摘要:

X-Ray, continuous-wave and pulsed n.m.r., and dielectric relaxation studies show the hydrate of 1,4-dioxane (D) to be a normal clathrate hydrate of von Stackelberg's structure II with composition D·∼17H2O. The reorientation rate of the relatively large D molecule is slower and the effective activation energy(l.6 kcal/mol) larger than for other guest molecules previously studied in hydrates of the same structure. Weak dielectric absorption associated with reorientation of nondipolar D molecules is attributed mainly to the induction of a total dipole moment of ∼0.2 D in the 28 water molecules of the large structure II cage by two equal and opposed dipoles in the chair form of D.

ISSN:0008-4042    

DOI:10.1139/v75-311

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The kinetics of the palladium(II) acetate catalyzed exchange of vinyl propionate with acetic acid solvent to give vinyl acetate has been studied in the sodium acetate concentration range from 0 to 1 M. The exchange rate first sharply increases as [NaOAc] increases, reaches a maximum at about 0.2 Mand then gradually decreases as the sodium acetate concentration is in-creased to 1.0 M. Using previous results on the equilibrium between palladium(II) acetate and sodium acetate in acetic acid it can be shown that the rate expression for exchange is: rate = (ko + kt[Pd3(OAc)6] + kd[Na2Pd2(OAc)6]) [CH2=CHO2CC2H5] whereko = 2 × 10−4 s−1,kt = 0.045 M−1s−1, andkd = 0.089 M−1s−1. A monomeric palladium(II) species, Na2Pd(OAc)4, formed at high [NaOAc] is unreactive. Since the rate expression does not contain a term in [NaOAc], the sodium acetate serves only to convert one palladium(II) species to another. The lack of a [NaOAc] term in the rate expression for the Na2Pd2(OAc)6catalyzed reaction is believed to result from cancellation of an inhibitory term for π-complex formation by a catalytic term in [NaOAc] in the rate determining conversion of π -complex to σ-complex (acetoxypalladation). Stereochemical studies indicate that acetoxypalladation is nonstereospecific. This result is expected since in the chloride free system acetate is both a ligand and a reactant. Thus it can attack from both inside and outside the coordination sphere of Pd(II).

ISSN:0008-4042    

DOI:10.1139/v75-312

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The reaction of the ditertiary arsines and phosphines fnfars, fnfos, and fnAsP, (L–L), with Fe(CO)5at 150° is a superior route to the complexes (L–L)Fe2(CO)6. Two are reported for the first time (L–L = f6fars, f8fars). The complexes react with monodentate and certain potentially bidentate ligands on u.v. irradiation to afford the monosubstituted derivatives L(L–L)Fe2(CO)5and (L–L)'(L–L)Fe2(CO)5. Spectroscopic studies, in particular magnetically perturbed Mössbauer spectra, indicate that the site of substitution istransto the FeA—FeBbond andcisto the two group V atoms (on FeA). Disubstitution seems to result in further displacement of CO from either FeAor FeB.

ISSN:0008-4042    

DOI:10.1139/v75-313

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

We report data concerning the association of monovalent cations with some polyethyleneglycol ethers that we have prepared.1:1 association constantsKAhave been obtained in methyl alcohol at 25 °C using selective glass electrode potentiometric measurements for Na+and K+and conductimetric measure ments for Cs+and Tl+.The values obtained forKAand for the selectivity ratioKA(K+)/KA(Na+) increase with the number of coordinating sites.Replacement of the two methoxy terminal groups in the chain by primary amide or ester groups reduces the complexing properties of the ligand.The stereochemistry of the coordination is discussed in the case of some biphenylic polyethers.

ISSN:0008-4042    

DOI:10.1139/v75-314

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The microwave spectra of glycidoland its deuterated (—OD) form have been studied in the range 8–40 GHz. The rotational (in MHz) and centrifugal distortion constants (in kHz) of glycidol are:A = 10 347.87,B = 4102.36, C = 3781.95; ΔJ = 2.38, ΔJK = −311, ΔK = 5.2, δJ = 0.3159, δK = −9.76. The rotational constants and distortion constants of glycidol (OD) areA = 10 010.31,B = 4056.73, C = 3717.02; ΔJ = 2.53, ΔJK = 197, ΔK = 7.7,δJ = 0.3532,δK = −7.19. The dipole moment components of the normal molecule in Debye units are μa = 0.61, μb = 1.20, μc = 0.52, and the total dipole moment is 1.44 D.A structure is derived with the alcoholic hydrogen atom close (2.5 Å) to the ring oxygen. The structure and the absence of signs of free or hindered rotation, can be accounted for by hydrogen bonding between the proton and the ring oxygen.

