摘要:

Dimethyl ether was pyrolyzed in a flow System at 788, 856, and 935 K and 38–401 Torr. Measurement of the yields of CH4and C2H6and of either H2or CO enabled calculation of high pressure limiting values of the rate constant quotientk9k6−1/2, where reaction 9 isand reaction 6 is the recombination of two methyl radicals. Including literature data from 357–1005 K, the Arrhenius plot for this quotient is a curve.

ISSN:0008-4042    

DOI:10.1139/v78-217

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

A series of nickel(II) and copper(II) complexes of the title ligand are reported which appear to exhibit predominantly pseudo-octahedral structures in the solid state. Anion bridged dimeric structures are proposed for both nickel and copper; [Ni2(NTB)2X2]Y2 (X = Y= Cl, Br; X = Cl, Br, NCS; Y = BPh4), [Cu2(NTB)2X2]X2•2H2O (X = Cl, Br). The other octahedral derivatives appear to be monomeric; (Ni(NTB)X2] (X = NO3, NCS), [Ni(NTB)-(H2O)X]Y (X = NCS, Y = BPh4; X = CH3CN, Y = (ClO4)2), [Ni(NTB)(H2O)2]X2•2H2O (X = ClO4, BF4), [Cu(NTB)(NO3)2]•H2O. Five-coordinate derivatives were uncommon and in the case of three copper complexes trigonalbipyramidal structures are suggested in the solid state; [Cu(NTB)CI]BPh4, [Cu(NTB)(H2O)]X2•nH2O (X = BF4,n = 0; X = ClO4,n = 1). In acetone solution ail the copper complexes appear to be five-coordinate. Electron spin resonance data confirm trigonalbipyramidal solution structures and indicatewith very small values of(60 − 80 × 10−4 cm−1).

ISSN:0008-4042    

DOI:10.1139/v78-218

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

CNDO/2 Frontier molecular orbital densities, ionization potentials (IP's), and electronic transition energies were calculated for the title compound (2b) and the 5,5-diprotio (2a), and 5,5-difluoro (2d) analogs. Bond lengths and angles were not optimized but rather taken from a crystal structure of the 2-imino System 3, with an assumed carbonyl bond length ofRco = 1.19 Å. This value is supported by a high infrared stretching frequency (1835 cm−1), X-ray crystal data of 3, and the effect ofRcovariation on calculated IP's. The first three bands of the photoelectron spectrum of2bwere assigned as nN−(10.20 eV), π1(11.52eV), and nco(13.26 eV) (vertical IP's). This unusually large ncoIP is attributed to an inductive effect of the neighbouring strongly electron withdrawing azo group. The IP's obtained by CNDO/2 calculation (12.81, 13.37, and 15.15) are 1.5 to 2.5 eV higher than the experimental values, well within the predictive capability of the method, establishing that this theoretical treatment gives a good representation of the MO's of2b.

ISSN:0008-4042    

DOI:10.1139/v78-219

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The rate of formation of1from horseradish peroxidase and hydrogen peroxide is investigated as a function of pHbetween pH9.5and 11.5. For pHvalues smaller than 10, the rate depends linearly on hydrogen peroxide concentration, whereas between pH10 and 11.5, the rate displays saturation kinetics. Evidence is presented for the formation of an intermediate complex before compound1formation. Two parameters were measured as a function of pH:kapp, the apparent rate constant for compound1formation, andkapp, the dissociation rate constant of the intermediate complex to1. A third parameter,kapp, similar to a dissociation constant for the reaction was deduced from the two rate constants. The apparent rate constantkappis pHindependent for pHvalues < 9.5 and is directly affected by ionization of only one group on the native enzyme with a pKof 11. The pHdependances ofkdandKapprequire a minimum of two ionizations. One corresponds to a group on the native enzyme which ionizes at a pHlower than that of the present study, the second corresponds to the ionizable group with pKof 11. For cyanide binding to horseradish peroxidase over the same pHinterval, saturation kinetics were not observed, yet the pHprofile forkappexactly parallels that for formation of1(when corrected for the effect of the ionization of HCN) and shows an inflection at the same pHvalue.

ISSN:0008-4042    

DOI:10.1139/v78-220

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The synthesis of 7β-(-2′-thienylacetamido)-3-acetoxymethyl-Δ3-O-2-isocepheni-4-carboxylic acid (17) is described. Thus treatment of enol mesylate 3aor triflate 3bwith triethylamine gave the allene4which gave the diiodide upon treatment with iodine. The diiodide gave benzyl 7β-azido-3-acetoxymethyl-Δ3-O-2-isocephem-4-carboxylate (12) on treatment with potassium acetate in DMF. Hydrogenolysis of12gave the amino acid16which was converted to17upon treatment with 2-thienylacetyl chloride. Resolution of17into its optical antipodes was carried out. The antibiotic activities of racemic17and each antipode is compared to that of cephalothin. Antibiotic activity was found to reside in the dextrorotatory isomer.

