摘要:

The aquation of Cr(NH3)5NO32+in acidic solutions yields not only Cr(NH3)5OH23+(33%) but also more highly aquated species includingcis-Cr(NH3)4(OH2)23+and Cr(NH3)3(OH2)33+. In 0.1 MHClO4, several successive reactions of comparable rates are involved, but at pH6 only the two competing initial reactions producing Cr(NH3)5OH2+andcis-Cr(NH3)4(OH)NO3+are rate-controlling, so that the overall reaction rate is first-order in substrate with the apparent parameterskA = 2.4 × 10−3 s−1(25°), ΔHA* = 20.4 kcal mol−1, and ΔSA* = −2.1 cal deg−1mol−1. In alkaline solutions, the pseudo-first-order rate of hydrolysis at a given [OH−] is governed bykobs = kA + kOH[OH−], withkOH = 1.1 × 10−2 M−1s−1(25°), ΔHOH* = 25.2 kcal mol−1, and ΔSOH* = 17.0 cal deg−1mol−1. The path characterized bykOHleads exclusively to Cr(NH3)5OH2+. In both aquation and base hydrolysis, it is the Cr—ONO2bond that is broken. The production of more highly aquated species in the aquation reactions is attributed to transient chelation of NO3−at the expense of a ligandcisto it. The evidence for this mechanism, and for its operation when oxyanions other than nitrate are coordinated to Cr(III), is reviewed.

ISSN:0008-4042    

DOI:10.1139/v74-083

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The reactions of 1-chloropropane (1) and 1-chloro-2-methylpropane (2) with clean, polycrystalline films of the metals Ti through Cu were studied at ambient and elevated temperatures. At ambient temperature all of the metals exhibited a complex pattern of behavior. Titanium was uniquely different from other metals in that no catalytic hydrogenation of product olefin by product hydrogen was observed.At elevated temperatures the two reactants exhibited the same dichotomy as previously reported for titanium in that2was catalytically dehydrochlorinated by all metals, whilst1underwent non-catalytic dehydrochlorination. Except in the cases of Ti and Mn, the halide deposited by reaction of1with the metal surfaces provided an effective diffusion barrier to further reaction. It is suggested that the rate-controlling step for both Ti and Mn in reactions with1is transport of metal atoms from the pure metal into the halide surface layer.

ISSN:0008-4042    

DOI:10.1139/v74-084

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Ab initio calculations have been performed on a series of molecules HCOX, where X=CH3, NH2, OH, F, H, and also on the corresponding oxygen protonated cations. Rotational studies show the incoming proton to be trans to the substituent X except in formyl fluoride, where internal hydrogen bonding stabilizes the cis isomer. The geometries of the fluoro- and amino-substituted cations have been optimized along with that of oxygen protonated ketene. Proton affinities are found to be very dependent on substituents with the order of basicity beingan order which closely follows the negative charge on the oxygen. Plots of the computed charge on the carbon atoms against the core binding energy are different for the cations and neutral compounds but can be made to fall on the same line by correcting the binding energy using "the charge potential model" for the K-shell electron which is removed.

ISSN:0008-4042    

DOI:10.1139/v74-085

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Thetert-butylsulfinyl radical, (CH3)3CSO•, can be prepared directly in the cavity of an e.p.r. spectrometer by photolysis of di-tert-butyl peroxide in a solution oftert-butylsulfenic acid in toluene or isopentane at low temperatures (−40° to−100°). The e.s.r. spectrum consists of a rather broad singlet (ΔHmis ∼ 1.9 G) with the field center atg = 2.0106.This radical undergoes self-reaction by a bimolecular process and a 2.5 × 10−7 Msolution has a half-life of 0.07 s at −100 °C. It is, therefore, much shorter-lived than the iso-structural tert-butylperoxy radical, (CH3)3COO•.

