摘要:

The gas phase ion–molecule reactions and proton affinity of borazine have been investigated by both theoreticalab initioand ion cyclotron resonance techniques. The experimental proton affinity has been determined from competitive proton transfer equilibria with standard reference bases and found to be 196.4 ± 0.2 kcal/mol. Ion–molecule reaction schemes for reaction of borazine molecular ions have been proposed.Ab initiocalculations find the proton affinity of borazine to be 203.4 kcal/mol and the most energetically favorable structure of the borazinium ion is one in which very little structural change occurs relative to neutral borazine with the exception of the geometry about the protonated nitrogen atom. Charge distributions and bond lengths are used to explain bonding changes upon protonation.

ISSN:0008-4042    

DOI:10.1139/v79-280

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Evidence is presented for the composite nature of the solvated (or trapped) electron absorption band in LiCl aqueous glass at 77 K. It is shown that the overall visible absorption spectrum can be deconvoluted into a homogeneously-bleachable 'green' band and a heterogeneously-bleachable 'red' band, whose relative magnitude and absorption band-maxima change with the concentration of electrolyte. From the combined results of time-resolved and steady-state photobleaching experiments, it is concluded that at least two unstable bands are formed during photobleaching (with smaller lifetimes for the band lying further towards the infrared) which then reconverted into the 'green' band with over 40% efficiency.

ISSN:0008-4042    

DOI:10.1139/v79-281

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The chromium(II) reduction of the complexes en2Co(3-acetyl-ptdn)2+(1) and en2Co(2-acetyl-btdn)2+(2) has been studied. Both complexes obey the rate lawAt 25 °C,I = 1.0 M(LiClO4),k = (4.5 ± 0.2) × 10−4 M−1s−1, ΔH≠ = 13.0 ± 0.7 kcal mol−1, ΔS≠ = −30 ± 2 eu for complex1andk = (5.6 ± 0.4) × 10−3 M−1s−1, ΔH≠ = 11 ± 1 kcal mol−1, ΔS≠ = −30 ± 4 eu for complex2. Product studies indicate attack at the uncoordinated acetyl functions in both complexes. The results are compared to those obtained for reduction of en2Co(3-formyl-ptdn)2+and en2Co(ptdn)2+by chromium(II).

ISSN:0008-4042    

DOI:10.1139/v79-282

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Total Coulomb interactions between non-bonded atoms behave in general in a 'quasi-additive' fashion, not only in simple linear and branched paraffins, but also in polycyclic hydrocarbons constructed from chair and boat cyclohexane rings. Because of their relative insensitivity to structural features, they cannot be regarded as being the leading terms in the explanation of energetic effects related to structural changes. The prime factors governing molecular stabilities, as well as the explanation of the structural effects which are at their origin, are found in the behavior of the charge dependent energy contributions associated with bonded atoms, i.e., in the chemical bonds themselves.

ISSN:0008-4042    

DOI:10.1139/v79-283

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Normal coordinate calculations have been carried out for the N(SiH3)3molecule. A model withC3hsymmetry was used, which is based on a planar NSi3skeleton. The presence of complex numbers for the characters of degenerate irreducible representations of the point groupC3hleads to an unusual problem when factoring the G and F matrices. A set of real degenerate symmetry coordinates for theE′ andE′′ species can be constructed, but these are not true symmetry coordinates under theC3hpoint group. However, they can be obtained from the genuine (complex) symmetry coordinates by a unitary transformation. For a degenerate species, this procedure leads toaandbblocks of the factored G and F matrices, which contain interaction terms. Consequently both blocks must be taken together when forming the secular equation, and subsequently the calculated frequencies appear as pairs of identical numbers.A valence force field that includes all reasonable interactions has been obtained and used to predict the wavenumbers of the15N andd9isotopic molecules. Details of the normal vibrations in the three molecules have been obtained from potential energy distributions. The results show reasonable agreement with the limited experimental data available for the isotopic molecules.

