摘要:

The reactions oftrans-[PtH(PEt3)2(acetone)]+andtrans-[PtH(PEt3)2(CO)]+with a variety of acetylenes are described. The geometries of the products with respect to the platinum centre and to the stereochemistry of the alkenyl group have been determined on the basis of their1H nmr parameters. For reactions with the cation containing acetone, and particularly from a variable temperature1H nmr study of its reaction with 2-butyne in the presence of water, the insertion pathway is shown to be entirely analogous to that for olefin insertion, involving an initial displacement of thetransligand by acetylene, isomerization to acis-like intermediate, migratory insertion rearrangement, and re-combination with an appropriate ligand to give eithercisortransplatinum products. The insertion pathway with the carbonyl cation is dependent on the nature of the acetylene; for non-activated or weakly activated acetylenes insertion occurs via five-coordinate intermediates, but with strongly activated acetylenes, the same mechanism as with the acetone cation appears to occur, involving reversible loss of carbon monoxide.

ISSN:0008-4042    

DOI:10.1139/v77-031

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The reactions of platinum(II) hydrides,trans-PtHXL2, where X = NO3, Cl or CH3OH, and L = PEt3or tricyclohexylphosphine, with disubstituted acetylenes, R1C≡CR2have been examined under a variety of conditions. From spectroscopic parameters, the gross geometry at platinum as well as the geometry of the resulting alkenyl groups in the products have been determined. The observation that all alkenyl groups have acisgeometry is consistent with a migratory insertion step involving a four-centred transition state, in which the disposition of the acetylene relative to the Pt—H bond appears to be dependent on the Pt—H bond polarity. Evidence is presented to demonstrate that this polarity depends on several factors including solvent, and ligands on Pt(II). For L = tricyclohexylphosphine, the occurrence of a side reaction which competes with insertion and which leads to a Pt(0) acetylene complex is also demonstrated, and other interesting reactions are described.

ISSN:0008-4042    

DOI:10.1139/v77-032

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The silver–pyrazole metal-complex electrode was investigated and used to determine free concentrations of pyrazole in the presence of Cd2+, Zn2+, Ni2+, or Co2+ion, under different pyrazole/divalent metal concentration ratios. The stability constants of the complexes formed between these ions and pyrazole were calculated.

ISSN:0008-4042    

DOI:10.1139/v77-033

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Ozone yields have been measured from the Febetron irradiation of mixtures containing 1–50 mol% oxygen and each of the five rare gases. The maximum values ofG(O3) calculated using the energy absorbed only in the rare gas are obtained with the addition of less than 10% oxygen and are for: He, 16; Ne, 14; Ar, 11; Kr, 10; Xe, 12; each with an uncertainty of less than ±10%. On the addition of 0.2 mol% SF6these yields are reduced to 6,5,1,2, and 2.5 respectively.These values are compared with those derived from ion and excited state yields and the contributions of subexcitation electrons.

ISSN:0008-4042    

DOI:10.1139/v77-034

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Pleiadiene,27, can be efficiently prepared in 45% yield by copper catalyzed intramolecular coupling of the bis-Grignard reagent of 1,8-trans-(β-bromovinyl)naphthalene,5. Also obtained in 6% yield is the unsaturated 14-membered ring compound28. Whereas the bis(β-bromovinyl) compound5is readily available from 1,8-divinylnaphthalene, α-bromovinyl compounds are obtained from divinylbenzenes. On coupling the Grignard reagent from 1,4-bis(β-bromovinyl)-benzene, only linear dimeric products were obtained.

ISSN:0008-4042    

DOI:10.1139/v77-035

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

13C spin–lattice relaxation studies on lecithin bilayers indicate a marked destabilization of the bilayer structure by incorporated vitamin E (d,l-α-tocopherol) and phytanic acid, phytanic acid causing the greatest perturbation.Kinetic analysis of paramagnetic praseodymium infusion into the lecithin vesicles containing various phytyl compounds has been performed using31P nmr. Relative rates of Pr3+leakage through the mixed lecithin – phytyl compound bilayer compared with pure lecithin (relative rate = 1.00) were: phytol = 7.8, vitamin E = 47.7, and phytanic acid = 2897.