ISSN:0008-4042    

DOI:10.1139/v75-315

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Equations are derived for the dielectric constant of porous adsorbent – adsorbate systems based on several geometrical models and taking account of both adsorbate molecular orientation and the special geometrical relationship which exists between adsorbed and substrate phases. Isotropic distributions of coated spheres, rods, disks, and their cavity counterparts are treated. Although the equations are based on the above idealized physical models, unlike many previous derivations, no additional intuitive postulates are involved. Furthermore, the equations are correct in the various limiting cases in which two of the three phases are absent, again in contrast with some earlier equations. Some implications of the equations are discussed, particularly as they apply to molecular orientation. The question of a break in the curve of composite dielectric constantvs. volume adsorbed at monolayer coverage is also investigated.

ISSN:0008-4042    

DOI:10.1139/v75-316

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

A dilatometer using a micrometer syringe to measure small changes in volume at constant pressure is described. Excess volumes determined for cyclohexane + benzene at 298.15 K are in reasonable agreement with values from the literature. Results are also reported for the excess volumes of mixtures of ethylbenzene with benzene, toluene, and the isomeric xylenes.

ISSN:0008-4042    

DOI:10.1139/v75-317

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The major reactions in methane containing traces of ethane were studied with a pulsed electron beam high ion source pressure mass spectrometer. The CH4: C2H6ratios were changed from 50:1 to 100 000:1 at reaction temperatures between 28–210 °C. The reaction 1: CH5+ + C2H6 = CH4 + C2H7+still proceeded from left to right even at the highest dilution ratios. Measurement of the C2H7+/CH5+ratio under these conditions leads to a lower limit of the proton affinity difference PA(C2H6)–PA(CH4) > 10 kcal/mol. This result is in agreement with measurements by Bohme.It was observed that C2H7+decomposes slowly at 30 °C. The decomposition becomes more rapid at higher temperature. Measurements of the temperature dependence of the thermal reaction 2: C2H7+ + CH4 = C2H5+ + H2 + CH4, and an Arrhenius plot ofk2led to the activation energyE2 = 10.5 kcal/mol and preexponential factorA2 = 8.3 × 10−8(cm3molecule−1s−1). AssumingE2 = ΔH2one obtains ΔHf(C2H7+) = 208.5 ± 2 kcal/mol and PA(C2H7+) = 137.4 ± 2 kcal/mol. This is close to the proton affinity PA(C2H7+) = 139 ± 2 kcal/mol that can be deduced from Bohme's results.At higher dilution ratios the ion C2H5+was observed to react not only with ethane but also with methane by reaction 6: C2H5+ + CH4 = C3H7+ + H2,k6 ≈ 1 × 10−14 cm3molecule−1s−1at 86 °C. The reaction has positive temperature dependenc

ISSN:0008-4042    

DOI:10.1139/v75-318

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Synthesis of 2-hydroxy-2,5,5-trimethyl-Δ3-1,3,4-oxadiazoline (3) is described. It decomposes readily in solution at moderate temperatures, forming nitrogen and isopropyl acetate. Evidence for a concerted, radical-chain, induced decomposition by attack at hydroxyl hydrogen includes trapping of 2-acetoxy-2-propyl radicals by nitrosobenzene and by alkenes, inhibition of decomposition by (C6H5)3SnH, and initiation of decomposition by 'stable' free radicals. The novel chain decomposition of3is attributed to a concerted mechanism, which brings the heats of formation of nitrogen and of a carbonyl group into play to lower the free energy of activation.Synthetic utility of3is discussed together with a general principle pointing to new reagents for radical-chain additions to unsaturated systems.

ISSN:0008-4042    

DOI:10.1139/v75-319

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

A series of 3-substituted-aminomethy1-3-hydroxy-3,4-dihydro-2H-1,5-benzodioxepins is described. Members of the series constitute a unique class of β-adrenergic stimulants and possess interesting bronchial dilator activity.

ISSN:0008-4042    

DOI:10.1139/v75-320

出版商:NRC Research Press    

年代:1975

数据来源: NRC