Copper(II)-catalysed addition of O-H bonds to norbornene

Cu(OTf)2 is an inexpensive, air- and moisture-stable catalyst for the O-H addition of aliphatic and aromatic acids and alcohols to norbornene.     

Oscillometric titration of inorganic halides with mercury(II) acetate

Summary The difference between the relative ion mobility of the acetate and halide ions, and the well known slight dissociation of the mercury halides can be used for the titrimetric determination of the inorganic chlorides, bromides and iodides with oscillometric determination of the end-point. Errors in the determination of various halogenides were between 0,2 and 1,4%.

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Oscillometrische Titration von anorganischen Halogeniden mit Quecksilber(II)-acetat

Zusammenfassung Der Unterschied zwischen der relativen Ionenbeweglichkeit der Acetat- und Halogenidionen und die bekannte geringe Dissoziation der Quecksilberhalogenide wurde zur volumetrischen Bestimmung von anorganischen Chloriden, Bromiden und Jodiden mit oscillometrischer Endpunktsanzeige verwendet. Die Fehler bei der Bestimmung verschiedener Halogenide lagen zwischen 0,2 und 1,4%.

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Communicated at the 2nd Conference on Applied physical Chemistry in Veszprém on August 2–5, 1971.     

Chloroacetonylation of CC double bonds promoted by manganese(III) acetate

The addition of acetylacetone to alkenes was performed using Mn(OAc)₃·2H₂O in the presence of HCl. The intermediate formed was trapped by chloride. Removal of one of the acetyl groups with ammonia under very mild conditions provided compounds derived from chloroacetonylation of the double bonds.     

Study of the interaction of Lewis bases with mercury(II) chloride and mercury(II) acetate by mercury-199 NMR

The mercury-199 NMR spectra of mercury(II) chloride and mercury(II) acetate in the presence of amines and sulfides in DMSO were recorded. The structure of the coordination compounds is discussed.     

Enhancing the sensitivity of spectrophotometric determination of formic acid with mercury(II) acetate

A precise spectrophotometric method was developed for determination of formic acid. The method surpasses in sensitivity the method based on proper UV absorption of formic acid.     

Theoretical study of azide anion addition to nonpolar and polar double and triple bonds

Transition structures for the 1,3-polar addition of azide anion to hydrogen cyanide, formaldimine, nitrogen, cis- andtrans -diazene, ethylene and acetylene were obtained at the MP2/6-31+G^* theoretical model. The additions can be divided into two groups: addition to a triple bond, giving rise to an aromatic heterocyclic product, and addition to a double bond, forming a non-aromatic product. All transition structures correspond to a concerted mechanism for the polar cycloaddition. Symmetrical dienophiles, apart from cis-diazene, give rise to synchronous transition structures. The anomaly is explained in terms of strong n-n repulsion of the reactants in the transition structure. The reactivity of the compounds can be rationalized in terms of the bond orders of the newly forming bonds, from the frontier orbital energy differences and from the charge transfer from the azide anion to the dienophile. The quantitative correlation of the reactivity has been judged on the basis of the activation energies of the reactions calculated at MP2/6-31+G^* and MP3/6-31+G^*. It is predicted that the addition of azide to nitrogen is the slowest and that the additions to hydrogen cyanide and acetylene have the lowest barriers, in agreement with literature data.     

Oxidation of (E,E,Z)-1,5,9-cyclododecatriene catalysed by palladium(II) acetate in the presence of copper(II) acetate and air: A kinetic study

The oxidation of (E,E,Z)-1,5,9-cyclododecatriene catalysed by Pd(OAc)₂/Cu(OAc)₂ was studied in methyl alcohol solutions at 2.5 MPa air pressure and temperature range of 358 to 383 K. The selectivity of ketones and ethers at conversion of cyclododecatriene up to 32.7% ranged within 87.5–96.0%. The reaction network and kinetic equations proposed suggested a significant inhibition effect of the ketones and ethers and gave the best agreement with the experimental data.     

Oxidation of cobalt(II) aminopolycarboxylate complexes by peroxomonophosphoric acid in acetate buffers. A kinetic study

Summary The kinetics of oxidation of the Co^II complexes [Co(edta)]^2– and [Co(hedta)]^– [H₄edta=ethylenediamine tetraacetic acid and H₃hedta=N-(2-hydroxyethyl)ethylenediamineN, N, N triacetic acid] by peroxomonophosphoric acid (PMPA) in acetate buffer were investigated spectrophotometrically. The reactions exhibit first order behaviour in each reactant and are markedly in hibited by H⁺. A plausible mechanism consistent with the observed results is proposed.     

Oxidative addition of mercury(II)cyanide toβ-diketonatobis-(triphenylphosphite)rhodium(I) complexes

Summary The kinetics of the oxidative addition of Hg(CN)₂ to [Rh(-diketone)(P(OPh)₃)₂] in acetone medium were studied. Various -diketones, with different electronic and steric properties, were used to determine their effect on the rate of the oxidative addition reactions. The structure of the product of the oxidative addition was proposed with the aid of i.r.,¹H–,¹³C– and³¹P n.m.r. spectra. A product in whichcis addition took place with the CN^– and one P(OPh)₃ group in the axial positions of an octahedron were proposed. A second order rate law, electronic and steric factors influencing the reaction rate as well as large negative values for the entropy of activation, supported an associative type of mechanism, which probably proceedsvia a cyclic three-centred transition state.     

