NMR Spectral Methods (nmr + spectral_methods)

Distribution by Scientific Domains

Selected Abstracts

Novel Sesquiterpenoids from Siegesbeckia orientalis

Ying Xiang
Five new sesquiterpenoids, namely, 8, -(angeloyloxy)-4,,6,,15-trihydroxy-14-oxoguaia-9,11(13)-dien-12-oic acid 12,6-lactone (1), 4,,6,,15-trihydroxy-8, -(isobutyryloxy)-14-oxoguaia-9,11(13)-dien-12-oic acid 12,6-lactone (2), 11,12,13 - trinorguai-6-ene-4,,10, -diol (3), (1(10)E,4E,8Z)-8-(angeloyloxy)-6,,15-dihydroxy-14-oxogermacra-(1(10),4,8,11(13)-tetraen-12-oic acid 12,6-lactone (9), and (1(10)E,4,)-8, -(angeloyloxy)-6,,14,15-trihydroxygermacra-1(10),11(13)-dien-12-oic acid 12,6-lactone (11), and three new artifacts, (1(10)E,4Z)-8, -(angeloyloxy)-9, -ethoxy-6,,15-dihydroxy-14-oxogermacra-1(10),4,11(13)-trien-12-oic acid 12,6-lactone (6), (1(10)E,4Z)-8, -(angeloyloxy)-9,,13-diethoxy-6,,15-dihydroxy-14-oxogermacra-1(10),4-dien-12-oic acid 12,6-lactone (7), and (1(10)E,4Z)-8, -(angeloyloxy)-9, -ethoxy-6,,15-dihydroxy-13-methoxy-14-oxogermacra-1(10),4-dien-12-oic acid 12,6-lactone (8), together with the three known sesquiterpenoids 4, 5, and 10, were isolated from the aerial parts of Sie esbeckia orientalis,L. Their structures were established by spectral methods, especially 1D- and 2D-NMR spectral methods. [source]

Synthesis and characterization of dicyanate monomers containing methylene spacers

G. Anuradha
Abstract The bisphenols containing methylene spacer were prepared by treating eugenol/2-allyl phenol with 2,6-dimethyl phenol/guiacol/o -cresol in the presence of AlCl3. All the bisphenols were converted to their respective cyanate esters by treating with CNBr. The structural confirmation was done by FTIR, 1H NMR, 13C NMR spectral methods, and elemental analysis. Thermal characterization was done by DSC and TGA. DSC transition shows that the Tg is in the range of 208,239C. The Tg is highest for the cyanate ester Cy(b) with symmetric structure. The Tg of the cured network depends on the length and symmetry of the monomer, Tg being higher for shorter and the para-substituted monomers. The T10 values are in the range of 364,381C. The char yield is in the range of 47,53%. From the char yield, the limiting oxygen index (LOI) value was determined, which is used to confirm the flame retardancy of the cyanate ester resins. 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

Synthesis of a cellulose-grafted polymeric support and its application in the reductions of some carbonyl compounds

Poonam K. Dhiman
Abstract The reduction of carbonyl compounds by borohydride supported on a cellulose,anion exchange resin is known. The synthesis of a graft copolymer of cellulose and poly(4-vinyl pyridine) [CellO- g -poly(4-VP)] has been carried out with ceric ions as a redox initiator. A postgrafting treatment of CellO- g -poly(4-VP) with sodium borohydride has produced CellO- g -poly(4-VP) borane, a polymer-supported reducing agent. Optimum conditions pertaining to the maximum percentage of grafting have been evaluated as a function of the concentrations of the initiator, monomer, and nitric acid, amount of water, time, and temperature. The maximum percentage of grafting (585%) has been obtained with 0.927 mol/L of 4-vinyl pyridine and 0.018 mol/L of ceric ammonium nitrate in 120 min at 45C. The polymeric support, CellO- g -poly(4-VP) borane, has been used for reduction reactions of different carbonyl compounds such as benzaldehyde, cyclohexanone, crotonaldehyde, acetone, and furfural. The graft copolymer has been characterized with IR and thermogravimetric analysis. The grafted cellulose has been found to be thermally stable. The reduced products have been characterized with IR and NMR spectral methods. The reagent has been reused for the reduction of a fresh carbonyl compound, and it has been observed that the polymeric reagent reduces the compounds successfully but with a little lower product yield. 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

Complete assignment of the 1H and 13C NMR spectra of garciniaphenone and keto-enol equilibrium statements for prenylated benzophenones

Priscilla B. M. C. Derogis
Abstract This article reports the structural elucidation by IR, UV and MS spectroscopic data along with 1H and 13C NMR chemical shift assignments of two benzophenones isolated from the fruit pericarp of Garcinia brasiliensis Mart. (Clusiaceae): garciniaphenone, (1R,5S,7S)-3-benzoyl-4-hydroxy-6,6-dimethyl-5,7-di(3-methyl-2-butenyl)bicyclo[3.3.1]non-3-ene-2,9-dione, a novel triprenylated benzophenone; and 7- epi -clusianone, a tetraprenylated benzophenone that has already been extracted from another species of the same family. Furthermore, the keto-enol tautomeric equilibrium at solution-state was described for these compounds by 1D and 2D NMR spectral methods and one attempt to rationalize the different ratios between the noted tautomers was based on stereochemical features. Copyright 2008 John Wiley & Sons, Ltd. [source]