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Methylene Protons (methylene + proton)
Selected AbstractsSynthesis and NMR spectral study of some t(3)-aryl- r(2),c(4)-bisethoxycarbonyl- t(5)-hydroxy- c(5)-methylcyclohexanonesMAGNETIC RESONANCE IN CHEMISTRY, Issue 5 2005K. Pandiarajan Abstract Six t(3)-aryl- r(2),c(4)-bisethoxycarbonyl- t(5)-hydroxy- c(5)-methylcyclohexanones (6,11) were synthesized by condensing ArCHO (Ar = Ph, p -O2NC6H4, p -CH3OC6H4, p -ClC6H4, m -O2NC6H4 and m -C6H5O6H4) with ethyl acetoacetate in the presence of methylamine and their 1H and 13C NMR spectra were recorded. 1H,1H COSY and NOESY spectra were recorded for 6 and 7 and also HSQC and HMBC spectra for 6 and 8. Elemental analysis was carried out for all compounds. The mass spectrum was recorded for 8. All analytical data are consistent with the proposed molecular formulae. Analysis of NMR spectral data suggests that these compounds largely adopt chair conformations with the hydroxyl group occupying an axial orientation and all the other substituents occupying equatorial orientations. Long-range coupling (2,3 Hz) between the OH proton and the axial methylene proton at C-6 is observed in 6, 7, 8 and 11. Copyright © 2005 John Wiley & Sons, Ltd. [source] Synthesis of biodegradable copolymers with low-toxicity zirconium compounds.JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 1 2006Abstract The results of the copolymerization of glycolide with cyclic trimethylene carbonate and 2,2-dimethyltrimethylene carbonate are described. The copolymerization was conducted in the presence of low-toxicity zirconium(IV) acetylacetonate as an initiator. With this kind of initiator, the composition of the comonomer units in the copolymer chains was assumed to be obtained with high efficiency. Despite significant differences in the comonomer reactivity, in copolymers containing comparable amounts of glycolidyl and carbonate sequences, highly randomized chain structures were observed. This effect resulted from strong intermolecular transesterification that proceeded during the studied copolymerization and caused glycolidyl microblock randomization. The assignment of the spectral NMR lines to appropriate comonomer sequences of polymeric chains was performed in the region of methylene protons of glycolidyl units in 1H NMR spectra of the copolymers and in the carbonyl region of carbon spectra. The equations were formulated for a detailed characterization of the obtained copolymer chains, the average lengths of the blocks, and the transesterification and randomization coefficients. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 98,114, 2006 [source] In situ Fourier transform near infrared spectroscopy monitoring of copper mediated living radical polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2004Vincent Darcos Abstract In situ Fourier transform near infrared (FTNIR) spectroscopy was successfully used to monitor monomer conversion during copper mediated living radical polymerization with N -(n -propyl)-2-pyridylmethanimine as a ligand. The conversion of vinyl protons in methacrylic monomers (methyl methacrylate, butyl methacrylate, and N -hydroxysuccinimide methacrylate) to methylene protons in the polymer was monitored with an inert fiber-optic probe. The monitoring of a poly(butyl methacrylate- b -methyl methacrylate- b -butyl methacrylate) triblock copolymer has also been reported with difunctional poly(methyl methacrylate) as a macroinitiator. In all cases FTNIR results correlated excellently with those obtained by 1H NMR. On-line near infrared (NIR) measurement was found to be more accurate because it provided many more data points and avoided sampling during the polymerization reaction. It also allowed the determination of kinetic parameters with, for example, the calculation of an apparent first-order rate constant. All the results suggest that FTNIR spectroscopy is a valuable tool to assess kinetic data. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4933,4940, 2004 [source] Solution structure determination of oligoureas using methylene spin state selective NMR at 13C natural abundanceMAGNETIC RESONANCE IN CHEMISTRY, Issue 10 2008Gilles Guichard Abstract Ability of N,N,-linked oligoureas containing proteinogenic side chains to adopt a stable helix conformation in solution has been described recently. NMR as well as circular dichroism (CD) spectroscopies were employed to gain insight into their specific fold. It is herein proposed to extend the structural information available on these peptidomimetics by an advantageous use of a methylene spin state selective NMR experiment. Homodecoupling provided by the pulse scheme made it possible to readily measure conformation-dependent 3JHH constants that are difficult if not impossible to obtain with standard NMR experiments. Adding those couplings to the NMR restraints improved the quality of the structure calculations significantly, as judged by a ca 30% decrease of the root mean square deviation (RMSD) obtained over an ensemble of 20 structures. Moreover, accurate determination of individual 1JCH couplings within each methylene group revealed uniform values throughout the oligourea sequence, with 1JCH systematically slightly larger for the pro-S hydrogen than for the pro-R. As shown in this study, the methylene spin state selective NMR experiment displays a good intrinsic sensitivity and could therefore provide valuable structural information at 13C natural abundance for peptidomimetic molecules and foldamers bearing diastereotopic methylene protons. Copyright © 2008 John Wiley & Sons, Ltd. [source] Cation-, interaction between the aromatic organic counterion and DTAB micelle in mixed solventsCHINESE JOURNAL OF CHEMISTRY, Issue 10 2004Dong-Shun Deng Abstract The cation-, interaction between the aromatic organic counterion potassium hydrogen phthalate (KHP) and DTAB micelle in aqueous mixture of EG was investigated, using the techniques of conductivity measurements, W absorption spectrum and NMR spectrum. The conductivity and UV spectrum studies were with respect to the effect of KHP on DTAB and that of DTAB micelle on KHP, respectively. According to the chemical shift changes of the aromatic ring and the surfactant methylene protons, it can be assumed that KHP penetrated into DTAB micelle with its carboxylic group protruding out of the micellar surface. And the strength of the interaction became weaker with the content of EG in the mixed solvent increasing. [source] | ||||||||||