ISSN:0008-4042    

DOI:10.1139/v78-221

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The equilibration of the α,α -diniethyl derivatives of bicyclo[2.2.2]octenone, bicyclo[3.2.1]-oct-2-en-6-one, and its Δ3isomer has been examined at 155 and 185 °C intert-BuO−/tert-BuOH. Using2Hmr spectroscopy the rates and stereoselectivity of hydrogen–deuterium exchange in each of these ketones have been determined for equilibrations withtert-BuOD as solvent. The relative reactivities for exchange at the allylic and vinylic sites compared to the analogous results for the corresponding olefins reveal a significant activating effect of the carbonyl group. Comparison of the data with those for the corresponding saturated ketones shows that the double bond enhances the rate of isomerization appreciably and increases the bias of the equilibrium toward the [3.2.1] skeleton.

ISSN:0008-4042    

DOI:10.1139/v78-222

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Nitration of 2-chloro-1,3,5-trimethylbenzene in acetic anhydride gives thecisandtransisomers of 4-chloro-1,3,5-trimethyl-4-nitrocyclohexa-2,5-dienyl acetate (1, 21%), thecisandtransisomers of 3-chloro-2,4,6-trimethyl-4-nitrocyclohexa-2,5-dienyl acetate (2, 6%), and 2-chloro-1,3,5-trimethyl-4-nitrobenzene (73%). Diene1reacts with acidified aqueous acetone to form the corresponding dienol, acidified methanol to form the methyl ether, and hydrogen chloride to form the corresponding chloride. In acetic acid a mixture of 4-chloro-3,5-dimethyl-benzyl derivatives and 3-chloro-2,4,6-trimethylphenyl acetate are formed. In trifluoroacetic acid – trifluoroacetic anhydride and also in boron trifluoride etherate, 2-chloro-1,3,5-trimethyl-4-nitrobenzene is the predominant product. Diene2on reaction with acetic acid, acidified methanol, trifluoroacetic acid – trifluoroacetic anhydride, and boron trifluoride etherate gives 3-chloro-2,4,6-trimethylphenyl acetate. Some 2-chloro-4-nitromesitylene is obtained in trifluoromethanesulfonic acid. Diene2also gives the acetate on standing at ambient temperature or at −20 °C, and on pyrolysis. Diene1gives 4-chloro-3,5-dimethylphenylnitromethane on standing at ambient temperature or at −20 °C but a mixture of 2-chloro-1,3,5-trimethyl-4-nitrobenzene, chloromesitylene, and 3-chloro-2,4,6-trimethylphenyl acetate on pyrolysis.

ISSN:0008-4042    

DOI:10.1139/v78-223

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

1,2,4,5-Tetraphenyl-3,6-dicarbomethoxycyclohexa-1,4-diene crystallizes in the monoclinic space groupI2/a(a non-standard setting of C2/c) witha = 20.052(2),b = 5.756(1),c = 22.782(2) Å, β = 95.73(1)°, and Z = 4. 1,2-Dicarbomethoxy-4,5-dimethylcyclohexa-1,4-diene crystallizes in the orthorhombic space groupPbcawitha = 25.627(2),b = 11.240(1),c = 8.342(1) Å, and Z = 8. Both structures were solved by direct methods and refined by full matrix least-squares techniques toR = 0.040 andR = 0.036, respectively. Carbon–carbon double bond lengths are similar in the two compounds (1.326 and 1.333 Å, respectively), but the single bond lengths are significantly longer in l,2,4,5-tetraphenyl-3,6-dicarbomethoxycyclohexa-1,4-diene (1.518 Å) compared with the 1.493 Å average found in 1,2-dicarbomethoxy-4,5-dimethyl- cyclohexa-1,4-diene. This and the fact that there are also small deviations from planarity in the former compound are thought to be due to the presence of substituents on the methylenic carbon atoms.

ISSN:0008-4042    

DOI:10.1139/v78-224

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

1,2,4,5-Tetraphenyl-3,6-dicarbornethoxytricyclo[3.1.0.02,4]hexane crystallizes in the monoclinic space group P21/cwitha = 10.044(4),b = 9.500(2),c = 14.172(4) Å, β = 104.38(2)°, andZ = 2. Using 1032 unique reflections withI > 3σ(I), the structural data were refined by full matrix least-squares techniques toR = 0.038. The molecule was found to be in theanti-configuration. All bond lengths within the highly strained central tricyclic framework were equal within experimental error and average 1.531 Å.

ISSN:0008-4042    

DOI:10.1139/v78-225

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Se lective thioketalization of a mixture of keto esters5and6resulted in the exclusive formation of thioketal7and complete recovery of keto ester6. Lithium aluminum hydride reduction of thioketal7followed by Moffatt oxidation of the resulting alcohol8gave aldehyde10which on treatment with a mixture ofcis- andtrans-1-propenyl magnesium bromide affordedtrans- alcohol11and itscisisomer12. Manganese dioxide oxidation of alcohol11followed by desulfurization gavetransα-damascone (3). Similarly, alcohol12was converted tocis-α-damascone (4).

ISSN:0008-4042    

DOI:10.1139/v78-226

出版商:NRC Research Press    

年代:1978

数据来源: NRC