共查询到20条相似文献,搜索用时 31 毫秒
1.
Julia C. Tai 《Journal of computational chemistry》1981,2(2):161-167
Parameters for sulfoxides used in force field MM1 were modified to be incorporated into force field MM2. The conformations of ten alkyl sulfoxides were then calculated using MM2 with these new parameters. The alkyl groups used were methyl, ethyl, isopropyl, and t-butyl. It was found that of the many possible conformations for these compounds, only one or two stable conformers exist, and that the number of these conformers agrees with the number of reported S? O stretching frequencies in almost every case. No apparent correlation between the vibration frequency and the molecular structure was found. 相似文献
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Using tetra-alkylammonium halides dissolved in alkyl halides as reagents a variety of halogen exchange reactions can be carried out conveniently in high yield. In particular, it becomes practicable to use -CH2Cl as a protected equivalent of -CH2Br. 相似文献
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S.T. YoffeP.V. Petrovsky Ye.I. GoryunovT.V. Yershova M.I. Kabachnik 《Tetrahedron》1972,28(10):2783-2798
A number of substituted ethyl formylacetates and ethyl formylmethylphosphonates were synthesized and their enolization studied by NMR. The ethyl halogen-or cyan)-formylacetates and formylmethylphosphonates exhibited stable trans-enolic forms in solutions. Variation of groupings bonded to the CO or PO groups affect the chelating centre basicity. With higher basicity the cis-enolic form is stabilized, and vice versa. Intermolecular hydrogen bonding stabilizes the trans-enolic forms of compounds containing a phosphoryl group. 相似文献
6.
P. J. Busse R. A. Grigsby F. L. Kolar K. J. Irgolic 《Journal of mass spectrometry : JMS》1976,11(6):640-643
The mass spectra of several alkyl phenyl tellurides, C6H5TeR (R = CH3, CD3, C2H5, n-C3H7, i-C3H7 and n-C4H9) have been studied with special emphasis on the fragmentation patterns involving cleavage of the alkyl and aryl tellurium–carbon bonds. Each compound exhibited intense parent ions. The rearrangement ions [C6H6Te]+? and [C6H6]+? were found in the spectra of phenyl ethyl and higher tellurides. Two other rearrangement ions [HTe]+ and [C7H7]+ were observed in the spectrum of each compound. Examination of the mass spectrum of phenyl methyl-d3 telluride demonstrated that the [HTe]+ ions derive hydrogen from the phenyl group. 相似文献
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N.C. Deno Elizabeth J. Jedziniak Lauren A. Messer Michael D. Meyer Stephen G. Stroud Edward S. Tomezsko 《Tetrahedron》1977,33(19):2503-2508
A solution of 30% aqueous H2O2 in trifluoroacetic acid converts linear alkanes and cycloalkanes to an equilibrium mixture of secondary alcohols and their trifluoroacetates. There is no trace of further oxidation to ketones. Yields and conversions can be 70–90%, but are limited by elimination and epoxidation to form vicinal glycols. Linear alkyl chains are also hydroxylated in good yields with selectivity for introducing the alcohol group remote from electronegative substituents. The active reagent is trifluoroperoxyacetic acid, and it is effective in the presence of 4–10% water. When tertiary hydrogens are present, the oxidations are more complex. 相似文献
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Marcia C. Blanchette John L. Holmes F. P. Lossing 《Journal of mass spectrometry : JMS》1989,24(8):673-678
The energetics of olefin loss from ionized alkyl phenyl ethers have been determined by ionization and appearance energy measurements. It is concluded that the reaction is governed by one or more of three features: (i) the strength of the bond between the phenoxy radical and the alkyl ion; (ii) the ease of isomerization of the alkyl ions, chiefly by H-shifts therein, and (iii) the strength of the C? H bond (primary, secondary and tertiary) involved in the H transfer to oxygen which precedes the olefin loss. The possible participation in the reaction of distonic ions and proton bound radical-molecule pairs is also discussed. 相似文献
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The HRP mass spectra of some alkyl isocyanides (R? NC in which R equals CH3, C2H5, n-C3H7, n-C4H9 and t-C4H9) and two methyl branched alkyl cyanides (R? CN in which R equals i-C3H7 and t-C4H9) have been studied. Using metastable ion transitions and appearance potentials, the fragmentation patterns and spectral characteristics of the isocyanides can be given. A comparison has been made with the mass spectral data of the corresponding cyanides. Although the mass spectra of alkyl cyanides and isocyanides show close relationship, evidence could be obtained that this resemblance is not caused by rearrangement of the isocyanide into cyanide molecules. The main difference between the spectra of both compounds is caused by the strength of the α-bond, being weaker in the case of the isocyanides. The abundance of ions formed by α-bond cleavage decreases with increasing size of the alkyl group. 相似文献
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László Seres Miklós G?rgényi Tamás K?rtvélyesi ágnes Nacsa 《Reaction Kinetics and Catalysis Letters》1992,48(2):635-639
In contrast with expectations based upon simple collision theory, reactions of alkyl radicals with substituted allyl radicals yield cross-combination ratios of =2. Reactions of CH
3
\
with some C5 radicals give >2, in accordance with theory.
