摘要:

The title compounds thermolyse at 50–100 °C in a variety of solvents via two (and only two) competing unimolecular pathways, one producing a diazoalkane and carbon dioxide, the other a ketone, carbon monoxide, and dinitrogen. Diazoalkane formation is favoured by polar solvents and electron-donating substituents, with a Hammett ρ of −1.93 for sevenp-substituted 5-methyl-5-phenyloxadiazolinones. Moderate solvent polarity effects, secondary kinetic isotope effects (2.1 ± 0.3% per D for2b-d6), the Hammett ρ, and Frontier Molecular Orbital Theory, all support concerted diazoalkane formation through a transition state with nonsynchronous bond rupture.Neither decomposition mode shows any correlation with Taft steric parameters,Es, and ketone formation does not correlate with inductive parameters. The enthalpy change during the exothermic three piece fragmentation was calculated to be only −30 ± 2 kcal mol−1, precluding chemiluminescence. A vigorous search for intermediates by esr, ms, CIDNP, trapping, and racemization experiments leads to the conclusion that ketone formation must also be concerted.A new oxidation procedure using lead tetraacetate in the presence of five equivalents of trifluoroacetic acid was useful in the synthesis of oxadiazolinones from ketone semicarbazones which would not cyclize under normal LTA oxidation conditions.

ISSN:0008-4042    

DOI:10.1139/v79-435

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The azido ketones4c–eand10a–dreacted with triphenylphosphine under mild conditions to give the benzo-1,4-diazepin-2-ones7c–eand the 1,2-dihydropyrazin-2-ones12a–d, respectively.The electron impact induced fragmentation of the 1,5-disubstituted-1,2-dihydropyrazin-2-ones was shown to occur by extensive skeletal rearrangement. The 1,5-diaryl derivatives12a–cfragmented via 1,4-diarylimidazole species produced by the expulsion of CO from the molecular ion. In contrast, the 1-cyclohexyl-5-phenyl derivative12dfragmented almost entirely via a 2-hydroxypyrazine intermediate derived from the molecular ion by McLafferty cleavage.

ISSN:0008-4042    

DOI:10.1139/v79-436

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The phase transformations occurring in K2Cr2O7have been examined by differential thermal analysis (DTA), differential scanning calorimetry (DSC), specific heat measurements, electrical conductivity technique, and X-ray diffractometry. The results show that the polymorphic behavior of K2Cr2O7is very sensitive to the thermal and preparative history of the sample.

ISSN:0008-4042    

DOI:10.1139/v79-437

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Complex formation between pentachlorophenol-OD (PCP-OD) and acetone and acetone-d6in CCl4solution has been studied. Digitized infrared spectra in the O—D stretching region ν(OD) of PCP-OD and the C—O stretching region ν(CO) of acetone have been recorded from solutions of various concentrations. The present results are compared with previous work on complex formation between PCP and the same acceptor molecules. In the ν(OD) region, factor analysis (principal component analysis) and a concentration study of the areas of the resolved band components suggest that two (1:1) complexes occur in solution. The equilibrium constant obtained for one of the complexes shows an isotope effect due to deuteration of the proton donor. In the ν(CO) region, only one band due to complexed species was resolved. Equilibrium constants calculated using the results from the ν(OD) and ν(CO) regions are in good agreement with each other.

ISSN:0008-4042    

DOI:10.1139/v79-438

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

PF3and CO react with CuAsF6in SO2solution to form 1:1 addition compounds, the vibrational spectra of which are consistent with the formulations [CuPF3]+[AsF6]−and [CuCO]+[AsF6]−. The latter has a v[CO] stretch at 2180 ± 5 cm−1, the highest yet observed for a monocarbonyl.

