摘要:

A kinetic electron spin resonance study of the self-reaction of SF5and a spectroscopic and kinetic e.s.r. study of the reaction of SF5with 1,1-di-t-butylethylene are reported. This radical undergoes self-reaction by a second-order process and the rate constants are given by the Arrhenius equation log 2k1(M−1s−1) = (10.3 ± 0.5) − (1.7 ± 0.5)/θ where θ = 2.303RT kcal mol−1. It adds to 1,1-di-t-butylethylene to give (t-Bu)2CCH2SF5which decomposes by a first-order process with rate constants that obey the expression logk2(s−1) = (13 ± 0.4) − (10 ± 0.2)/θ. Both these rate constants are pertinent to kinetic studies of the photoinduced addition of SF5C1 to olefins.

ISSN:0008-4042    

DOI:10.1139/v75-332

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The rate constants and equilibrium constant for the proton transfer reactionhave been measured at 296 ± 2 K using the flowing afterglow technique:kforward = (2.9 ± 0.6) × 10−9 cm3molecule−1s−1,kreverse = (1.8 ± 0.4) × 10−10 cm3molecule1 s−1, andK = 16 ± 2. The measured value ofKcorresponds to a standard free energy change, ΔG296°, of −1.6 ± 0.1 kcal mol−1which provides values for the standard enthalpy change, ΔH298°= −1.0 ± 0.2 kcal mol−1, the bond dissociation energy, D00(H—CN) = 124 ± 2 kcal mol−1, and the proton affinity, p.a.(CN−) = 350 ± 1 kcal mol−1.

ISSN:0008-4042    

DOI:10.1139/v75-333

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The molecular and crystal structure ofcis-dichlorobis (dimethylsulfoxide) platinum(II),cis-[PtCl2(DMSO)2], has been studied by X-ray diffraction. The compound belongs to the mono-clinicP21/cspace group and the cell parameters are:a = 8.653,b = 13.580,c = 10.914 Å, β = 123.43°, andZ = 4. The refinement of the positional and anisotropic thermal parameters, carried out by full matrix least-squares calculations, converged toR = 0.029 andRw = 0.027.The coordination around the platinum atom is planar. As expected, the DMSO molecules are bonded to the platinum atom through sulfur. The bond distances found are: Pt—Cl = 2.306, 2.312 Å; Pt—S = 2.244, 2.229 Å; S—O = 1.469, 1.454 Å, and S—C = 1.77 to 1.79 Å. The crystal consists of layers of molecules parallel to theacplane.

ISSN:0008-4042    

DOI:10.1139/v75-334

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The kinetics of interaction of hematoporphyrin IX with Cu(II) has been studied in an acetic acid – water solvent (50%–50% v/v). The reaction is of first order with respect to the porphyrin whereas the order with respect to copper(II) perchlorate is smaller than one. This is explained by taking into account the interaction between Cu2+and acetic acid. The reactive species are Cu2+, CuOAc+, and free porphyrin. The mechanism of the reaction is compared to those proposed for similar systems.

ISSN:0008-4042    

DOI:10.1139/v75-335

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

This paper reports the i.r. and u.v. spectra of severalN-p-tolylsulfonylsulfilimines and several newN-p-ethylbenzenesulfonylsulfilimines have been examined.

ISSN:0008-4042    

DOI:10.1139/v75-336

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

A number of polycyclic aromatic thiones have been prepared from the corresponding ketones. Several of the thiones in which there is a freeperiposition cyclize, on excitation in the π* ← n band, to give thiophene derivatives. The structures of these were proven by application of physical methods and by desulfurization to the corresponding benzyl derivatives. The formal hydrogen 1,3 migration involved was, in one case, shown to be intermolecular by the incorporation of deuterium, from deuterium oxide, during the irradiation. In the case of the α-naphthyl derivative, the mechanism of the reaction has been investigated and it has been concluded that the n,π* singlet is the responsible entity.

ISSN:0008-4042    

DOI:10.1139/v75-337

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Sonolysis at 450 kHz degrades an aqueous solution of thymine into at least six products of which four, 5-hydroxymethyluracil,cis- andtrans-5,6-dihydroxy-5,6-dihydrothymine, and urea have been identified and a fifth tentatively assigned asN-formyl-N′-pyruvylurea. A mechanism of sonolytic degradation is proposed.

ISSN:0008-4042    

DOI:10.1139/v75-338

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The analysis ofab initiocharge distributions in cyclohexane and selected methylcyclohexanes indicates that no effect other than that described by the relationship δC = −237.1 qC + 242.64 between C-13 chemical shifts and C net charges (as determined for the alkanes) contributes to any significant extent to the shielding of the carbon atoms. This is no longer true for cyclopropane.

ISSN:0008-4042    

DOI:10.1139/v75-339

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

TheI3C chemical shifts and13C–31P spin–spin couplings (where applicable) are reported for pyridoxine, pyridoxamine, pyridoxal, pyridoxamine phosphate, and pyridoxal phosphate. Resonance assignments are made by consideration of substituent chemical shift effects, as tested on an analogous series of pyridine derivatives. Increased shielding of the C4′ and C5′ methylene groups of the vitamin B6compounds and the methyl groups of 3,4-dimethylpyridine relative to the predicted values are attributed to steric compression. In aqueous solution pyridoxal exists as the hemiacetal form, although at high pHit is in rapid equilibrium with a significant amount of the aldehyde form. Pyridoxal phosphate exists as the aldehyde at high pH, as the hydrated aldehyde at low pH, and in a slow equilibrium between detectable amounts of both species at pH4. The13C–31P couplings through two bonds lie in the range 4.5 ± 0.5 Hz found for a variety of other organic phosphates. The couplings through three bonds indicate a preference for atransarrangement of the phosphorus and ring carbon-5.

ISSN:0008-4042    

DOI:10.1139/v75-340

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Octamethylcyclotetraphosphazene is deprotonated by methyllithium to form carbanions, which react with methyl iodide to give ethyl derivatives N4P4Me8−nEtn,the structure of the dihydrochloride of the diethyl derivative, N4P4Me6Et2•2HCl has been determined. Its crystals are monoclinic,a = 9.928(5),b = 15.482(6),c = 6.329(2) Å, β = 103.29(2)°, space groupP21/n. The structure was determined from diffractometer X-ray data and refined by full-matrix least squares methods toR0.079 for 715 observed reflections. The N4P4Me6Et2H22+ion lies on a crystallographic center of symmetry and the eight-membered phosphazene ring has the "chair" conformation. There are two significantly different P—N bond lengths, 1.665(6) and 1.572(7) Å, and two significantly different P—N—P angles, 126.7(6) and 139.8(6)°. The mean P—C bond length is 1.801(7) Å, and the mean N—P—N and C—P—C angles are 112.2(4) and 107.6° respectively. Bond lengths and angles in the phosphazene ring show the characteristic effects of π-electron localization found in other protonated phosphazene derivatives. The two ethyl groups are intran-antipodal positions, corresponding to the least intramolecular electrostatic repulsion in the carbanion.

ISSN:0008-4042    

DOI:10.1139/v75-341

出版商:NRC Research Press    

年代:1975

数据来源: NRC