, =2. CH3 \ C5 >2, .相似文献
14.
Yu. N. Polivin V. V. Yurechko T. P. Vishnyakova E. A. Ageev 《Russian Chemical Bulletin》1990,39(5):1050-1051
A study was carried out on the reaction of potassium cyanamide with normal alkyl bromides in 2-propanol, methanol, and dimethylformamide in order to obtain dialkylcyanamides. A virtually quantitative yield of dialkylcyanamides is achieved in dimethyl formamide.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1167–1169, May, 1990. 相似文献
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Dipole moments of several alkyl vinyl and alkyl propenyl ethers have been determined by the Halverstadt-Kumler method in benzene solution at 293 K. The μ values depend on the bulkiness of the alkyl group present. In the alkyl vinyl ether series, a part of the varying μ values may be ascribed to changes in molecular geometry with varying bulkiness of the alkyl group. Other factors are clearly involved, since even in the alkyl (Z)-propenyl ether series μ values depend significantly on the alkyl group, although the geometry of the molecules remains essentially constant throughout the series. In the latter series, the total dipole moment is linearly related to the Taft's σ*-values of the alkyl groups:μ/D=?(1.17±0.15)σ*+(1.29±0.03). This suggests that the variation of μ with the alkyl radical follows from the changing polar character of the alkyl groups, which leads to changes in the value of the group moment μro. 相似文献
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Silvestri MA Miles D Rothwell AP Wood KV Cushman M 《Rapid communications in mass spectrometry : RCM》2003,17(15):1703-1708
Electrospray ionization (ESI) mass spectrometry was employed to obtain both molecular weight confirmation and structural information for a series of novel alkenyldiarylmethane (ADAM) analogs. The mass spectral data were intended for use during the structure elucidation of ester hydrolysis products formed during an in vitro metabolism study of a series of novel ADAM analogs. The data on the precursor molecules show the presence of the molecular ion peak, [M+H](+), as well as a peak consistent with the hydrolysis product of the original ester ([MH-ROH+H(2)O](+)). However, chemical ionization mass spectrometry, elemental analysis and (1)H NMR data indicated the presence of only the intact diester compounds, suggesting that the formation of the hydrolysis product was an instrumental artifact, i.e., in-beam hydrolysis during ESI or a result of longer ion residence times of the ion trap mass analyzer. 相似文献
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V. N. Emel’yanenko O. V. Krol’ R. M. Varushchenko A. I. Druzhinina S. P. Verevkin 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2010,84(7):1089-1097
The heat capacity of iso-butylferrocene C5H5FeC5H4-C4H9-i was measured over the temperature range 7–372 K in an adiabatic vacuum calorimeter. Substance purity and the thermodynamic
characteristics of fusion (temperature, enthalpy, and entropy) were determined. Saturated vapor pressures and the enthalpies
of vaporization of n-propylferrocene C5H5FeC5H4-C3H7-n, propionylferrocene C5H5FeC5H4-COC2H5, and iso-butylferrocene were measured by the dynamic method of substance transfer in an inert gas flow. The entropy, enthalpy, and
Gibbs energy of the substances in the ideal gas state at 298.15 K were calculated. The thermodynamic values obtained in this
work and reported in the literature for ferrocene alkyl and acyl derivatives were critically analyzed. The mutual consistency
of the data on both homologous series was checked. 相似文献
20.
A series of alkyl lithium reagents has been found to react with hexafluoropropene oxide in the presence of ether to give carbinols of the type CF3CFRCR2OH. Butyllithium in hexane reacts “abnormally” to give the carbinol CF3C(OH) BuCF2Bu. Mechanisms to account for these difference are presented. 相似文献