Étude de la dissipation d'énergie dans la fission de 234u à l'aide de la réaction 233U(d,pf)

The energy balance in the fission of ²³⁴U has been investigated on the basis of experimental results from the ²³³U(d, pf) reaction. Taking into account the neutron evaporation we have deduced the total kinetic energy and excitation energy distributions of the primary fragments as functions of the excitation energy of the fissioning nucleus. The neutron evaporation temperatures have been adjusted so as to reproduce the average value and width of the measured kinetic energy distributions for each fragmentation. Excitation energy distributions of the fragments have been deduced. The data are discussed in the framework of the liquid-drop model with shell corrections. Evidence for energy dissipation in the fission of ²³⁴U, involving drastic changes in the scission configuration, is shown for some fragmentation modes.     

Easy preparation of the tris(2-fluoro-6-pyridylmethyl)amine ligand and instantaneous reaction of the corresponding dichloroferrous complex with molecular dioxygen: new access to dinuclear species

The tris(2-fluoro-6-pyridylmethyl)amine ligand, F3TPA, can easily be prepared by reaction of 2-fluoro-6-bromomethylpyridine with NH4Cl in the presence of NaOH. Complexation to FeCl2 affords the high-spin F3TPAFe(II)Cl2 complex, the X-ray structure of which is reported. The three fluorine substituents provide enough steric hindrance to force the tripod to coordinate in the tridentate mode, affording a trigonal bipyramidal iron center. This complex is thermally stable, and it reacts instantaneously with molecular dioxygen to afford the unsymmetrical micro-oxo dimer F3TPAFe(III)ClOFe(III)Cl3 as the major product, together with small amounts of the mixed salt [F3TPAFe(II)Cl]2, [Fe(III)2OCl6]. These two complexes have been isolated and characterized by X-ray diffraction analysis. A mechanism by which they are obtained is suggested and seems to parallel the well-known process of autoxidation of ferrous porphyrins.     

Li<Subscript>2</Subscript>HPO<Subscript>3</Subscript>, H<Subscript>2</Subscript>O: Crystal Structure and IR Spectrum

Abstract  

Crystal structure of Li₂HPO₃,H₂O was determined by single-crystal X-Ray diffraction analysis at 173(2) K. It crystallizes in the monoclinic system (P2_1/c) with the parameters: a = 5.0322(9) ?, b = 8.9795(17) ?, c = 17.088(4) ?, β = 92.672(16)° and Z = 8. The structure was refined to R = 0.0237 and ωR = 0.0650 for 1449 reflexions. The framework of Li₂HPO₃, H₂O can be described as layers perpendicular to the crystallographic c axis. The structure contains two types of Li-tetrahedrons. In one kind each O atom belongs to one HPO₃ group, while in the second kind one apex is an O from water. A network of hydrogen bonds interactions insures the connection between the layers.     

Crystal Structure and IR Study of (C<Subscript>6</Subscript>H<Subscript>5</Subscript>NH<Subscript>3</Subscript>)[ZnCl(HPO<Subscript>3</Subscript>)]

Abstract  

A new hybrid phosphate, (C₆H₅NH₃)[ZnCl(HPO₃)], has been synthesized and its structure characterized from single-crystal X-ray diffraction. The title compound crystallizes in the orthorhombic space group Pbca (n. 61) with the unit-cell parameters: a = 9.8635(2) ?, b = 9.4516(10) ?, c = 22.2430(4) ?, Z = 8 and V = 2,073.62(6) ?³. The final R factors were R/ωR = 0.0361/0.0924. Its framework might be described as a layered structure with two (010)-parallel cationic and anionic layers. The IR spectrum of this phase shows characteristic bands of phosphite and anilinium groups.     

Unprecedented incorporation of α-emitter radioisotope 213Bi into porphyrin chelates with reference to a daughter isotope mediated assistance mechanism

For the first time, α-emitter radioisotope (213)Bi has been incorporated into porphyrin chelates, with rates matching with the short period of the radionuclide. An in situ transmetalation mechanism involving the daughter isotope (209)Pb is expected to boost the (213)Bi radiolabeling process.     

Antioxidant activity,phytochemical screening,and total phenolic content of extracts from three genders of carob tree barks growing in Morocco

We evaluated the in vitro antioxidant property and phytochemical constituents of the crude ethyl acetate and methanol extract of the three genders of carob tree barks (spontaneous male, spontaneous female, and grafted female). The scavenging activity on DPPH (1,1-diphenyl-2-picrylhydrazyl) was determined, as well as the phenolic contents (Folin–Ciocalteu method) of both the extracts. The highest antioxidant activity and the higher amounts of total phenols were shown in methanol crude bark extract for the three genders. Variety significantly affected the phenol content and the antioxidant activity, with the spontaneous male variety globally showed a higher polyphenol concentration and antioxidant activity than the grafted female and spontaneous female.     

New route to 15-hydroxydehydroabietic acid derivatives: application to the first synthesis of some bioactive abietane and nor-abietane type terpenoids

A new route to 15-hydroxydehydroabietic acid derivatives from abietic acid (11), via abieta-8,13(15)-dien-18-oic acid (12), is reported. Utilizing this, the first synthesis of bioactive terpenes 3, 6, 9 and 10, as well as natural diol 4 and lactones 7-8 was achieved.     

Isolation and X-ray crystal structure of tetrahydroisoquinoline alkaloids from Calycotome villosa Subsp. intermedias

Two tetrahydroisoquinoline alkaloids were extracted from the alkaloid fraction of a methanol extract of the seeds of Calycotome Villosa Subsp. intermedia. Their structures were established as (R)-1-hydroxymethyl-7-8-dimethoxy-1,2,3,4-tetrahydro- isoquinoline (1) and (S)-7-hydroxymethyl-2-3-dimethoxy-7,8,9,10-tetrahydroisoquinoline chloride (2) by spectroscopic techniques and X-ray diffraction analysis.