摘要:

The thermal chemistry of a series of substituted 1-aryl-3-methyl-2-phenyl-1-diazobut-2-enes has been examined. These vinyldiazo compounds react in two parallel pathways: cyclization to a 3-aryl-5,5-dimethyl-4-phenyl-5H-pyrazole or loss of nitrogen and cyclization to a 1-aryl-2-phenyl-3,3-dimethylcyclopropene presumably by a vinylmethylene intermediate. The kinetics of these processes reveal quite different substituent effects. The relation of these results to the stability of the vinylmethylene produced and to the singlet photochemistry of cyclopropene derivatives is discussed.

ISSN:0008-4042    

DOI:10.1139/v79-229

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The complexation of nickel(II) with triethylenetetramine andD-penicillamine has been examined in 0.15 MNaCl solution at 25 °C by a combined potentiometric–spectroscopic approach. Trien (A) forms the following complexes with Ni(II): MA, MA2, MH2A2, M2A3, M2HA3, and M2H2A3with overall log stability constants: 14.34, 20.64, 37.28, 40.05, 49.20, and 55.02, respectively. Their concentrations as a function of pH are presented and their likely structures discussed. In contrast,D-penicillamine forms the species MA and MA2only. The latter species, which is the only species from pH 5.8 to 10.0, is shown to be square-planar via coordination of the N, S atoms of the ligand molecules. The overall log stability constants of MA and MA2are 11.22 and 22.71, respectively. The significance of these results in relation to the effectiveness of these ligands in preventing nickel toxicity in rats is discussed.

ISSN:0008-4042    

DOI:10.1139/v79-230

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

A simple method of estimating the fraction of dative structure in molecular complexes using Hammett ρ values is given. A physical interpretation of the parametermin the equation,hν = mID + n, relating the charge-transfer energy,hν, of a molecular complex and the ionization potential,ID, of the donor is given.

ISSN:0008-4042    

DOI:10.1139/v79-231

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Long-range spin–spin coupling constants between sulfhydryl protons and ring protons in some halothiophenol derivatives in CCl4solutions are reported. In contrast to the corresponding phenol derivatives, substantial amounts of out-of-plane conformers are present at 305 K for all but 2,6-dichlorothiophenol. Thecisandtransconformers differ by only about 0.2 kcal/mol in free energy for 2,4-dibromothiophenol and 2,4-dichlorothiophenol, in good agreement with a recent analysis of the dipole moment observed for the latter compound. The barrier to internal rotation of the sulfhydryl group is considerably smaller than for a hydroxyl group and rough estimates are given for the barrier in a few compounds. For example, the barrier in 2,3,5,6-tetrafluorothiophenol is lower than in 2,6-dichlorothiophenol. STO-3G MO calculations overestimate the internal barrier to rotation of the sulfhydryl group, but yield charge densities for this group which indicate that a major cause of the relative weakness of its intramolecular hydrogen bonds resides in its lack of polarity.

ISSN:0008-4042    

DOI:10.1139/v79-232

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

This paper reports13C chemical shifts for 20 methylgermanium compounds. These shifts are correlated against (i) the electronegativity of halogen in the Me3GeX compounds, (ii) the calculated charge on the carbon atom, (iii) the1H shifts of the methyl protons, and (iv) the13C shifts for the analogous carbon, silicon, and tin compounds.

ISSN:0008-4042    

DOI:10.1139/v79-233

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The anions from β-keto esters or β-diketones were reacted with diethyl phosphorochloridate to yield the corresponding enol phosphates. These enol phosphates were coupled with dialkylcuprates to produce the β-substituted α,β-unsaturated esters or ketones in good yield. Starting from acyclic β-keto esters this sequence was used to stereoselectively generate tri- and tetrasubstituted olefins.

ISSN:0008-4042    

DOI:10.1139/v79-234

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Protonated 4,4-dimethylcyclohex-2-enone,1H, has been shown to isomerize on irradiation in FSO3H at −85 °C to give protonated 6,6-dimethylbicyclo[3.1.0]hexan-2-one,5H, and protonated 3-isopropylcyclopent-2-enone,4H. The protonated bicyclic ketone5Hwas found to be both thermally and photochemically labile, in both instances rearranging to4H. The first order rate constant for the thermal isomerization of5Hto4Hat −60 °C was 1.73 × 10−4 s−1. As5Hwas shown to be photolabile in the presence of1H, it was not possible to establish whether4Hwas a primary photoproduct of1H. No photoisomerizations of protonated cyclohex-2-enone and protonated 4-methylcyclohex-2-enone could be detected. The photoisomerization of protonated Δ1,9-10-methyl-2-octalone has been re-examined at low temperature in an attempt to detect tricyclic products.

ISSN:0008-4042    

DOI:10.1139/v79-235

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Paramono- or disubstituted chiral benzhydrols have been studied by nmr in the presence of Eu(dcm)3. The influence of association constants and structural parameters has been assessed separately. The observed nonequivalence cannot be related to a difference between the association constants but is primarily due to a difference between the geometries of the lanthanide–substrate complexes, correlated with the electronic nature of the substituents. A rule for the determination of the absolute configuration of such compounds has been established.

ISSN:0008-4042    

DOI:10.1139/v79-236

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Phacidin, an antifungal antibiotic, isolated from the canker fungusPotebniamycesbalsamicolaSmerlis var.boyceiFunk is shown to be 2-methoxy-6-nonanoyl-4H-pyran-4-one-3-carboxaldehyde. Carbon-13 nmr spectra of phacidin and several related γ-pyrones are discussed.

ISSN:0008-4042    

DOI:10.1139/v79-237

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The tropane-3-spiro-5′-hydantoin (α isomer) obtained from tropinone by the Bucherer–Bergs reaction has been shown by13C nmr and X-ray diffraction studies to have the 4′-carbonyl group in the equatorial position; the β isomer, obtained via the Strecker reaction, has this group axial. The results of these two reactions oncis-bicyclo[3.3.0]octan-3-one and oncis-3,4-dimethylcyclopentanone show, on the basis of the1H nmr,13C nmr, and X-ray diffraction studies of the products, a stereochemical course related to the preferred conformation of the cyclopentane rings.

ISSN:0008-4042    

DOI:10.1139/v79-238

出版商:NRC Research Press    

年代:1979

数据来源: NRC