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Showing 1 to 20 of 68 for “"Carbonyl group"”.
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Ripening Kinetics of Iron Sulfides in the Presence/Absence of a Carbonyl Group
… suppress pyrite production in the presence of carbonyls. Samples of iron sulfides were collected at predetermined intervals and analyzed by powder XRD. Two distinct ripening pathways were found: if a carbonyl (formaldehyde) was present, mackinawite ripened to greigite. If a carbonyl was absent, …
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The importance of the antiperiplanar effect in the nucleophilic addition of hydride to a carbonyl group.
… solvent dependence with the $\alpha$-methylthio group existing mainly in its axial conformer (n$\rm \sb{a}$ = 0.94) while the $\alpha$-methoxy group shows only a marginal preference in the same solvent (n$\rm \sb{a}$ = 0.56). Employing these results and those known for the $\alpha$-halo …
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Thermochemical properties of c3 to c5 unsaturated carbonyl alkenes: enthalpies of formation, entropy, heat capacity, bond enthalpy
[alpha],[beta] and [alpha]-[gamma] unsaturated carbonyl compounds are important classes of carbonyl compounds with the general structure R-(O=C)-C[alpha]=C[beta]-R' and R-(O=C[gamma])-C[beta]-C[alpha]=C[beta]-R'. These compounds are utilized in industry and are also produced as intermediates of …
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Kinetics and Mechanism of Syn, Alpha' Lithiation of Tertiary Benzamides
… the carbon adjacent to nitrogen and syn to the carbonyl group. Evidence obtained by nuclear magnetic reso- nance, freezing point depression and stopped-flow infrared spectros- copy indicates the reaction proceeds with rapid initial formation of tetrameric complexes followed by rate determining …
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Intramolecular Reactions of Trivalent Phosphorus and Carbonyl Functions
… stable tricyclic phosphoranes in cases where the carbonyl function is an aldehyde, trifluoroacetophenone, or diaryl ketone. A methyl imine function may also participate in such a reaction. Oxidative cyclization does not occur where the carbonyl group in the phosphonous diester is an ester or a …
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Dioxirane-mediated epoxidation of alkenes: The development of catalytic and asymmetric protocols
… using phase transfer catalysts bearing a carbonyl group. Optimal epoxidation conditions employ 10 mol % of 1-dodecyl-1-methyl-4-oxopiperidinium trifluoromethanesulfonate (9d$\sp+$OTf$\sp-)$ in a $\rm CH\sb2Cl\sb2$/pH $7.5{-}8.0$ biphase using potassium monoperoxosulfate (Oxone) as the …
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The effects of structural changes on the formation of urea adducts of esters
… consisted of changing the position of the carbonyl group in a series of straight chain twenty-carbon esters.</p>
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The urea adducts of certain esters containing twenty carbons
… effect of the position in the molecule of the carbonyl group in the formation of urea adducts with a series of twenty carbon esters.</p>
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The Oximes of 1-(3-Methoxy-4-Agetoxyphenyl)-2, 6-Dicarbethoxycyclohex-Anedione-3,5 and their Derivatives
The oximes represent an important group of compounds in the research field of organic chemistry. They can "be prepared either by the reaction of the carbonyl group with hydroxylamine or by the reaction of nitrous acid or nitrous acid esters on compounds containing reactive methylene groups. These …
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Synthetic and Mechanistic Studies of Carbamate-Directed Lithiation Reactions: (1) Assymetric Deprotonation of N-Boc Indolines. (2) the Relationship Between Reactivity and Directing Group Orientation
… and the lithium. Chelation of the carbamate carbonyl oxygen to the lithium in $\alpha$-lithio carbamates appears to influence their thermodynamic stability. These studies demonstrate that the position of the carbonyl group with respect to the proton removed in a carbamate-directed lithiation …
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Nickel-catalyzed cross-couplings of unactivated secondary and tertiary alkyl halides and photoinduced copper-mediated asymmetric C-N cross-couplings
… 1.1, asymmetric [gamma]-alkylation relative to a carbonyl group is achieved via the stereoconvergent cross-coupling of racemic secondary [gamma]-chloroamides with primary alkylboranes. Section 1.2 describes the first Suzuki carbon-carbon bond-forming reaction using tertiary alkyl halides as …
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Halo Enol Lactones as Enzyme-Activated Irreversible Inhibitors of Alpha-Chymotrypsin: I. The Effect of Lactone Substitution Pattern. Ii. Alpha - Amino-Functionalized Lactones
Halo enol lactones with a phenyl group situated (beta) or (gamma) to the lactone carbonyl group were prepared to compare their effectiveness as enzyme-activated irreversible (suicide) inhibitors for (alpha)-chymotrypsin with the activities of the corresponding (alpha)-substituted lactones. The …
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Characterization of a Catechol-Type Siderophore and the Detection of a Possible Outer Membrane Receptor Protein from <em>Rhizobium leguminosarum</em> strain IARI 312.
… siderophores chelate ferric iron via hydroxyl groups, and hydroxamate-type siderophores chelate ferric iron via a carbonyl group with an adjacent nitrogen. Rhizobia fix atmospheric nitrogen symbiotically in leguminous plants using the iron-containing enzyme nitrogenase. To satisfy their iron …
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An excursion into the synthesis of novel flavanones
… to the poor electrophilicity of the ketone carbonyl group in the enamine formation step because of the ortho electron-releasing phenolic hydroxyl group. For increasing the electrophilicity, the approach was changed to using a Knoevenagel condensation reaction between an activated β-ketoester …
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Isolation and Partial Characterization of the Toxic Substance from EREMOCARPUS SETIGERUS BENTH
… or a highly symmetrical secondary hydroxyl group and carbonyl group. The functional group tests also indicate the presence of ketone, ester, enol and isolated double bond groups. We believe that the enol form is attributed to the conjugation of the ketone and the ester groups at a β-carbon …
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The integration of computational and spectroscopic information for hydrogen bonded systems
… possible isomers; HC1 may bond to the nitrile group, to the carbonyl group <i>cis</i> to the nitrile or to the carbonyl group <i>trans</i> to the nitrile. Calculated values of hydrogen bond energy; harmonic HC1, CO and CN stretching modes; hydrogen bond lengths and other associated lengths and …
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Design and synthesis of potential inhibitors of enzymes involved in the biosynthesis and utilisation of mycothiol
… reaction that took place during an N-tert-butoxycarbonyl deprotection step. However, this unexpected result led to the discovery of a new synthetic route to benzo[g]indoles and benzo[h]quinolines. This route differs from traditional quinoline and indole syntheses in that the aromatic C-N bond is …
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Steroid 2,4-Dinitrophenylhydrazones: their preparation, separation, and characterization
… could be classified into four well defined groups on the basis of their ultraviolet spectra and that this classification could be correlated with the structures of the DNPH's. Within each group the compounds were similar to each other with respect to their melting points, color, solubilities …
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Theoretical and experimental studies of slowly deacylating alpha-chymotrypsin acyl enzymes
… other non-bonded interactions pulls the ester carbonyl group out of the oxyanion binding hole. This distortion of geometry raises the energy of activation for hydrolysis of the acyl enzyme by providing little stabilization of the negative charge that develops during the rate determining process …
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