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Comparison of the substituent effects on the 13C NMR with the 1H NMR chemical shifts of CHN in substituted benzylideneanilines
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Fifty‐two samples of substituted benzylideneanilines XPhCH?NPhYs (XBAYs) were synthesized, and their NMR spectra were determined in this paper. Together with the NMR data of other 77 samples of XBAYs quoted from literatures, the 1H NMR chemical shifts (δH(CH?N)) and 13C NMR chemical shifts (δC(CH?N)) of the CH?N bridging group were investigated for total of 129 samples of XBAYs. The result shows that the δH(CH?N) and δC(CH?N) have no distinctive linear relationship, which is contrary to the theoretical thought that declared the δH(CH?N) values would increase as the δC(CH?N) values increase. With the in‐depth analysis, we found that the effects of σF and σR of X/Y group on the δH(CH?N) and the δC(CH?N) are opposite; the effects of the substituent specific cross‐interaction effect between X and Y (Δσ2) on the δH(CH?N) and the δC(CH?N) are different; the contributions of parameters in the regression equations of the δH(CH?N) and the δC(CH?N) [Eqns 4 and 7), respectively] also have an obvious difference. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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The 1H chemical shifts of 124 compounds containing a variety of functional groups have been recorded in CDCl3 and DMSO-d6 (henceforth DMSO) solvents. The 1H solvent shift Delta delta = delta(DMSO) - delta(CDCl3) varies from -0.3 to +4.6 ppm. This solvent shift can be accurately predicted (rms error 0.05 ppm) using the charge model of alpha, beta, gamma and long-range contributions. The labile protons of alcohols, acids, amines and amides give both, the largest solvent shifts and the largest errors. The contributions for the various groups are tabulated and it is shown that for H.C.C.X gamma-effects (X = OH, NH, =O, NH.CO) there is a dihedral angle dependence of the gamma-effect. The group contributions are discussed in terms of the possible solvent-solute interactions. For protic hydrogens, hydrogen bonding is the dominant interaction, but for the remaining protons solvent anisotropy and electric field effects appear to be the major factors. 相似文献
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《Magnetic resonance in chemistry : MRC》2003,41(4):269-272
A series of areneboronic acids were studied by NMR spectroscopy. Increments for the 1H and 13C chemical shifts caused by the boronic acid substituent B(OH)2 in areneboronic acids were determined. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
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Mika Tiainen Hannu Maaheimo Pasi Soininen Reino Laatikainen 《Magnetic resonance in chemistry : MRC》2010,48(2):117-122
The one‐ and two‐bond 13C isotope shifts, typically ?1.5 to ?2.5 ppb and ?0.7 ppb respectively, in non‐cyclic aliphatic systems and up to ?4.4 ppb and ?1.0 ppb in glucose cause effects that need to be taken into account in the adaptive NMR spectral library‐based quantification of the isotopomer mixtures. In this work, NMR spectral analyses of some 13C‐labelled amino acids, D ‐glucose and other small compounds were performed in order to obtain rules for prediction of the 13C isotope effects on 1H chemical shifts. It is proposed that using the additivity rules, the isotope effects can be predicted with a sufficient accuracy for amino acid isotopomer applications. For glucose the effects were found strongly non‐additive. The complete spectral analysis of fully 13C‐labelled D ‐glucose made it also possible to assign the exocyclic proton signals of the glucose. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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Abraham RJ Byrne JJ Griffiths L Koniotou R 《Magnetic resonance in chemistry : MRC》2005,43(8):611-624
The (1)H NMR spectra of a number of alcohols, diols and inositols are reported and assigned in CDCl(3), D(2)O and DMSO-d(6) (henceforth DMSO) solutions. These data were used to investigate the effects of the OH group on the (1)H chemical shifts in these molecules and also the effect of changing the solvent. Inspection of the (1)H chemical shifts of those alcohols which were soluble in both CDCl(3) and D(2)O shows that there is no difference in the chemical shifts in the two solvents, provided that the molecules exist in the same conformation in the two solvents. In contrast, DMSO gives rise to significant and specific solvation shifts. The (1)H chemical shifts of these compounds in the three solvents were analysed using the CHARGE model. This model incorporates the electric field, magnetic anisotropy and steric effects of the functional group