ISSN:0008-4042    

DOI:10.1139/v74-086

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The vapor pressures over benz[a]anthracene (B[a]A), benzo[a]pyrene (B[a]P), benzo[e]pyrene (B[e]P), benzo[ghi]perylene (B[ghi]P), and coronene have been measured using the Knudsen effusion weight loss method. The parametersAandBin the equation log10[p(atm)] = -(A/T) + B and the enthalpies of sublimation in kcal mol−1derived therefrom are respectively: B[a]A, 5925 ± 36, 10.045 ± 0.099, 27.12 ± 0.54; B[a]P, 6181 ± 32, 9.601 ± 0.083, 28.29 ± 0.51; B[e]P, 6220 ± 33, 9.736 ± 0.085, 28.46 ± 0.55; B[ghi]P, 6674 ± 40, 9.519 ± 0.093, 30.54 ± 0.55; coronene, 7100 ± 69, 9.110 ± 0.149, 32.49 ± 0.55. The errors shown for theAand B values are standard deviations and for the enthalpies of sublimation are estimates of total probable error.

ISSN:0008-4042    

DOI:10.1139/v74-087

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Asymmetry in the Mössbauer spectra of Te(II) thiourea complexes is shown to be due predominantly, if not exclusively, to single crystal orientation effects. The asymmetry in TeTu4Cl2•2H2O is consistent with a negative sign for the nuclear quadrupole moment of theexcited state in125Te.

ISSN:0008-4042    

DOI:10.1139/v74-088

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Eight newcis-methylplatinum(II) derivatives of the typeDIARSPt(CH3)X (DIARSabbreviateso-phenylenebis(dimethylarsine), where X is an anionic substituent, and [DIARSPt(CH3)L]+PF6−, where L is a neutral ligand, have been prepared. Data derived from the13C n.m.r. spectra of these complexes are discussed and compared with data derived from the1H n.m.r. spectra of the complexes. Comparisons with the13C n.m.r. parameters obtained from related series oftrans-methylplatinum(II) derivatives reveal marked differences between the n.m.r.cis- andtrans-influences. It appears that the n.m.r.cis-influence may in part be related to a ligand's "steric bulk".

ISSN:0008-4042    

DOI:10.1139/v74-089

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Crystal field calculations for d3, d7square pyramidal complexes are carried out via the strong field formalism and in the limit of zero spin-orbit coupling. The field produced by the lone axial ligand is treated as an integral part of the crystal field potential. In the ionic model approximation the three crystal field parameters:Dq,Ds, andDt; depend markedly on the angle of distortion, β, defined as that portion of the La—M—Lbbond angle in excess of 90°. The square pyramidal d3symmetry eigenfunctions are constructed from the one-electron crystal field eigenfunctions. Spin is only implicitly included, but both types of doublet wavefunctions are identified. The crystal field matrix in parametric form is strictly diagonal, but Coulombic interactions connect states arising from different strong field configurations. Coulombic calculations are performed in terms of the Slater–Condon–Shortley parameters:F0,F2, andF4; then converted to the Racah parameters:A,B, andC, The complete (crystal field and Coulombic) perturbation matrices are used to interpret the spectroscopic properties of a strong field Co(II) square pyramidal complex. Both the symmetry and multiplicity of the ground state are dependent on β. An energy level diagram showing all doublets and quartets is calculated for β = 0°. Partial energy level diagrams are also given depicting behavior of the doublet and quartet states, individually, as functions of β. As β increases the crystal field bands shift to lower energy and become more clustered. Current experimental applications are also briefly cited.

ISSN:0008-4042    

DOI:10.1139/v74-090

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Aluminum trichloride can be intercalated in the lattice of graphite. This intercalate is a milder catalyst than AlCl3for the alkylation reactions and gives less polysubstituted reaction products.

ISSN:0008-4042    

DOI:10.1139/v74-091

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The primary deuterium isotope effect has been measured for the proton transfer reaction from di-(4-nitrophenyl)methane tot-butoxide ion in a solvent consisting of 10% v/v toluene int-butanol at a series of temperatures between 20 and 45 °C. The isotopic rate ratio,kH/kD, is 7.3 at 25 °C. The activation parameters showed an enthalpy of activation difference (ΔHD≠ − ΔHH≠) of onlyca. kcal mol−1and an entropy isotope effect (ΔSD≠ − ΔSH≠) of −2.4 cal mol−1deg−1. The latter indicates, according to the theory of Bell, that tunnelling of the proton through the energy barrier is unimportant in this reaction. This result is compared to other reactions in the literature, in which tunnelling has been postulated to occur.

ISSN:0008-4042    

DOI:10.1139/v74-092

出版商:NRC Research Press    

年代:1974

数据来源: NRC