NMR Spectral Analysis (nmr + spectral_analysis)

Distribution by Scientific Domains

Selected Abstracts

Alkaloids from Fritillaria Hupehensis

Yong-Hui ZHANG
Abstract Phytochemical investigation of the bulbs of Fritillaria hupehensis resulted in the isolation and structural elucidation of a new highly conjugated alkaloid of veratramine type identified as 3,,23, -dihydroxy-7,12(14)-dien-5, -veratramin-6-one (1), together with two known alkaloids, ebeinine (2) and zhebeinine (3), which were isolated for the first time from F. hupehensis. The structures of alkaloids 1,3 were established by extensive 1D and 2D NMR spectral analyses. [source]

NMR and DFT investigations of the substituent and solvent effect on amino,imino tautomerism in acridin-9-amines substituted at the exocyclic nitrogen atom,

Youssif Ebead
Abstract The 1H and 13C NMR spectra of 9-(methoxyamino)acridine (1) and 9-hydrazinoacridine (2) show that these compounds exist principally in the imino tautomeric form in CDCl3, acetone- d6, CD3CN, DMSO- d6 and Py- d5, all solvents with different polarities and abilities to participate in specific interactions. The spectra of the other two compounds investigated,N -(2-chloroethyl)acridin-9-amine (3) and N -(5-methylpyridin-2-yl)acridin-9-amine (4),indicate that they coexist in the amino and imino forms. The amino tautomer of compound 3 predominates in CDCl3, CD3CN and Py- d5 and that of compound 4 in CDCl3 and Py- d5. On the other hand, the amino and imino forms of compound 3 coexist in acetone- d6 and probably DMSO- d6, whereas those of compound 4 coexist in acetone- d6 and DMSO- d6. The positions of the signals in the NMR spectra compare qualitatively with those predicted computationally at the GIAO/DFT level of theory. The equilibrium constants predicted by the DFT(PCM) method are in agreement with the results of NMR spectral analysis. In general, both the data predicted at the DFT level of theory and x-ray structural data show that the imino tautomers display a ,butterfly'-type geometry, whereas the amino forms are characterized by an almost flat acridine moiety. Electron-attracting substituents at the exocyclic N atom improve the stability of the imino form, and electron-withdrawing substituents do likewise for the amino form. The importance of tautomeric phenomena in the context of the ability of acridin-9-amines to participate in specific interactions is outlined in brief, as are the possible applications of these compounds as probes of environmental properties. Copyright 2005 John Wiley & Sons, Ltd. [source]

Silica Reinforced Organic,Inorganic Hybrid Polyurethane Nanocomposites From Sustainable Resource

Deewan Akram
Abstract Polyol/nanosilica organic,inorganic hybrids (Si/Lpol) were prepared through facile sol,gel chemistry. Tetraethoxyorthosilane (TEOS) and linseed polyol (Lpol) obtained by hydroxylation of linseed oil were used as inorganic and organic precursors, respectively. Si/Lpol was further treated with toluene-2,4-diisocyanate (TDI) to obtain silica embedded polyurethane (Si/LPU). The structure of the organic,inorganic hybrid was confirmed by FTIR, 1H NMR, and 13C NMR spectral analysis. The polyol/nanosilica network shows strong interaction with the remnant polyol backbone through hydrogen bonding, which also has bearing on Tg of polymers. Morphological studies of Si/LPU show the formation of uniform, spherical silica nanoparticles of 2,30,nm size embedded in the polymer matrix. Si/LPU was further reinforced with 2 and 5,wt.-% fumed silica (FS-Si/LPUs); their morphology revealed a carpet layer formation on top of Si/LPU. Thermogravimetric analysis showed improved thermal stability of Si/LPU and FS-Si/LPUs. The polymers exhibit mild to moderate antibacterial behavior against E. coli and S. aureus, respectively, and will pave way in plethora of biological and chemical applications as coating materials. [source]

