摘要:

We have determined equilibrium conditions for each reaction in the solid interconversion sequence, in aqueous carbonate solutions near 25 °C. Our data yield the following Gibbs energies of formation from the elements, ΔfG°(298.15 K): plumbonacrite, −5310 ± 31 kJ mol−1; hydrocerussite, −1705 ± 11 kJ mol−1; cerussite, −628.0 ± 3.9 kJ mol−1. Corresponding estimated values of ΔfG°(373 K) are −5120 ± 50, −1643 ± 18, and −612 ± 9 kJ mol−1, respectively. We have demonstrated the existence of a narrow stability field for plumbonacrite, and convenient small-scale preparations of hydrocerussite and plumbonacrite are described. Gibbs energy data for the solids have been combined with selected data for aqueous lead species in a detailed computation of solubility behaviour for this system at 25 °C.

ISSN:0008-4042    

DOI:10.1139/v84-070

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Singlet and triplet benzyl radical pairs have been generated on silica gel by photolysis of a benzyl phenylacetate, a dibenzyl ketone, and a dibenzyl sulfone. The extent of geminate radical recombination has been measured and requires that translational motion of radicals occur on the silica gel surface. This motion was affected by the radical pair multiplicity and the photolysis temperature, but was relatively insensitive to the state of hydration of the silica gel and the presence of coadsorbates. The presence of certain rearranged starting materials, which are not formed in solution, amongst the products from photolysis of both dibenzyl ketone and dibenzyl sulfone on silica gel indicates the restrictions on radical movement on the surface on the shorter timescale of the benzyl–phenylacetyl and benzyl – benzyl sulfonyl radical pairs.

ISSN:0008-4042    

DOI:10.1139/v84-071

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

A chemical correlation is described by which the two adducts resulting from a catalyzed addition oftrans-piperylene to 2-methyl-2-cyclohexenone,7and8, are proven to be stereoisomers. Various reaction conditions for the addition oftrans-piperylene to 2-cyclohexenone are also summarized.

ISSN:0008-4042    

DOI:10.1139/v84-072

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Emissions from excited SO2in its singlet state (1B1, and/or1A2) and triplet state (3B1) have been observed in gas-phase chemiluminescent reactions of ozone with a number of sulphur compounds. The compounds studied are carbon disulphide, thiophene, diallyl sulphide, diallyl disulphide, dimethyl sulphide, dimethyl disulphide, and thiophenol. The reaction pathways responsible for the formation of excited molecules are discussed. The remarkable similarity between the emission spectra of the reactions and the chemiluminescence from the SO + O3reaction confirms that SO is a precursor for the observed chemiluminescence. Disulphides are found to be more chemiluminescent than monosulphides. The absence of chemiluminescence from HCHO* in the reactions of ozone with allyl sulphide and disulphide indicates that the attack of ozone molecule is on the C—S bond in organic sulphides.

ISSN:0008-4042    

DOI:10.1139/v84-073

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

We have shown that radical cations generated by photoinduced electron transfer (ET) in 1,2-diarylethanes, aryl pinacols, and their derivatives undergo fragmentation reactions. In the presence of oxygen oxidative products are obtained. Time-resolved laser flash photolysis and other ancillary techniques have permitted us to define the mechanisms of certain oxidative processes observed.

ISSN:0008-4042    

DOI:10.1139/v84-074

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Thetert-butyldimethylsilyl nitronate derived from 1-nitropropane was condensed with 2,3,4,6-tetra-O-acetyl-β-D-glucopyranosylthiol to yield two geometrically isomeric thiohydroximates; theZ-isomeric form was then converted by conventional procedures into potassium ethylglucosinolate ("glucolepidiin").

ISSN:0008-4042    

DOI:10.1139/v84-075

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

We have developed a new IR-ATR spectroscopic technique for the identification and quantification of fibers collected on PVC filters. This nondestructive method has a detection limit of about 10 μg, involves no sample preparation, and is relatively insensitive to nonserpentine dusts normally associated with the asbestos mining and milling industries.An analysis of the ATR phenomena for a fiber matt indicates that the logarithmic ratio of the reflectivity varies with the surface concentrationCas:whereCsis the concentration for a monolayer of fiber,rthe mean fiber diameter. Thus, the absorption should reach a plateau when a sufficient thickness is obtained, and this nonlinear region should be attained at lower wavelength, and at lower concentrations for long fibers having a high aspect ratio. We further predict that the relative absorptionA(λ1)/A(λ2) where λ1 < λ2, should decrease with fiber dimension.The ATR signal at 303 cm−1, corresponding to a lattice vibration, varies linearly with fiber concentration up to 100 μg/cm2, whereas the intensity of this band relative to the OH stretching band at 3690 cm−1is a monotonic function, representing the fiber morphology. Dust levels and fiber morphology established from the IR-ATR spectroscopy are consistent with measurements by light and electron microscopy.

ISSN:0008-4042    

DOI:10.1139/v84-076

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The crystal structures of twoendo-endo-dienes, 5,6,7,8,9,9-hexachloro-1,4,4a,5,8,8a-hexahydro-endo-endo-1,4-ethano (and propano)-5,8-dimethanonaphthalene,1band1chave been determined. These, together with the methano-homolog1a(of known structure), are shown to exhibit decreasing across-space double-bond/double-bond repulsion which correlates with the observed decrease in the ease of cyclization in solution.

ISSN:0008-4042    

DOI:10.1139/v84-077

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Phase diagrams and thermodynamic properties of five additive molten salt ternary systems and nine reciprocal molten salt ternary systems containing the ions Li+, Na+,, OH−are calculated from the thermodynamic properties of their binary subsystems which were obtained previously by a critical assessment of the thermodynamic data and the phase diagrams in these binary systems. Thermodynamic properties of ternary liquid phases are estimated from the binary properties by means of the Conformal Ionic Solution Theory. The ternary phase diagrams are then calculated from these thermodynamic properties by means of computer programs designed for the purpose. It is found that a ternary phase diagram can generally be calculated in this way with a maximum error about twice that of the maximum error in the binary phase diagrams upon which the calculations are based. If, in addition, some reliable ternary phase diagram measurements are available, these can be used to obtain small ternary correction terms. In this way, ternary phase diagram measurements can be smoothed and the isotherms drawn in a thermodynamically correct way. The thermodynamic approach permits experimental data to be critically assessed in the light of thermodynamic principles and accepted solution models. A critical assessment of error limits on all the calculated ternary diagrams is made, and suggestions as to which composition regions merit further experimental study are given.

ISSN:0008-4042    

DOI:10.1139/v84-078

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Metallo tetraphenylporphyrins form 1:1 molecular complexes with 4,6-dinitrobenzofuroxan. The molecular association is described in terms of π–π interaction with porphyrins functioning as donors. The association constants and thermodynamic parameters have been evaluated using optical absorption and1H nmr spectral methods. Based on the binding constants, the donor ability of various metalloporphyrins can be arranged in the following order: Pd(II) > Co(II) > Cu(II) > Ni(II) ~ VO(IV) ~ 2H > Zn(II). Electron paramagnetic resonance studies of the complexes reveal that the π-complexation results in changes in the electronic structure of the central metal ions which are reflected in the changes in the M–N σ bonding. The dipolar contribution to the acceptor proton chemical shifts in the CoTPP complex has been partitioned from ring current contributions using the shifts observed in the ZnTPP complex. The shifts, along with the line broadening ratios observed for the CoTPP complex, are used to arrive at the possible solution structures of the complexes.

ISSN:0008-4042    

DOI:10.1139/v84-079

出版商:NRC Research Press    

年代:1984

数据来源: NRC