Hydride Content Research Articles

Metallographic studies of fatigue in 20% cold-worked zircaloy-2 containing zirconium hydride

The fatigue behaviour of unhydrided and hydrided 20% cold-worked zircaloy-2 reactor pressure-vessel tubing has been studied for fluctuating tension at room-temperature and 300 °C and for reversed torsion at room-temperature. At room-temperature, high concentrations of zirconium hydride markedly reduce the critical crack length. This effect is attributed to a lowering of the fracture toughness, since hydrides fracture in the path of crack propagation and promote matrix cleavage. At 300 °C, hydride particles constrained by the matrix are plastically deformed without fracturing; the toughness is probably unaffected by the presence of hydride.

Evidence for Hydrogen Abstraction by Classical Radicals in the Norbornenyl-Nortricyclyl System

Studies of product compositions and deuterium-label rearrangements at various concentrations of tri-n-butyltin hydride in the reductions of exo-and endo-5-bromonorbornene and 2-bromonortricyclcne to mixtures of norbornene and nortricyclene lead to three main conclusions: (i) at least two radical intermediates contribute to product formation; (ii) each intermediate yields predominantly (80% or more) one product; and (iii) nortricyclene is predominantly derived from a symmetrical intermediate. This constitutes strong evidence for hydrogen abstraction by classical (i.e., single-product) norbornenyl and nortricyclyl radicals. It is argued that the norbornenyl-nortricyclyl system is exceptionally well suited for the generation of a nonclassical (dual-product) radical; hence, the existence of a nonclassical radical in any other system is rather unlikely.

Kinetics of the reaction of metal-alkyl compounds with alkenes III. Diisobutylaluminium hydride

The addition of dissobutylaluminium hydride to 1-butene is investigated and the rate found to exhibit half order in aluminium hydride concentration. A mechanism is given in which the monomeric form of the aluminium hydride is active in the addition reaction. It has been shown that the addition of aluminium alkyls to n-alkenes is limited by the dissociation of the dimer 1,2, i.e.: Al 2Et 6 ←→ 2 AlEt 3 (1) as addition proceeds through the monomer, i.e.: AlEt 3CH 2=CHR → Et 2AlCH 2CH(Et)R (20 Under the conditions of the reaction the β-branched alkyl group is eliminated and in the presence of excess n-alkene an n-alkylaluminium compound is produced. An aluminium hydride intermediate rather than direct group displacement may be involved in this reaction, i.e.: Et 2AlCH 2CH(Et)R → Et 2AlH+CH=C(Et)R (3) Et 2AlH+CH 2=CHR → Et 2AlCH 2CH 2R (4) This overall reaction scheme was substantiated by a study of the reaction products of triethylaluminium and n-1-octene to high conversions. These were 2-ethyl-1-octene-, hexadecene; n-octyl-, 2-ethyloctyl- and hexadecylaluminium compounds. The present paper considers the evidence for the displacement reaction proceeding via a hydride intermediate in the light of the reactivity of diisobytylaluminium hydride to n-1-butene addition, and is compared with the addition reaction with triethylaluminium

Colorimetric Determination of Organotin Hydrides with Isatin or Ninhydrin

AbstractTwo new colorimetric methods were developed for the quantitative determination of organotin hydrides. They are based on the reduction of the carbonyl groups of isatin or ninhydrin by organotin hydrides. In the first case colourless dioxindole is formed, and the lowering in the optical density of an isatin solution is taken as the basis for the determination. In the second case the coloured salt of 2‐hydroxyindanedione is formed. The reactions are sensitive and it is possible to determine concentrations of organotin hydride to about 10−4 mole/1.

Colorimetric determination of boron hydrides by means of phosphomolybdic acid.

A procedure is described for the colorimetric determination of boron hydrides by means of phosphomolybdic acid. Phosphomolybdic acid reacts with various boron hydrides or derivatives thereof to form blue solutions. The intensity of the color produced is a linear function of the concentration of boron hydride involved, and it can be used for the microanalysis of the compound. (C.H.)