ISSN:0008-4042    

DOI:10.1139/v79-284

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The reactions of triethylenetetramine with protons and with bivalent Zn, Cd, and Pb have been studied in aqueous solution and in 50% (v/v) aqueous 1,4-dioxane, 25 °C,I = 0.10 MKNO3. logK(potentiometric) and ΔH(calorimetric) data are interpreted in terms of electrostatic effects and solvation effects operative in the two solvents.Protonation constants are higher by 0.2–0.6 log units in aqueous solution. Stepwise enthalpies of protonation −ΔHn(n = 2,3,4) are significantly higher, and the corresponding entropies lower, in aqueous solution. The complexes [ML]2+are of similar stability in the two solvents but −ΔHis ca. 10–20% lower in aqueous dioxane.

ISSN:0008-4042    

DOI:10.1139/v79-285

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Flash photolysis of K−, Rb−, and Cs−in tetrahydrofuran (THF) produces the corresponding ion-pairs (K+, es−), (Rb+, es−), and (Cs+, es−), followed by the regeneration of the parent metal anion, M−. In mixed-metal solutions containing Na and M where M is K, Rb, or Cs, photolysis of Na−also forms the (M+, es−) ion-pair and M−, but with the latter then reforming Na−on an extended time scale. Similar results were obtained in dimethoxyethane (DME) at 213 K, but in this case with the initial formation of a loose ion-pair, (M+, es−)loose.Based on a Gaussian–Lorenztian shape function, the 'best-fit' optical bands for the (M+, es−) and M−species were used to simulate the experimental spectra and deduce the corresponding extinction coefficients in both solvents.The overall mechanism is complex but is in good agreement with previous interpretations deduced by pulse radiolysis.

ISSN:0008-4042    

DOI:10.1139/v79-286

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The electrochemical behavior of the Pb2+/Pb(Hg) system in aqueous and aqueous ethylene glycol solutions is studied in the temperature range of 20.0 to 50.0 °C by means of current reversal chronopotentiometry. It is shown that the reduction of Pb2+ion is reversible and that kinetic or catalytic complications are not present. The value of dE1/2/dTis −0.6 mV/deg in the aqueous solution and −0.5 mV/deg in the solution with 56% (w/w) or higher concentrations of the organic solvent. In the above concentration range of ethylene glycol the activation energies of diffusion and viscosity vary from 4.3 × 103to 7.2 × 103 cal mol−1and from 3.7 × 103to 6.7 × 103 cal mol−1, respectively. For all solutions the solvodynamic mean radius of the diffusing species remains constant within the experimental error, suggesting that the diffusing species is always the hydrated Pb2+ion.

ISSN:0008-4042    

DOI:10.1139/v79-287

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Meso-α,β,γ,δ, tetraphenylporphin derivatives bearing acrylic (cisandtransisomers) and propionic side chains with a terminal imidazole group have been synthesized. Intermediate compounds obtained during their preparation were characterized by visible spectroscopy and nmr. In non-coordinating solvents (benzene or toluene), the iron(III) complexes of these compounds do not show intramolecular coordination of the terminal base on the metal ion. The reduced forms of the compounds have been obtained from ferric forms by heterogeneous reduction with aqueous dithionite and exhibit optical spectra characteristic of five-coordinate ferrous complexes. The nitrogenous bases and carbon monoxide affinities of the latter have been measured and the results indicate that the 'transinfluence' exerted by the terminal imidazole does not depend greatly on the nature and the structure of the covalent side chain. In contrast the stability of the five-coordinate compounds depends on the side chain (transacrylic < propionic <cisacrylic) as suggested by the values reported for the replacement constants of the terminal imidazole by 4-cyanopyridine in unsymmetrical six-coordinate derivatives. The stability of these compounds towards oxidation is also reported.

ISSN:0008-4042    

DOI:10.1139/v79-288

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Low frequency lattice modes ofp-C6H4X2(X = Cl, Br, I),m-C6H4I2, ando-C6H4I2were observed by infrared absorption. Raman scattering spectra were recorded in the case ofm-C6H4I2.When atomic positions were known in the unit cell (p-C6H4X2), the lattice mode frequencies were computed by theGFmatrix method.The agreement between calculated and experimental values is reasonable although we did not consider the multipole–multipole long range interactions.

ISSN:0008-4042    

DOI:10.1139/v79-289

出版商:NRC Research Press    

年代:1979

数据来源: NRC