摘要:

This paper considers parent reformation in molecules in which the central atom recoils at high energy, following neutron capture. It is postulated that parent reformation following diffusion of the recoil atom back to the initial site can be successful only if the recoiling atom does not cause serious damage to the ligand structure. By using the Bohr screened potential, the probability of ligand-structure damage has been calculated and found to be negligible. The results are compared with experimental data. Although the comparison is not straightforward, the widespread lack of correspondence leads to the conclusion that back diffusion as postulated plays a minor role, if any, in parent reformation in the cases studied. An important conclusion reached from these calculations is that the probability of such damage is not very sensitive to uncertainties in the initial recoil energy.

ISSN:0008-4042    

DOI:10.1139/v67-292

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

The kinetics of the propagation reaction in the polymerization of isoprene initiated by butyllithium in tetrahydrofuran solution have been studied. The kinetic behavior has indicated that the reactive species involves both the polyisoprenyllithium ion-pair and the free poly-isoprenyl carbanion. The conductances of solutions of polyisoprenyllithium have been measured and the ionic dissociation constant derived. From these the free ion rate constant has been evaluated. It has also been shown that the free ion reaction may be suppressed by the common ion effect when the salt lithium tetraphenylboron is added. The rate constants for the ion-pair and free ion are 0.20 M−1 s−1and 2.8 × 103 M−l s−1respectively; the ionic dissociation constant is 5.0 × 10−10. Nuclear magnetic resonance determinations of the structures of the polymers formed primarily by the free carbanion, and by the ion-pair only, show that the lithium ion has only a small directing effect.

ISSN:0008-4042    

DOI:10.1139/v67-293

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

Diffusion of one rare gas into an equimolar mixture of two other rare gases has been followed using krypton-85 or xenon-133 tracer. The systems behave as pseudo-binary diffusion systems. A kinetic theory equation, valid for diffusion of a trace in a multicomponent mixture, is not a good approximation for diffusion of a major component.

ISSN:0008-4042    

DOI:10.1139/v67-294

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

Proton magnetic resonance spectra of succinic anhydride, maleic anhydride, and the N-ethyl- or N-(p-chlorophenyl)-imides have been investigated in various media. In benzene solution, a specific interaction between the π-electron cloud of the solvent and the moiety of the protons alpha to the carbonyl groups is suggested. The strength of the interaction is considered to be in the order of (i) maleic anhydride, (ii) succinic anhydride, and (iii) the N-substituted imides. The interaction may be due to both the large electron affinity and the polarization of the carbonyl group. The low-field shifts in strongly polar solvents, such as acetone or dimethyl sulfoxide, are ascribed to the preferential associations of the lone-pair electrons of polar solvents to the electron-deficient sites of solute molecules. In some cases, however, the solvent effects on the chemical shifts are opposite to those expected from the donor properties of the solvents. An explanation may be available from the anisotropic magnetic susceptibilities of the polar groups of the solvent molecules.

ISSN:0008-4042    

DOI:10.1139/v67-295

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

The electrolysis of α-bromovaleric, α-bromocaproic, α-bromodiethylacetic, and α-bromoisobutyric acids in both methanol and water has been studied. This represents the first detailed study of the behavior of α-halocarboxylic acids during Kolbe electrolysis.Under the experimental conditions, Kolbe dimer of the α-bromoacid is not produced, even in small amounts, in either solvent. In methanol, hydrogen ester and bromoester were the major electrolysis products. In water, straight-chain acids gave alkyl halide, 1,1-dibromoalkane, and Kolbe dimer of hydrogen acid, whereas branched-chain acids gave ketone and other products from bromination of the ketone. In both solvents, considerable free bromine was produced.

ISSN:0008-4042    

DOI:10.1139/v67-296

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

Reaction of O(3P) atoms with ethanol in the vapor phase has been studied at room temperature. The principal initial reaction products are water, acetaldehyde, and 2,3-butanediol. The data are consistent with abstraction of an α-hydrogen from ethanol as the primary step in the reaction. Ethanol is found to react with O(3P) atoms about 3.5 times less rapidly than acetaldehyde. The approximate absolute value of the rate constant of the ethanol reaction at 25 °C is 6.2 × 1010 cm3 mole−1s−1.As a corollary to the investigation of the reaction of oxygen atoms with ethanol, a brief study has been made of the mercury Hg 6(3P1) photosensitized decomposition of ethanol at room temperature.

ISSN:0008-4042    

DOI:10.1139/v67-297

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

The independent formation cross sections of139Ba,139Ce,141Ce, and143Ce, and the cumulative formation cross sections of139Cs,141Ba, and143La, produced from the fission of natural uranium by protons of energies 20–85 MeV, have been measured radiochemically. The proton energies at which the excitation functions reach their maxima correlate well with the neutron-to-proton ratio of the fission product. Nuclear charge-dispersion curves exhibit, with increasing proton energy, the behavior previously found by other workers, i.e. broadening and a shift of the most probable nuclear charge towards stability.

ISSN:0008-4042    

DOI:10.1139/v67-298

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

The retarding potential difference (r.p.d.) efficiency curves of methane obtained with two different types of mass spectrometers are presented and discussed. It is shown that a Jahn–Teller splitting could explain some of the experimentally observed energy levels. Pre-ionization is shown to occur at 14.4, 16, and 19.5 eV. In particular, the latter value is rediscussed in terms of the second ionization potential of methane. It is concluded that the recent explanation of Ehrhardt and Linder, according to which the 19.5 eV level is a forbidden pre-ionized state, is compatible with our results and that the second ionization potential of methane should be around 24 eV. Ion–molecule reactions are shown to be of small importance around 19.5 eV, contrary to a hypothesis suggested by Sjögren.

ISSN:0008-4042    

DOI:10.1139/v67-299

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

The ionization processes in acetylene under photon, electron, ion, and metastable atom impact, including new results, are critically discussed in relation with the electronic structure of acetylene and with the known spectroscopic information. It is shown that the first ionization potential at 11.409 eV corresponds to a 1 πuelectron removal and that Franck–Condon processes yield an adiabatic ionization potential in this particular case. The new production of ions around 13.25 eV and 14.5–15 eV is due to pre-ionized states probably optically forbidden. From the discussion it is suggested that these might be excited linear σg πu4 πg* or σg πu4 πu* states. The second ionization potential of acetylene, related to the removal of a 3 σgelectron, is shown to be around 16.5 eV.

ISSN:0008-4042    

DOI:10.1139/v67-300

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

Transfer of energy from constituents in active nitrogen to gaseous organometallic compounds leads to dissociation of the organometallic and excitation of CN and (or) metal atom. Organometallic compounds of aluminium, zinc, and boron were used in this investigation. The observed emission lines from metal atoms and highly vibrationally excited CN correspond to an initial energy transfer in excess of 200 kcal/mole. The possible role of N2(5&Sgr;g+) molecules as excitors is discussed in the light of the results obtained.

ISSN:0008-4042    

DOI:10.1139/v67-301

出版商:NRC Research Press    

年代:1967

数据来源: NRC