Influence of feeding strategies of mixed microbial cultures on the chemical composition and microstructure of copolyesters P(3HB-co-3HV) analyzed by NMR and statistical analysis

G. Ivanova
Abstract NMR spectroscopy was applied for quantitative and qualitative characterization of the chemical composition and microstructure of a series of poly(3-hydroxybutyrate- co -3-hydoxyvalerate) copolymers, P(3HB- co -3HV), synthesized by mixed microbial cultures at several different feeding strategies. The monomer sequence distribution of the bacterially synthesized P(3HB- co -3HV) was defined by analysis of their high-resolution 1D 13C NMR and 2D 1H/13C HSQC and 1H/13C HMBC NMR spectra. The results were verified by employment of statistical methods and suggest a block copolymer microstructure of the P(3HB- co -3HV) copolymers studied. Definitive distinction between block copolymers or a mixture of random copolymers could not be achieved. NMR spectral analysis indicates that the chemical composition and microstructure of the copolymers can be tuned by choosing a correct feeding strategy. Copyright 2009 John Wiley & Sons, Ltd. [source]

Complete assignments of 1H and 13C NMR spectral data for 7,7,-dihydroarylnaphthalene lignan lactones

Rosangela da Silva
Abstract In this article we present a complete 1H and 13C NMR spectral analysis of three 7,7,-dihydroarylnaphthalene lignan lactones using modern NMR techniques such as COSY, HSQC, HMBC and NOE experiments. Complete assignment and homonuclear hydrogen coupling constant measurements were performed. Copyright 2009 John Wiley & Sons, Ltd. [source]

1H, 13C and 31P NMR spectral analysis of monoalkyl (,-anilinobenzyl)phosphonates and their dipalladium(II) metallocyclic complexes

Ljerka Tu, ek-Bo
Abstract A 1H, 13C and 31P NMR study of monoethyl (HL1) and monobutyl (HL2) esters of (,-anilinobenzyl)phosphonic acid and their metallocyclic dipalladium complexes (Pd2L4,L = L1, L2) in DMSO- d6 was performed, based on 1D and 2D homo- and heteronuclear experiments including 1H,13C,31P,APT,1H,1H COSY, 1H,13C COSY, gs-HMQC and gs-HMBC NMR techniques. The results obtained are discussed with respect to those for some palladium(II) complexes reported for various anilinobenzylphosphonate derivatives. Copyright 2002 John Wiley & Sons, Ltd. [source]

NMR and UPLC-qTOF-MS/MS characterisation of novel phenylethanol derivatives of phenylpropanoid glucosides from the leaves of strawberry (Fragaria ananassa cv. Jonsok)

Kati Hanhineva
Abstract Introduction Strawberry (Fragaria ananassa) is rich in polyphenols, particularly anthocyanins, flavonols, condensed tannins and ellagic tannins. In addition to the fruits, the leaves of strawberry also contain a wide range of phenolic compound classes, but have not been investigated to the same extent as the fruit. Objective To characterise a metabolite group present in the leaves of strawberry, that was not amenable for identification based on earlier information available in the literature. Methodology Methanolic extracts of strawberry leaves were analysed by UPLC-qTOF-MS/MS and iterative quantum mechanical NMR spectral analysis. Results The structures of phenylethanol derivatives of phenylpropanoid glucosides Eutigoside A ( F4) and its two isomeric forms 2-(4-hydroxyphenyl)ethyl-[6- O -(Z)-coumaroyl]- ,- d -glucopyranoside ( F6) and 4-(2-hydroxyethyl)phenyl-[6- O -(e)-coumaroyl]- ,- d -glucopyranoside ( F1) were resolved by NMR and UPLC-qTOF-MS/MS. In addition, two other derivatives of phenylpropanoid glucosides similar to Eutigoside A but possessing different phenolic acid moieties, namely Grayanoside A ( F5) and 2-(4-hydroxyphenyl)ethyl-[6- O -(e)-caffeoyl]- ,- d -glucopyranoside ( F14), were similarly identified. Also, accurate characteristic coupling constants for the subunits are reported and their usefulness in structural analysis is highlighted. Conclusion Chemical analysis of the leaves of strawberry (Fragaria ananassa cv. Jonsok) resulted in the identification of a compound class, phenylethanol derivatives of phenylpropanoid glycosides, not previously found in strawberry. Copyright 2009 John Wiley & Sons, Ltd. [source]

