摘要:

The signs of geminal15N—C—13CH3couplings in configurationally isomeric acetophenone oximes have been determined relative to those of the vicinal15N—C—C—H interactions using an off resonance proton decoupling technique. In theZ-isomer where the nitrogen lone pair iscisto the coupled carbon, the coupling is large and negative, whereas in theE-isomer, the geminal15N—C—13CH3coupling is small and positive in sign.

ISSN:0008-4042    

DOI:10.1139/v77-201

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The electric dipole moments of the bis-1,3-dioxolyl molecule were determined in dilute decahydronaphthalene solution at 25 and 100 °C and in dilute benzene solution at 25 °C. From the temperature dependence of the dipole moment it is concluded that thetransrotamer of the molecule is more stable in both solvents than thegaucherotamer by ∼4.5 kJ mol−1. The conformational behavior of the molecule is discussed in terms of a recently proposed solvation theory.

ISSN:0008-4042    

DOI:10.1139/v77-202

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The resonance Raman spectra of three pharmacologically important sulfonamides, 4-sulfamyl-4′-dimethylaminoazobenzene (1), 4-sulfamyl-4′-hydroxyazobenzene (2), and 4-sulfamyl-4′-aminoazobenzene (3), are compared with those of analogues lacking the sulfonamide group. The —SO2NH2moiety does not directly contribute intense or moderately intense bands to the resonance Raman spectra of1,2, and3. However, —SO2NH2ionization is reflected by frequency changes in a band near 1140 cm−1and intensity changes in the 1420 cm−1region. The normal Raman spectrum of2confirms that the intensity changes reflect —SO2NH2ionization rather than unrelated changes in vibronic coupling. The effect of —OH ionization on the resonance Raman spectrum of2emphasizes that caution must be exercised when relating spectral perturbations to changes in contributions from valence bond type structures. Resonance Raman excitation profiles for the 1138, 1387, and 1416 cm−1bands of2show that these bands gain intensity by coupling with the electronic transitions in the 240 to 450 nm region and that, more than 1000 cm−1to the red of λmax, the wavelength dependence can be closely reproduced by theFBtype terms of Albrecht and Hutley. The excitation profile for each band shows evidence for structure in the 470 nm region, although lack of sufficient excitation wavelengths prevents accurate estimation of the spacing. Under conditions of rigorous resonance the intense Raman lines all occur in the 1400 cm−1region, i.e. they are 'bunched' in the region known to contain the —N=N— stretching vibration.

ISSN:0008-4042    

DOI:10.1139/v77-203

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Crystals of the 3′-Sisomer of the title compound are orthorhombic,a = 23.004(5),b = 11.103(1),c = 7.616(3) Å,Z = 4, space groupP212121. Crystals of the 3′-Risomer are orthorhombic,a = 24.898(1),b = 10.4122(4),c = 7.6467(6) Å,Z = 4, space groupP212121. The structures were solved by direct methods and were refined by full-matrix least squares procedures to finalRvalues of 0.038 for 1466 and 1996 reflections withI ≥ 3σ(I) for the 3′-Sand 3′-Risomers respectively. Both crystal structures consist of discrete molecules linked by systems of intermolecular N—H … O hydrogen bonds and possible weak C—H … O interactions.

ISSN:0008-4042    

DOI:10.1139/v77-204

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

(+)-1-Bromo-2-methylbutane undergoes autoxidation at 1 atm of oxygen and 30 °C to give, after reduction with triphenylphosphine, 1-bromo-2-methyl-2-butanol with a (+) to (−) enantiomer ratio of 1.9 ± 0.2. The optically active 1-bromo-2-methyl-2-butyl radical is, therefore, partially trapped by oxygen at this pressure before it has time to completely racemize. The half-life for racemization of the preferred conformation is approximately 2 × 10−8s−1at 30 °C. At 100 atm of oxygen the yield of (+)-CH3CH2COH(CH3)CH2Br is >90% and the reaction appears to proceed with retention of configuration. A small percentage of (−)-1-bromo-2-methyl-2-butanol is, however, still produced, presumably by inversion of configuration.

ISSN:0008-4042    

DOI:10.1139/v77-205

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The use of high resolution flow nmr has made possible the detection and characterization by nmr of the transient intermediate σ-complex on the actual substitution pathway in the nucleophilic aromatic substitution reaction of 1-ethoxy-2,4-dinitronaphthalene (3) withn-butylamine, and the assignment of its uv-visible spectrum. The intermediate is unambiguously identified as the σ-complex (4) and the reaction is one where the two-step mechanism is clearly applicable.

ISSN:0008-4042    

DOI:10.1139/v77-206

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The interaction between acetylacetone and water in benzene solution has been examined by freezing point depression and nuclear magnetic resonance spectroscopy. The experimental results suggest that a 1:1 associated complex between acetylacetone and water is formed in benzene solution saturated with water, and the association constant is estimated to be 2.4 ± 0.1 (kg solvent/mol). By comparison with the results of methylacetylacetone and dimethylacetylacetone, it is suggested that the enol tautomer of acetylacetone preferentially associates with water.

ISSN:0008-4042    

DOI:10.1139/v77-207

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Reaction of bothperi-dilithionaphthalene andperi-dilithioacenaphthalene with acenaphthenequinone and pyracenequinone yielded the dihydroxy derivatives of acenaphth[1,2-a]-acenaphthylene11a,11b,11cwith no, one, and two ace-bridges respectively. These could be converted either by the Corey thionocarbonate method or with anhydrous liquid hydrogen fluoride to the three alkenes12a,b,cand with Pb(OAc)4to the three diketones13a,b,c. The latter on Wolff–Kishner reduction yielded alkenes12a,band mono ketones15b,c. The uv, ir,1Hmr spectra and electrode reduction potentials for the four series of compounds in which the ace-bridges add increments of strain were examined and possible effects which might be due to strain were noted. Several areas in which theoretical calculations are lacking were noted.

ISSN:0008-4042    

DOI:10.1139/v77-208

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The thermal and photochemical decomposition of formyl azide in the Curtius rearrangement has been studied by means of RHF–LCAO–MO–SCF calculations augmented by CI. The lower electronic states of carbonyl azides, carbonyl nitrenes, isocyanates, cyanates, oxazirenes, nitrile oxides (fulminates), and isofulminates are discussed on the basis of the results for formyl azide and the corresponding isomers of formula CHNO. The discovery of two nearly degenerate states ofA′′ symmetry for formyl azide which may channel decomposition products directly to both isocyanates and carbonyl nitrenes explains some puzzling features of the photolytic Curtius rearrangement. The interconvertibility of the CHNO isomers (and the RCNO isomers) is discussed in terms of the energetics and intended correlations of the accessible electronic states of these species.

ISSN:0008-4042    

DOI:10.1139/v77-209

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The crystal structure of Rb2AgI3, space groupPnma,a = 10.258(2),b = 4.886(4),c = 20.063(10) Å, has been refined. It is isostructural with K2AgI3with chains of corner linked AgI4tetrahedra (Ag—I(bridge) = 2.881 Å, Ag—I(terminal) = 2.834 Å) running alongb. The average bonding distance around the two seven coordinate Rb atoms is 3.722 Å. The polarised Raman spectrum shows the expected 36 modes which are assigned to four different symmetry species. All modes occur with frequencies less than 112 cm−1.

ISSN:0008-4042    

DOI:10.1139/v77-210

出版商:NRC Research Press    

年代:1977

数据来源: NRC