Iranian Journal of Chemistry and Chemical Engineering
Volume:18 Issue: 2, Nov-Dec 1999

A spectrophotometric method is used to determine the acidity cons-tants of some derivatives of 9, 10-anthraquinone in binary methanol-water mix-tures at 25ـC. There is a linear inverse relationship between pKa of all acids andthe mole fraction of methanol in the mixed solvent. The influence of substituentsin the molecular structure on the ionization constants is discussed.

The epoxidation of olefins with tetra n-butylammonium periodate,n-Bu4NIO4, is catalyzed by six different tetrakis (4-substituted phenyl) porphyrin-atomanganese(III) acetate, Mn(T4-XPP)OAc, complexes in the presence of imida-zole as an axial ligand with low to high yields and complete selectivity at roomtemperature. While the electronic effects of the highly electron-withdrawing NO2substituents are clearly reflected in the reduction of epoxidation yields, othersubstituents, i.e MeO, Me, Cl, and Br, do not significantly modify epoxide yieldsrelative to Mn(TPP)OAc and give very similar results.

Vanadium is quantitatively retained on 2-nitroso-1-naphthol-4-sulfonic acid tetradecyldimethylbenzylammonium chloride onto microcrystallinenaphthalene in the pH range of 3.0-4.0 from a large volume of aqueous solutionsof various alloys and synthetic samples. After filtration, the solid mass consistingof the vanadium complex and naphthalene was dissolved with 5.0 mL of dimethyl-formamide and the metal was determined by scond derivative spectrophotometry.The detection limit is 40 ppb (signal to noise ratio= 2) and the calibration curveis linear over the concentration range of 0.08-20 ppm in dimethylformamide solu-tion by measuring the distance d2A/dl2 between l1 (575 nm) and l2 (510 nm) witha correlation coefficient of 0.9995 and relative standard deviation of ×0.98%.The effect of pH, volume of aqueous phase and interference of a large number ofmetal ions on the determination of vanadium was studied and the developedmethod is found to be highly selective and sensitive.

The complexation reactions between N, Nإ-3, 6-dioxa-1, 8-octanebis (salicyl-aldimine) [saldioxen (I)] and Mn (II), Co (II), Ni (II), Cu (II), Zn (II), Cd (II) and Hg (II) were studied spectrophotometrically in methanol solution at 25ـC. The stoichiometry ofthe complexes were obtained as 2:1 and 1:1 saldioxen-metal ion using mole ratiomethod. The formation constants of the complexes were determined, and found tofollow the Irving-Williams, rule for the cations of the first transition series. IRspectroscopy and other evidence indicated that, in 2:1 complexes, the coordinationtakes place through the azomethin nitrogen atoms only, whereas in 1:1 complexes, metal ion coordinated with ligand through two azomethin groups and the phenolicoxygen atoms.

Conformations and electronic properties of a series of imidazo-benzodiazepines are investigated by AM1 semi-empirical quantum mechanicsmethod. It is shown that substitution of Cl in position 7 instead of 8, changes thegeometry of the seven membered lactam ring; this may put the N5 nitrogen in abetter position to act as a hydrogen bond acceptor, and the phenyl ring in position6 is probably more adapted for hydrphobic pocket of the receptor binding site.

Effects of ATP and Mg+2 concentrations on bioluminescence reactionof luciferase (Photinus pyralis) were investigated by home-made luminometer. TheMichaelis constants of the enzyme for ATP and Mg+2 obtained from the Lineweaver-Burk graph, were 61.9 mM × 3.3 mM and 251.6 mM × 39.0 mM respectively. Optimumconcentration of Mg+2 for maximum luminescence was 0.004 M.

In an environmentally benign solventless system، alcohols are rapidlyoxidized to carbonyl compounds using hexamethylenetetramine-bromine on wetalumina under microwave irradiation.

New macrocyclic polyether-diester ligands (3-5) containing the 4H-pyran-4-one subcyclic unit have been prepared by treating various glycols withdimethyl chelidonate (10). In the reaction of compound 10 with ethylene glycoland diethylene glycol، two noncyclic diester and tetraester (6-9) were produced ineach case. The new macrocyclic ligand 4 formed stable complexes with benzyl-ammonium perchlorate and potassium thiocyanate salts. The starting compound10 was prepared through a novel method.

The kinetics and mechanisms of the substitution reactions of trans-[Co (en) 2CNCl]+ with unidentate anions، NO2-، CN-، I-، N3-، Br-، and SCN- in 60%v/v DMF-H2O binary solvent at 40. 0×0. 2ـC were studied spectrophotometrically. AnId mechanism was assigned for the replacement of chlorine by NO2-، CN-، and I-،an Ia one for the entry of N3- and SCN-، and a D mechanism for Br- entry. Comparing the interchange rate constants، ki، values has led to the following trend ofreactivity of the anions toward the given substrate: NO2- > N3- > Br- > CN- > H2O > I- > SCN- The replacement of chlorine by the anions proceeded with a complete retention ofconfiguration.

Phthalocyanine complexes of Cu، Co، Ni، Fe، Zn، Pd، Pt and Ruhave been synthesized from reaction between phthalonitrile and proper metal saltsupon exposure to microwave irradiation under solvent-free conditions and consi-derably reduced reaction times.

The water-distilled essential oil from dried aerial parts of Achilleatenuifolia Lam. was analysed by GC and GC/MS. 48 Components were characteri-zed representing 88% of the total oil. Camphor (18%)، 1،8-cineole + limonene (9%) and spathulenol (7%) were the major constituents of the oil obtained in ayield of 0. 23%.