摘要:

The equilibrium constant in dioxane between azido and tétrazole isomers has been obtained for five heterocyclic azides (2-azido thiazoles, benzothiazole, benzoxazole, and 3-azido isoxazole) by proton nmr and dipole moment- studies. The last method involves a comparison between experimental and calculated (INDO, CNDO/2, CNDO/S) dipole moments. The CNDO/S method gives the best equilibrium constants and entropy factor (ΔS ∼ 50 J K−1 mol−1). A value of 114° for the C—N—N angle is found to account satisfactorily for certain properties (energy, dipole moment, photoelectron spectra) of aromatic azides. The heterocyclic azidoimines prefer theZconformation.

ISSN:0008-4042    

DOI:10.1139/v77-244

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Infrared spectra of polycrystalline K2HgCl4.H2O at different degrees of deuteration were recorded, in the 4000–250 cm−1region, at temperatures between liquid-nitrogen and 130 °C. The spectra confirm the existence of a single type of water molecule, engaged in two equivalent hydrogen bonds. The value of 2548 cm−1for the isolated O—D stretching frequency leads to an estimate of 3.25(3) Å for the O … Cl hydrogen-bond distance, in excellent agreement with the results of X-ray and neutron diffraction. Dynamic coupling is appreciable for stretch, bend, and librational fundamentals but is weaker than in CuCl2.2H2O or K2CuCl4.2H2O, in which the water molecules in the crystal are more tightly bonded.A number of corrected values are reported of isolated O—D stretching frequencies in hydrates studied previously.

ISSN:0008-4042    

DOI:10.1139/v77-245

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

We review the formulation and solutions of a number of extremal problems associated with points and unit charges on the surface of a sphere in E3. For one of these problems, namelywheredpqis the Euclidean distance between pointsPandQandmis the number of points, we discuss the results form ≤ 16 and 1 ≤ n ≤ ∞. For the casesm = 5, 11, 13–16 we find hitherto undiscovered solutions. Our solutions form = 5 and 11 correct earlier results in the literature. We also sharpen the existing literature results form = 7 and 10.

ISSN:0008-4042    

DOI:10.1139/v77-246

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Aqueous H3NTA, H2MIDA, H2IDA, and their anions decompose under hydrothermal conditions (400–580 K) according to first order kinetics by successive decarboxylations, oxidation by O2being unimportant except at the highest temperatures. In the presence of added H+, the species H4NTA+and, to a lesser extent, H3MIDA+(but not H3IDA+), provide significant decomposition pathways through elimination of a —CH2COO— group (deacetylation). For HnNTA(3−n)−, first order rate coefficientsknfor decomposition arek0 = 4.5 × 10−7,k1 ∼ 1 × 10−6,k2 ∼ 7 × 10−5,k3 = 2.1 × 10−4, andk4 = 1.0 × 10−2 s1, at 503 K and ionic strength 2.0 m, the spread in rates being due to differences in ΔS*rather than ΔH*. H2MIDA and H2IDA are comparable in reactivity to H3NTA, while their anions are much less reactive than the NTA species of the same charge. The good thermal stability of aqueous NTA commends it as a reagent for boiler servicing and for decontamination of water-cooled nuclear reactors. A potentiometric method for the estimation of mono-, di-, and tribasic aminoacids in aqueous mixtures of these is described.

ISSN:0008-4042    

DOI:10.1139/v77-247

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The kinetics and mechanism of decomposition of NTA complexes of FeIII, FeII, CoII, NiII, and CuIIunder hydrothermal conditions (425–573 K) have been examined. The relative rates at 573 K are CoIINTA−< NTA3−< NiIINTA−< FeIIINTA0< H3NTA0< CuIINTA−< H4NTA+. Aqueous CoIINTA−and FeIINTA−, like NTA3−, decomposed at 573 K by decarboxylation, precipitating Co(OH)2and Fe3O4respectively; NiIINTA−precipitated Ni(OH)2initially but subsequently Ni metal. At 530 K, FeIIINTA0solutions precipitated FeII3(NTA)2•H2O, but at higher temperatures Fe3O4formed, the NTA ligand being reduced to HCHO and iminodiacetate (IDA) rather than decarboxylated. Similarly, CuIINTA−gave IDA and HCHO at temperatures as low as 425 K, forming first CuI(which precipitated as CuCl in the presence of Cl−) and then metallic Cu. The applicability of NTA to corrosion control in boilers and to60Co removal from water-cooled nuclear reactors is briefly considered. The half-life of FeIIINTA in the hydrosphere is estimated at 80 years (cf. 8 × 106years for free NTA), in the absence of photolysis or biodégradation.

ISSN:0008-4042    

DOI:10.1139/v77-248

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The infrared spectra between 330 and 15 cm−1of the structure I clathrate hydrates of ethylene oxide, cyclopropane, and trimethylene oxide, at 4.3 K are presented. The spectra have an unusually high signal-to-noise ratio made possible by a Michelson interferometer and a silicon bolometer detector which operates at 1.2 K. Rotational vibrations of the guest molecules were observed at 65.0 and 35.6 cm−1for ethylene oxide and at 69 and 50 cm−1for trimethylene oxide. Inter-guest coupling of rotational vibrations is small and the two frequencies are assigned to vibrations about different inertial axes. The resulting force constants are 487 and 264 ferg rad−2for ethylene oxide and 1190 and 1130 ferg rad−2for trimethylene oxide and are discussed in relation to the barriers to reorientation of the guest molecule. The bands due to these vibrations are fairly sharp at 4.3 K, but are broad and poorly defined at 100 K. The guest and water vibrations interact predominantly through their transition dipoles, although the main contribution to the force constants of the rotational vibrations is from steric forces. The absorption by the water vibrations above 100 cm−1is very similar for ethylene oxide and cyclopropane hydrates but significantly different for trimethylene oxide hydrate. Strong objections exist to the obvious interpretations of this difference which remains unexplained.

ISSN:0008-4042    

DOI:10.1139/v77-249

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Conversion of the alcohol4into the mesylate5and reduction of the latter with LiAlH4under mild conditions afforded ishwarane1in 65% yield, thereby providing a further demonstration of the synthetic utility of such reductive, homoallylic cyclizations and a substantially improved synthesis of ishwarane.

ISSN:0008-4042    

DOI:10.1139/v77-250

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Reaction of alkyl (aryl) sulfonyl chlorides and sulfonic acid anhydrides with pyridine in the presence of sodium borohydride affordN-sulfonyl-1,4-dihydropyridines (1) andN-sulfonyl-1,2-dihydropyridines (2). The ratio of products (1:2) was dependent upon solvent and temperature. Reaction of2dwith 4-phenyl-1,2,4-triazoline-3,5-dione (4) afforded theendo-adduct5.

ISSN:0008-4042    

DOI:10.1139/v77-251

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The formation of a visible oxide film on polycrystalline Pt foil and wire is reported, and positively identified. The conditions for growth and dissociation of the oxide are outlined, and the energy of decomposition is estimated.

ISSN:0008-4042    

DOI:10.1139/v77-252

出版商:NRC Research Press    

年代:1977

数据来源: NRC