for long-range protons together with functions for the calculation of the two- and three-bond effects. The long-range effect of the OH group was quantitatively explained without the inclusion of either the C--O bond anisotropy or the C--OH electric field. Differential beta and gamma effects for the 1,2-diol group needed to be included to obtain accurate chemical shift predictions. For DMSO solution the differential solvent shifts were calculated in CHARGE on the basis of a similar model, incorporating two-bond, three-bond and long-range effects. The analyses of the (1)H spectra of the inositols and their derivatives in D(2)O and DMSO solution also gave the ring (1)H,(1)H coupling constants and for DMSO solution the CH--OH couplings and OH chemical shifts. The (1)H,(1)H coupling constants were calculated in the CHARGE program by an extension of the cos(2)phi equation to include the orientation effects of electronegative atoms and the CH--OH couplings by a simple cos(2)phi equation. Comparison of the observed and calculated couplings confirmed the proposed conformations of myo-inositol, chiro-inositol, quebrachitol and allo-inositol. The OH chemical shifts were also calculated in the CHARGE program. Comparison of the observed and calculated OH chemical shifts and CH.OH couplings suggested the existence of intramolecular hydrogen bonding in a myo-inositol derivative. 相似文献
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《Magnetic resonance in chemistry : MRC》2002,40(7):480-482
1H, 13C and 15N NMR chemical shifts of 10 substituted pyrazolo[1,5‐a]pyrimidines were assigned based on DQF 1H, 1H COSY, PFG 1H, 13C HMQC and PFG 1H,X (X = 13C and 15N) HMBC experiments and on literature data. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
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This work presents the substituent effects on the 1H and 13C NMR chemical shifts in the cis-isomer of 3-Y-cyclohexanols (Y = Cl, Br, I, CH3, N(CH3)2 and OCH3) and 3-Y-1-methoxycyclohexanes (Y = F, Cl, Br, I, CH3, N(CH3)2 and OCH3). It was observed that the H-3 chemical shift, due to the substituent alpha-effect, increases with the increase of substituent electronegativity when Y is from the second row of the periodic table of elements, (CH3 *sigma(C3--H3a) interaction energy. This interaction energy, for the halogenated compounds, decreases with an increase in size of the halogen, and this is a possible reason for the largest measured chemical shift for H-3 of the iodo-derivatives. The beta-effect of the analyzed compounds showed that the chemical shift of hydrogens at C-2 and C-4 increases with the decrease of n(Y) --> *sigma(C2-C3) and n(Y) --> *sigma(C3-C4) interaction energies, respectively, showing a behavior similar to H-3. The alpha-effect on 13C chemical shifts correlates well with substituent electronegativity, while the beta-effect is inversely related to electronegativity in halogenated compounds. NBO analysis indicated that the substituent inductive effect is the predominant effect on 13C NMR chemical shift changes for the alpha-carbon. It was also observed that C-2 and C-4 chemical shifts for compounds with N(CH3)2, OCH3 and F are more shielded in comparison to the compounds having a halogen, most probably because of the larger interaction of the lone pair of more electronegative atoms (n(N) > n(O) > n(F)) with *sigma(C2-C3), *sigma(C3-C4) and *sigma(C3-H3a) in comparison with the same type of interaction with the lone pair of the other halogens. 相似文献
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Honeyman B Spalding C Jensen D Haddon RC 《Magnetic resonance in chemistry : MRC》2005,43(12):1053-1056
9-Hydroxyphenalenone is a planar multicyclic beta-keto-enol that demonstrates C2V symmetry on the NMR timescale. Off-axis substitution breaks the molecular symmetry and results in tautomers. 1H and 13C NMR assignments were made for 9-hydroxyphenalenone and three methyl derivatives, and the solution-phase tautomers were determined. 相似文献
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《Magnetic resonance in chemistry : MRC》2002,40(8):554-556
The 1H and 13C NMR resonances for four bisquinolinium and four bisisoquinolinium dibromides were completely and unequivocally assigned, using the concerted application of one‐ and two‐dimensional NMR techniques including nuclear Overhauser effect difference, DEPT, COSY, HETCOR and long‐range 13C–1H correlation spectroscopy. Atomic charges of the heterocyclic moieties of model cations such as 1‐methylquinolinium and 2‐methylisoquinolinium are shown to be linearly related to the 13C chemical shifts of the cationic heads of the title compounds. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