ISSN:0008-4042    

DOI:10.1139/v79-439

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The density normalized mobilities μnat low electric field strengths in the low density gases fall in the ordertrans-2- > cis-2- > 1- > isobutene. The respective values in the saturated vapors at 297 ± 1 K were 10.7, 4.4, 3.8, and 1.84 (1022 molecules/cm V s). The scattering cross section σvhas a Ramsauer–Townsend-like minimum at an electron energy of 0.085 eV intrans-2-butene, 0.13 eV incis-2-butene, 0.12 eV in 1-butene, and 0.16 eV in isobutene. The mobilities in the last three isomers increase with increasing temperature (300–500 K) and field strength. Temperature and field effects were smaller intrans-2-butene. The ratio of the field effect threshold drift velocity to the speed of sound in the low density gas is 14, 19, 20, and > 50 in iso-, 1-,cis-2-, andtrans-2-butene, respectively, at 297 K. The electrons are de-energized mainly by inelastic collisions. Quasilocalization occurs to a similar extent in each of the isomers at densitiesand temperatures near the coexistence curve. Quasilocalization is characterized by large, negative values of ΔHand ΔS, and a small value of ΔGover a small temperature range.

ISSN:0008-4042    

DOI:10.1139/v79-440

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Two equivalents of the title compound (1) react with one equivalent of primary alcohols to give good yields of nitrogen and 1-alkoxycarbonyl-2-N-phenylcarbamoyl-4-phenyl-1,2,4-triazolidine-3,5-di ones (3). With secondary alcohols or benzyl alcohol the major products are the ketone or benzaldehyde, while3are minor products. The latter can, however, be made the major products if pyridine is used to catalyze the reaction. Compound3adissociates on heating or in pyridine solution into the 1-methoxycarbonyltriazolidinedione4.If alcohols are absent1is converted by pyridine or other tertiary amines into nitrogen and the bicyclic compound9; if diethyl azodicarboxylate is present in the reaction compound13can be trapped.Primary and secondary amines react very rapidly with1to give nitrogen and complex products. It is likely that these are 1,2-dicarbamoyl-4-phenyltriazolidine diones, analogous to3, and that they are very prone to dissociate in solution.

ISSN:0008-4042    

DOI:10.1139/v79-441

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

1,3-Diaryl-2-propen-1-ones1reacted with thiourea in the presence of sodium ethoxide to give 4,6-diaryl-3,4-dihydropyrimidine-2(1H)thiones5which upon dehydrogenation with 3 mol of ethanolic sodium ethoxide yielded the corresponding 4,6-diarylpyrimidine-2(1H)thiones9. TheN-acetyl derivatives of the former thiones were prepared. Infrared, nuclear magnetic resonance, and ultraviolet spectral data of the above compounds were tabulated and discussed.

ISSN:0008-4042    

DOI:10.1139/v79-442

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The AlCl3-promoted reaction of methyl 2,5-dimethylpyrrole-1-carboxylate1with dimethyl acetylenedicarboxylate affords under certain conditions a low yield of 2,5-dimethyl-2-tricarbomethoxyvinyl-2H-pyrrole3. The structure of the latter was established on the basis of detailed1H and13C nmr studies, and confirmed by conversion to dimethyl 5-methyl-5-(3-oxobutyl)-3-pyrrolin-2-one-3,4-dicarboxylate4.

ISSN:0008-4042    

DOI:10.1139/v79-443

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

A new semiquantitative method has been developed for measuring the relative acidities of methanol, ethanol, isopropyl alcohol, andtert-butyl alcohol in mixed hydroxylic solvents. A solution of the alkoxides of two alcohols in an excess of the two alcohols is allowed to react withn-butyl bromide to form a mixture of two ethers. The composition of the ether mixture is a measure of the "competitive reactivity" of thetwo alkoxides. This can be measured directly, and in theory can be factored into two components: the relative nucleophilicity and the relative basicity of the two alkoxides. Relative nucleophilicities are determined by using solutions in which phenol is one component. Knowing the competitive reactivities and nucleophilicities, the relative acidities of methanol, ethanol, isopropyl alcohol, andtert-butyl alcohol in alcoholic media are shown to be 4.4, 1.0, 0.24, and 0.21, respectively. The relative nucleophilicities of hydroxide, methoxide, ethoxide, isopropoxide,tert-butoxide, phenoxide, andm-cresoxide are 0.08, 0.82, 1.0, 0.4, 0.04, 0.46, and 0.57 respectively.

ISSN:0008-4042    

DOI:10.1139/v79-444

出版商:NRC Research Press    

年代:1979

数据来源: NRC