groups, For example R4=CH2C6H5, in 1HNMR spectra an AB quartet pattern is appeared. When temperature is increased the rotation about CAr-N bond becomes rapid on the NMR time scale, coalescence of the AB signal should be observed. The barrier to rotation about the CAr-N bond therefore can be obtained by the dynamic NMR technique. We study and measure of the energy barrier in the some derivatives of acid anilides I. We found that semiempirical SCFMO calculations can help to chemists for study of energy barrier in acid anilides I. Energy barrier for racemization of compound II (when X=H) via DNMR is 21 kcal mol-1. AM1 method calculate this barrier to 20.3 kcal mor-1. Electron withdrawing groups in the para-position (for example NO2 or Br) decrease the energy barrier of racemization for compound II (when X=NO2) this barrier is 18.9 kcal mor-1 and for compound II (when X=Br) this barrier is 20.6 kcal mol-1. The AMl method calculates these energy barriers 19.2 and 19.7 kcal mol-1 respectively. We report a study of transition state of racemization process that was calculated by AMl methods.

A proton NMR method for the determination of solvation numbers of alkaline earth cations with hexamethyl phosphoramide in nitromethane as diluent is described. The method is based on monitoring the resonance frequency of solvent's protons as a function of solvent to metal ion mole ratio at constant metal ion concentration. The average solvation number of cations, n, at any solvent/metal ion mole ratio was calculated from the NMR chemical shift-mole ratio data and was plotted against the mole ratio values. The solvation numbers of alkaline earth cations were obtained from the limiting values of the corresponding n, vs. mole ratio plots.The effect of presence of water on the solvation numbers of alkaline earth cations with HMP A was studied. In this case, variations in the resonance frequency of H2O protons brought about upon titration of the cations by HMP A was used to estimate the solvation number of cations with these solvents.

Transition metal/Y zeolites were prepared by microwave solid state and aqueous solution ion exchange methods in three concentration (0.1, 0.01 and 0.001 mol/lit). The activity of these zeolites was investigated in a Diels-Alder reaction of cyclopentadiene and maleic anhydride, anthracene and maleic anhydride. The yield ofthese reactions increased in order of (NaY<Fe2+Y<Fe3+Y<MnY<CuY≈NiY<CoY≈CrY<ZnY) for both methods. The aqueous solution ion-exchanged zeolites showed higher activity in comparison to solid state exchange. About 65-70% yield was observed for the Diels-Alder reaction with ZnY Zeolite. Endo-selectivity was observed for these reactions. The best concentration for aqueous solution ion exchange catalyst is 0.1 mol/lit. Hence, the best concentration for microwave solid state is 0.01 mol/lit.

The danger of solid pollution is not less than gas pollution, therefore in this research we used an artificial portable breathing system with cellulose mask during the June and July of 2004 for three consecutive weeks, every day from 8 to 10 and 17 to 19, sampling was done in high traffic working days and in high traffic locations of Tehran Azady square. The suspended solid particles which were conducted in breathing system as dusty, were collected on the mask. Samples weight differences were inconsiderable. Six samples averagely (two samples per a week), were chosen for Electromicroscope Study. Investigations on data taking by SEM indicate the observed solid pollution are consisted on: very tiny and soft Hydrocarbons (soot) that their serried particles diameter reaches 10 micron, clay particles in sizes less than 60 micron in form of tiny sheets of rubber particles as pulverized particles in sizes less than 120 micron and Azbest as needle-like particles in sizes less than 100 micron. Main subject in the research is the study of air dusty particles as Electromicroscope in Tehran city in order to recognize and analyze the kind of suspended particles.

The complexation of molybdenum (VI) with nitrilotriacetic accid (NTA) and ethylenediaminetetraacetic acid (EDTA) have been studied using potentiometric and spectrophotometric techniques. The temperature was kept constant at 25°C and the ionic strength was (0.1, 0.3 and 0.5) mol dm-3 in NaClO4. The composition of the complexes were determined by the continuous variations method. Molybdenum (VI) forms a 1:1 complex with NTA of type (MoO3L3-) and a 2:1 complex with EDTA of the type [(MoO3)2 L]4- where L3- and L4- represent the fully dissociated NTA and EDTA anion at the specified pH. The protonation constants of the ligands (using the potentiometric technique) were determined at 25°C and at different ionic strengths. In both complex formation reactions the dependence of the protonation and stability constants on ionic strength was evaluated using a simple Debye-Huckel type equation. Ultimately, the patterns of the ionic strength effect on the stability constants of two complenes are stadied.

The volatile constituents of the aerial parts of Thymus daenensis Celak. growing wild in Iran have been examined by GC-FID and GC-MS. Altogether, 29 compounds were identified. The oil of Th. daenensis consisted mainly of α-terpineol (24.4%), linalool (14.2%), thymol (10.7%), p-cymene (6.8%), borneol (6.5%) and geranyl acetate (4.0%).  

Excess use of raw cabbage by human and animals effected the activity of the thyroid gland and it is a factor in development of goiter. Manganese (IV) (Mn+4) and thiocyanate (SCN-) is believed to be the cause of the illness amount of manganese and thiocyanate were determined in three kind of cabbage (white, turnip and cauliflower) the ratio of thiocyanate to manganese was found to be 2 in the different cabbages. The structure of the molecule responsible for the goiter development is proposed to be a bridged oxomanganese (IV) with two thiocyanate ligands.

A simple, novel and sensitive spectrophotometric method was described for simultaneous determination of uranium and thorium. The method is based on the complex formation of uranium and thorium with Arsenazo III at pH 3.0. All factors affecting on the sensitivity were optimized and the linear dynamic range for determination of uranium and thorium found. The simultaneous determination of uranium and thorium mixtures by using spectrophotometric methods is a difficult problem, due to spectral interferences. By multivariate calibration methods such as partial least squares (PLS), it is possible to obtain a model adjusted to the concentration values of the mixtures used in the calibration range. Genetic algorithm (GA) is a suitable method for selecting wavelengths for PLS calibration of mixtures with almost identical spectra without loss of prediction capacity using spectrophotometric. In this study, the calibration modelis based on absorption spectra in the 600-760 nm range for 25 different mixtures of uranium and thorium. Calibration matrices were containing 0.10-21.00 and 0.25-18.50 µgmrl-1 of uranium and thorium, respectively. The RMSEP for uranium and thorium with GA and without GA were 0.4340, 0.4580 and 1.5710, 1.0775, respectively. This procedure allows the simultaneous determination of uranium and thorium in synthetic and real matrix samples good reliability of the determination.