ISSN:0008-4042    

DOI:10.1139/v77-036

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The OH and NCH2proton signals of 1-(2′-hydroxythiobenzoyl)-2-methylpiperidine (2) are resolved into separate peaks assigned to four conformers (EA, EB, ZA, andZB) in 220 MHz nmr spectra at −50 °C. All have a strong intramolecularhydrogen bond. TheZBandEBconformers have the lowest and highest ground state energies, respectively. Exchanges betweenAandBconformers have a higher energy barrier than exchanges betweenZandEisomers, but by +40 °C all four conformers interchange rapidly. The nature of all possible interchange processes is considered and a potential energy surface with respect to rotation about the Ph—C(S) and C—N bonds is presented. For the 4-methyl analogue of2low temperature nmr spectra exhibit two sharp OH signals arising fromAandBconformers. For 2,6-di-methyl-4-(2′-hydroxythiobenzoyl)morpholine theA/BOH doublet of thecisdimethyl isomer can be distinguished from that of thetransisomer. Thus it is demonstrated that the intra-molecularly hydrogen bonded OH proton is a good spectroscopic conformational probe. Nuclear magnetic resonance, ir, and uv data all indicate that in the 2,6-dimethylpiperidine analogue of2the CNC and Ph—C(S)N planes are perpendicular due to steric interference. Coplanarity of the phenyl ring with the thioamide group is attributed to a very strong intramolecularhydrogen bond, in equilibrium with a proton transferredform in solution. This structure resembles the transition state for rotation in the most readily achieved exchange between conformers of2.

ISSN:0008-4042    

DOI:10.1139/v77-037

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The reaction of thiophosgene with α-diazocarbonyl compounds produced mixtures of 1,2,3-and 1,3,4-thiadiazoles, in which the latter predominated, irrespective of whether the bis(α-diazoacyl)mercury derivatives or the free diazo compounds were used. In contrast, ethyl chlorodithioformate gave exclusively 1,3,4-thiadiazoles with α-diazocarbonyl compounds in the presence of triethylamine and only 1,2,3-thiadiazoles when the bis(α-diazoacyl)mercury derivatives were used.

ISSN:0008-4042    

DOI:10.1139/v77-038

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

A general route to 3-substituted cyclohepta-1,4-dienes is described in this paper. 7-Substituted cycloheptatrienes were used as starting materials and these were reacted with 4-phenyl-1,2,4-triazoline-3,5-dione to give 4 + 2 cycloaddition products of the norcaradiene form of the cycloheptatrienes. Catalytic reduction of these adducts gave 9-substituted 4-phenyl-2,4,6-triazatetracyclo[5.3.2.02,6.08,10]dodeca-3,5-diones in good yield. Basic hydrolysis of the hetero-cyclic ring of these products followed by Cu2+oxidation of the resulting hydrazo compounds gave the copper complexes of substituted 6,7-diazatricyclo[3.2.2.02,4]non-6-enes. The azo compounds, formed on decomplexation of the copper complexes, readily lost nitrogen to give 3-substituted cyclohepta-l,4-dienes. Care had to be taken during these last steps as the cyclo-heptadienes with carboxylate substituents very readily isomerized to the conjugated isomers. The pmr spectra of the cyclohepta-l,4-dienes and related cycloheptatrienes are compared and discussed in terms of the presence of an induced diamagnetic ring current in the latter systems.

ISSN:0008-4042    

DOI:10.1139/v77-039

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The diamagnetic susceptibilities of several 7-substituted cycloheptatrienes have been measured and used in conjunction with estimated values of their susceptibilities (Haberditzl increment system) to obtain the susceptibility exaltations of these compounds. These exaltations were found to be very large and to vary as a function of the size of the C7substituent. There was no apparent correlation of the exaltation of a compound with the electronic properties of its substituent. The effect of a substituent on the susceptibility exaltation is interpreted in terms of conformational changes in the seven-membered ring. The magnitude of the susceptibility exaltations of these cycloheptatrienes, for example 7-tert-butylcycloheptatriene (Λ = 14.8), in comparison to that of benzene (Λ = 13.7) would suggest that the presence of an induced diamagnetic ring current is not a good criterion of its aromaticity.

ISSN:0008-4042    

DOI:10.1139/v77-040

出版商:NRC Research Press    

年代:1977

数据来源: NRC