Polymerization and characterization of various di(pyridine)bis(trihalophenolato)cobalt(II) complexes in solid and melt states

Neslin Kesici
Abstract The syntheses of distorted tetrahedral bis(pyridine)bis(trihalophenolato)cobalt(II) complexes from an aqueus solution were achieved and their characterization by FT-IR, X-ray, DSC, UV-visible and elemental analysis in solid state or in melt form is reported. Polymerizations of these complexes were accomplished either at constant temperature, employing different time intervals or constant decomposition times while varying the temperature range. The slow decomposition at constant temperature leads to long chain products, whereas long chains formed at higher temperatures were during a constant time. The resulting poly(dihalophenylene oxide)s were characterized by FT-IR, 1H NMR, 13C NMR spectral analysis, differential scanning calorimetry and molecular weight determinations by viscometric method. 2001 Society of Chemical Industry [source]

Palladium,Schiff base,triphenylphosphine catalyzed oxidation of alcohols

Dileep R.
Abstract Novel palladium(II)- N -(2-pyridyl)- N,-(5- R -salicylidene) hydrazine triphenylphosphine complexes were synthesized and characterized by UV, IR, 1H NMR and 31P NMR spectral analysis, C, H, N analysis and magnetic susceptibility measurements. The complexes were effective in the catalytic oxidation of primary and secondary alcohols in presence of N -methyl-morpholine- N -oxide as oxidant. The oxidation reactions were carried out in dichloromethane. A mechanistic study of the above reactions has been proposed. Copyright 2010 John Wiley & Sons, Ltd. [source]

The effect of biothiol on UV irradiated ,-lipoic acid

BIOFACTORS, Issue 4 2008
Naoki Wada
Abstract ,-Lipoic acid (LA) and its reduced form dihydrolipoic acid (DHLA) are well known as strong antioxidants. LA has the characteristic distorted five membered 1,2-dithiolane ring, which is quite vulnerable to UV irradiation. The UV induced decomposition of LA and the effect of the following addition of biothiols to the photoirradiated solution of LA were investigated by UV-vis spectrometry and 1H NMR spectral analysis. The mechanism of UV irradiated LA decomposition was proposed based on the results obtained from NMR and GPC measurements. [source]

Synthesis and Characterization of the D5h Isomer of the Endohedral Dimetallofullerene Ce2@C80: Two-Dimensional Circulation of Encapsulated Metal Atoms Inside a Fullerene Cage

Michio Yamada Dr.
Abstract Herein we show the synthesis and characterization of the second known Ce2@C80 isomer. A 13C,NMR spectroscopic study revealed that the structure of the second isomer has D5h symmetry. Paramagnetic NMR spectral analysis and theoretical calculation display that the encapsulated Ce atoms circulate two-dimensionally along a band of ten contiguous hexagons inside a D5h -C80 cage, which is in sharp contrast to the three-dimensional circulation of two Ce atoms in an Ih -C80 cage. The electronic properties were revealed by means of electrochemical measurements. The D5h isomer of Ce2@C80 has a much smaller HOMO,LUMO gap than cluster fullerenes (M3N@C80, M=Sc, Tm, and Lu) with the same D5h -C80 cages. The chemical reactivity was investigated by using disilirane as a chemical probe. The high thermal reactivity toward 1,1,2,2-tetramesityl-1,2-disilirane is consistent with the trends of the redox potentials and the lower LUMO level of the D5h isomer of Ce2@C80 compared with that of C60. [source]