Interaction of nitrogen-containing propargyl compounds with CH-acids in the presence of mercury(II) acetate

Regiochemistry of the reaction of nitrogen-containing propargyl compounds with CH-acids in the presence of mercury(II) acetate has been studied. The possibility of alkylation at the substituted carbon atom of the triple bond of the nitrogen-containing propargyl compounds by sodium salts of acetylacetone and acetoacetic ester with the formation of prototropic isomers has been shown.     

The addition of fluorine to perhalogenated compounds containing carbon-nitrogen double bonds

The reaction of elementary fluorine with ten perhalogenated compounds containing carbon-nitrogen double bonds is reported. The reactions were carried out without added catalysts in a static system. With CF₃N=CF₂, (CF₃)₂NCF=NCF₃, SF₅N=CF₂, CF₂=NCl, CF₃CF=NCl and CF₂=NF a simple addition of fluorine to the carbon-nitrogen double bond was observed forming the respective N-fluoroamines in high yield. Two imines, CF₃CF=NF and (CF=NF)₂, were unreactive under the same conditions and reactions of CF₃CF₂CF=NF and (CF₃)₂C=NF were explosive.     

Reduction of mercury(II) by tropical river humic substances (Rio Negro) - A possible process of the mercury cycle in Brazil

The evolution of elemental Hg from its environmental compounds has already been supposed to be an important process within the global mercury cycle. The present study characterizes the abiotic reduction of Hg(II) ions by typical river humic substances (HS) conventionally pre-isolated by the adsorbent XAD 8 from the "Rio Negro" near Manaus, Brazil. For the investigation of this reduction process a special reaction and Hg(0) trapping unit combined with cold-vapor atomic absorption spectrometry (CVAAS) was developed. Preconcentration of traces of mercury(II), if required, was obtained by a home-made FIA system using microcolumns filled with the Hg(II)-selective collector CheliteS(R) (Serva Company). The effect of environmentally relevant parameters such as the pH value, the Hg(II)/HS ratio and the HS concentration on the Hg(II) reduction process was studied as a function of the time. The Hg(0) production was highest at pH 8.0 and in the case of decreasing HS amounts (0.5 mg) when about 65% of initially 1.0 mug Hg(II) was reduced within 50 h. Moreover, the reduction efficiency of HS towards Hg(II) strongly depended on the HS concentration but hardly on the Hg(II)/HS ratio. The reduction kinetics followed a relatively slow two-step first-order mechanism with formal rate constants of about 0.1 and 0.02 h(-1), respectively. Based on these findings the possible relevance of the abiotic evolution of mercury in humic-rich aquatic environments is considered.     

A molecular orbital study of trans-polyenes to 18 double bonds

Calculations involving molecular orbitals have appeared in the chemical literature over the past few years, but all have used smalltrans-polyenes. We now report extended Huckel molecular orbital calculations ontrans-polyenes of up to 18 double bonds (36 carbons and 38 hydrogen atoms). Information obtained from these calculations include total energies, bond gaps, and net charges on each atom. Also found is that the band gap approaches 1.41 eV as the number of double bonds approaches infinity. This value is quite close to reported experimental values. Data are also presented for polyenes assuming equal C-C bond lengths.     

Application of variable-temperature kinetic experiments to oxidative addition reactions of dimethylplatinum(II) complexes with alkyl halides

Rate constants and activation parameters of oxidative addition reactions of [PtMe₂(2,2′-bipyridine)] with EtI and [Pt(p-MeC₆H₄)₂ (2,2′-bipyridine)] with MeI in solvents acetone and benzene have been obtained very easily and with good accuracy from variable-temperature spectrophotometric kinetic data using a method based on nonisothermal analysis. The results are compared with those obtained by the traditional isothermal method. It is shown that there are significant advantages to measuring the reaction rates under variable-temperature kinetic conditions, as compared to the constant-temperature kinetic method.     

Oxidative addition of methyl iodide to a new type of binuclear platinum(II) complex: a kinetic study

A new organodiplatinum(II) complex cis,cis-[Me2Pt(mu-NN)(mu-dppm)PtMe2] (1), in which NN = phthalazine and dppm = bis(diphenylphosphino)methane, is synthesized by the reaction of cis,cis-[Me2Pt(mu-SMe2)(mu-dppm)PtMe2] with 1 equiv of NN. Complex 1 has a 5d(pi)(Pt) --> pi(imine) metal-to-ligand charge-transfer band in the visible region, which was used to easily follow the kinetics of its reaction with MeI. Meanwhile, the complex contains a robust bridging dppm ligand that holds the binuclear integrity during the reaction. A double MeI oxidative addition was observed, as shown by spectrophotometry and confirmed by a low-temperature 31P NMR study. The classical S(N)2 mechanism was suggested for both steps, and the involved intermediates were suggested. Consistent with the proposed mechanism, the rates of the reactions at different temperatures were slower in benzene than in acetone and large negative deltaS values were found in each step. However, some abnormalities were observed in the related rate constants and deltaS values, which were demonstrated to be due to the associative involvement of the polar acetone molecules in the reactions. The rates are almost 6 times slower in the second step as compared to the first step because of the electronic effects transmitted through the ligands and the steric effects.