摘要:

The photochemical insertion reaction of SnCl2into the metal–metal bond of [P(n-C4H9)3Co(CO)3]2has been studied in THF at 23.0 °C at the irradiating wavelengths 365 nm, 436 nm, and 546 nm. At 365 nm, the quantum yield for the reaction increases with increasing concentration of SnCl2and approaches a limiting value of 1.0. At 436 nm, however, the quantum yield increases above 1.0 and at 546 nm, quantum yields as high as 6 were measured. The uv–visible absorption spectrum of [P(n-C4H9)3Co(CO)3]2shows an intense band at 372 nm and a broad shoulder at about 440 nm. A simple mechanism is proposed to operate on irradiation at 365 nm due to absorption by the intense band, but a more complicated chain mechanism is suggested to operate at 546 nm as a result of absorption by the lower energy shoulder band. It appears that both mechanisms operate on irradiation at 436 nm due to the overlap of the two absorption bands at this wavelength.

ISSN:0008-4042    

DOI:10.1139/v77-312

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The electron paramagnetic resonance (epr) spectra of the diarylmethylenes: diphenylmethylene,p-cyanodiphenylmethylene,p-methoxydiphenylmethylene,p,p′-dimethoxydiphenylmethylene,p,p′-dicyanodiphenylmethylene,p-cyano-p′-methoxydiphenylmethylene, have been studied. The zero-field splitting parameters have been determined. The signal intensity as a function of temperature (ca. 4–20 K) indicates these methylenes are ground state triplet species.

ISSN:0008-4042    

DOI:10.1139/v77-313

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Two postulates simplify the evaluation and algebraic complexity of the expression for the anharmonic correction to the ground rotational–vibrational energy of a polyatomic molecule. The two postulates are: (1) anharmonicity of vibration is associated with bond stretching coordinates only; all other internal coordinates can be represented by harmonic potentials; (2) bonds vibrate according to a Morse potential. The result is the replacement of tedious computer calculations by a 'back of an envelope' type of computation. Relationships between anharmonic corrections to the ground state vibrational energies of isotopically different molecules are derived. Good agreement with exact results is obtained. Quantitative and qualitative applications are given.

ISSN:0008-4042    

DOI:10.1139/v77-314

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The interpretation of the temperature dependent nmr spectra of the three thiobenzmorpholides1–3in terms of torsional libration proposed in the title article is criticized. Pure samples ofcis-1andtrans-1have been prepared and studied by dynamic1H and13C nmr. A new interpretation is presented which involves the freezing of the passage over the steric barrier with a planar Ph—C(S)N transition state.

ISSN:0008-4042    

DOI:10.1139/v77-315

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The infrared absorption spectra in different physical states (liquid, solution, vapor) and the Raman spectra in the liquid or solid state of di- and trisubstituted isothiazole derivatives have been analyzed. For some compounds a study of the normal vibrations has also been done. An assignment of the fundamental modes of vibration of these molecules is given and discussed.

ISSN:0008-4042    

DOI:10.1139/v77-316

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The acetolysis in the presence of AgOAc of tri-p-tolylvinyl-2-13Cbromide (3-Br-2-13C) gave about 14% scrambling of the label from C-2 to C-1 due to degenerate 1,2-tolyl shifts. This value is compared with the 7 and 20% scramblings previously observed for similar reactions with triphenylvinyl-2-13Cand trianisylvinyl-2-13Cbromides, and their mechanistic implications are discussed. The trifluoroacetolysis of3-Br-2-13Cin the presence of CF3COOAg or CF3COONa resulted in about 47% scrambling. In the absence of any added salt, the scrambling was found to increase with reaction time and in addition, solvent isotope effects of 1.6 and 2.6, respectively, were observed forat 100 °C with or without added CF3COONa. The role of electrophilic addition–elimination and the processes leading to the isotopic scrambling in the reaction with CF3COOH, with or without added salt, are discussed.

ISSN:0008-4042    

DOI:10.1139/v77-317

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Mercaptide anions react with chlorinated sulfones in two modes,i.e. nucleophilic attack on carbon with chlorine as the leaving group and/or nucleophilic attack on chlorine with concomitant carbanion formation. Mercaptide anion pKb, degree of chlorination of the sulfone substrate, and substituent effects are qualitatively assessed in terms of the propensity for nucleophilic attack at carbon or chlorine.

ISSN:0008-4042    

DOI:10.1139/v77-318

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

1-Haloalkanesulfinic acids react with water,p-toluidine, or an enamine in the presence of added base to give products expected from an intermediate sulfene. It is concluded that sulfenes are formed, and hence may be presumed to react, via the 'abnormal route',i.e., loss of a nucleophile from thecarbon(rather than the sulfur) of the incipient sulfene, or, for the reverse process, addition of a nucleophile to thecarbon(rather than the sulfur) of the sulfene. Since addition at the sulfur is well precedented, these conclusions indicate that sulfene is an 'ambifunctional' electrophile of a previously unknown kind. The mechanism of the sulfene formation is discussed in the light of deuterium labelling and kinetic experiments.

ISSN:0008-4042    

DOI:10.1139/v77-319

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The protonation of eleven thioamides, five thioureas, and four thionbenzoates in aqueous sulfuric acid has been found to follow theHTacidity function with acceptable accuracy. Protonation constants pKTH+obtained by use ofHTagreed fairly well with pKTH+values obtained by the Bunnett–Olsen method, but less well with those obtained by the Marziano–Cimino–Passerini procedure. Linear free-energy relationships of pKTH+values are discussed.

ISSN:0008-4042    

DOI:10.1139/v77-320

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Studies on the biodegradation of (+ )-usnic acid (1) by aPseudomonasspecies have revealed a novel aromatic deacylation process. The isolated metabolite, (+)-6-desacetylusnic acid (2) is crystalline and its structure is established by means of spectroscopic and chemical methods. The synthesis of2from usnic acid (1) is also reported and provides conclusive evidence for the structure of this metabolite.

ISSN:0008-4042    

DOI:10.1139/v77-321

出版商:NRC Research Press    

年代:1977

数据来源: NRC