A NEW ONE-STEP REDUCTIVE N-ALKYLATION OF AMINO ACIDS AND THEIR ESTERS

The reductive alkylation of amine with carbonyl compounds usingsodium hydrogen telluride has been investigated in recent years.Application of this method to the synthesis of N-alkyl derivativesof biologically important amino acids and their esters is described.     

On the biological importance of the hydrogen bond breaking potency of fluorocarbons

Fluorocarbons containing higher halogens have the potency of breaking certain hydrogen bonds in solutions. The relative strength of this potency varies in the series F < Cl < Br < I and the presence of hydrogen atoms in the fluorocarbon increases it. There is a striking parallelism between the hydrogen bond breaking and the anaesthetic potency of these molecules. It is suggested that the breaking of hydrogen bonds is an important step in the mechanism of anaesthesia.     

Oxidation of organophosphorus compounds—IV : Kinetics and mechanism of the oxidation of diarylphosphine oxides by t-butyl hydroperoxide,hydrogen peroxide and p-nitroperoxybenzoic acid in alkaline media

The influence of OH⁻ concentration, in the solvent medium dioxane-water 40:60 at 25·0, on the oxidation rates of diphenylphosphine oxide (DPPO) by t-BuOOH, H₂O₂ and p-nitroperoxybenzoic acid, and of bis-p-tolylphosphine oxide by t-BuOOH has been investigated. For the oxidation of the phosphorus substrates by the hydroperoxides above, the rate law found (R = k₂″[Ar₂PHO] [ROO⁻]) differs from the rate law confirmed to hold for the oxidation of DPPO by peroxyacids in alkaline media, i.e.: R = (k₂″ + k₃[OH−])[Ar₂PHO] [RCO₃⁻]. This is interpreted on the basis of one common reaction mechanism involving formation of an intermediate of similar structure, wherein a change in the rate controlling step is likely to occur on passing from p-O₂N·C₆H₄CO₃⁻ to t-BuOO⁻. In the same solvent medium, pK_a′ values for t-BuOOH and H₂O₂ have been estimated.     

Intercalation of α,ω-alkyldiamines in layered α-zirconium phosphate and the inclusion behaviour of some of the intercalates obtained

The paper reports a study on the intercalation mechanism of NH₂(CH₂) _n NH₂ (withn=2, 4, 6, 8, 10) diamines in layered Zr(HOPO₃)₂·H₂O, performed by titrating the host with aqueous solutions of amines at 80°C. The intercalation reactions occur stepwise according to the ‘moving boundary’ model, with the formation of a number of intermediate intercalation compounds of formula Zr(HOPO₃)₂·xNH₂(CH₂) _n NH₂ (0<x<1) before obtaining the fully intercalated ones (x=1). For each diamine the batch titration curve and a diagram of the phases involved in the interaclation reaction are reported. Twenty-two intercalation compounds have been isolated and characterized by their composition, XRD patterns and thermal behaviour, and information on the disposition of the guests within the interlayer region have been derived. At full intercalation the diamines form a monolayer of extended molecules with their axis inclined at 58° to the plane of the sheet. The terminal amino groups are protonated by the —POH groups of the host, thus each diamine binds adjacent layers and, in a sense, transforms a layered structure into a framework structure that may have an accessible or potentially accessible porosity. The intercalation compound Zr(HOPO₃)₂·0.5NH₂(CH₂)₈NH₂ is indeed able to include polar molecules such as water and short chain alkanols.     

Kinetic and catalytic aspects of dimethylterephtalate transesterification also through the use of model molecules

Kinetic and catalytic aspects of DMT transesterification reaction, key step in the industrial production of polyethylenterephtalate (PET), have been deepened also through the use of model molecules such as CH₃COO–Ph–X. These molecules give the same reactions with ethylene glycol occurring in the DMT transesterification too. The use of model molecules in the study of this reaction seems therefore to be promising in perspective. As we observed, however, the nature of the para-substituent X has a very strong influence on the reaction rate, when salts of bivalent metals such as Zn, Cd, Co, Mg, Mn, are used as catalysts, while this influence is much smaller when a tetravalent metal, as Ti, is used. This fact suggests that the transesterification mechanism operating in the two cases is different and this suggestion has been confirmed by applying Hammett's approach to the available kinetic data. Experimental kinetic runs were all performed at 193°C, by withdrawing small samples of the reaction mixture at different reaction times. These samples were gaschromatographically analyzed. We found volcano shaped curves of the reaction rates as a function of the metal ion acidities and we obtained different trends with a maximum of activity shifted from a metal to another for different substrates. A comparison of the kinetic results obtained, respectively, with the model molecules and DMT will be reported too.     

Transition Metal Complexes with Bidentate Ligands Spanning trans-Positions. VIII. The reactions of the nucleophile trans-[RuCl(NO)(1)] (1 = 2,11-bis(diphenylphosphinomethyl)benzo[c]-phenanthrene) with carbon monoxide and the phosphite ligand (2) (2 = 1-ethyl-3,5,8-trioxa-4-phosphabicyclo (2.2.2)octane)

The preparation of the nucleophile trans-[RuCl(NO)( 1 )], where 1 is the bidentate ligand Ph₂PCH₂C₁₈CH₂PPh₂, and of the five-coordinate species [RuCl(CO)(NO)( 1 )], [RuCl(CO)(NO)(Ph₂PCH₂Ph)₂] and [RuCl(NO)( 2 )( 1 )] are reported. The crystal structure of [RuCl(CO)(NO)( 1 )] shows that the coordination around the metal atom is distorted trigonal bipyramidal with the phosphorus atoms in axial positions. The Ru? N? O bond angle is 142.8°. ¹H- and ³¹P-NMR. and \documentclass{article}\pagestyle{empty}\begin{document}$ \tilde \nu $\end{document}_NO IR.-data for the above complexes are reported and related to the coordination geometry.     

Automorphisms of (B)-geometries

(B)-Geometries are incidence structures arising from permutation sets. The present paper studies the automorphism groups of (B)-Geometries. In certain cases these automorphisms yield examples of inversive planes and of subplanes which are embedded in Minkowski planes (chapter 2). In chapter 3 we describe the automorphism groups of the (B)-Geometries arising from the groups PL(2, pⁿ) and AL(1, pⁿ) in their natural representations on the points of the projective and affine line.Dedicated to Prof.Dr. Walter Benz on his 60th birthdayWork done within the activity of G.N.S.A.G.A. of C.N.R. and supported by the 40% grants of M.U.R.S.T.