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The quantitative structure–activity relationship models of 40 phenylhydrazine-substituted tetronic acid derivatives were established between the 1H nuclear magnetic resonance (NMR) and 13C NMR chemical shifts and the antifungal activity against Fusarium graminearum, Botrytis cinerea, Rhizoctonia cerealis, and Colletotrichum capsici. The models were validated by R, R2, RA2, variance inflation factor, F, and P values testing and residual analysis. It was concluded from the models that the 13C NMR chemical shifts of C8, C10, C7, and the 1H NMR chemical shifts of Ha contributed positively to the activity against Fusarium graminearum, Botrytis cinerea, Colletotrichum capsici, and Rhizoctonia cerealis, respectively. The models indicated that decreasing the election cloud density of specific nucleuses in compounds, for example, by the substituting of electron withdrawing groups, would improve the antifungal activity. These models demonstrated the practical application meaning of chemical shifts in the quantitative structure–activity relationship study. Furthermore, a practical guide was provided for further structural optimization of the antifungal phenylhydrazine-substituted tetronic acid derivatives based on the 1H NMR and 13C NMR chemical shifts. 相似文献
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《Magnetic resonance in chemistry : MRC》2003,41(9):731-734
An NMR study of one new and several known abietane diterpenes isolated from the roots of Aegiphila lhotzkyana is described. In addition to 1D NMR, several 2D shift‐correlated NMR pulse sequences (1H–1H‐COSY, NOESY, HMQC and HMBC) were used to establish all the structures, and unambiguously perform the 1H and 13C chemical shift assignments of the new natural diterpene and three derivatives, the NMR data for which have not been reported previously. Revision of current data assignment for teuvincenone H is also suggested. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
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《Magnetic resonance in chemistry : MRC》2003,41(9):729-730
The characterization of four aryl diisoprenes was carried out by 1D‐ and 2D‐NMR methods, which permitted the assignment of the signals of all protons and all carbon atoms. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
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Valentin A. Semenov Dmitry O. Samultsev Leonid B. Krivdin 《Magnetic resonance in chemistry : MRC》2020,58(6):532-539
The density functional theory calculation of 1H and 13C NMR chemical shifts in a series of ten 10 classically known Strychnos alkaloids with a strychnine skeleton was performed at the PBE0/pcSseg-2//pcseg-2 level. It was found that calculated 1H and 13C NMR chemical shifts provided a markedly good correlation with experiment characterized by a mean absolute error of 0.08 ppm in the range of 7 ppm for protons and 1.67 ppm in the range of 150 ppm for carbons, so that a mean absolute percentage error was as small as ~1% in both cases. 相似文献
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The complete 1H and 13C NMR assignment of four 6,7-benzo-fused furocoumarins (1-4) and three 3,4-benzo-fused furocoumarins (5-7) has been performed using 1D and 2D NMR techniques, including COSY, HMQC and HMBC experiments. 相似文献
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Raymond J. Abraham Lee Griffiths Manuel Perez 《Magnetic resonance in chemistry : MRC》2014,52(7):395-408
The 1H chemical shifts of 48 amides in DMSO solvent are assigned and presented. The solvent shifts Δδ (DMSO‐CDCl3) are large (1–2 ppm) for the NH protons but smaller and negative (?0.1 to ?0.2 ppm) for close range protons. A selection of the observed solvent shifts is compared with calculated shifts from the present model and from GIAO calculations. Those for the NH protons agree with both calculations, but other solvent shifts such as Δδ(CHO) are not well reproduced by the GIAO calculations. The 1H chemical shifts of the amides in DMSO were analysed using a functional approach for near ( ≤ 3 bonds removed) protons and the electric field, magnetic anisotropy and steric effect of the amide group for more distant protons. The chemical shifts of the NH protons of acetanilide and benzamide vary linearly with the π density on the αN and βC atoms, respectively. The C=O anisotropy and steric effect are in general little changed from the values in CDCl3. The effects of substituents F, Cl, Me on the NH proton shifts are reproduced. The electric field coefficient for the protons in DMSO is 90% of that in CDCl3. There is no steric effect of the C=O oxygen on the NH proton in an NH…O=C hydrogen bond. The observed deshielding is due to the electric field effect. The calculated chemical shifts agree well with the observed shifts (RMS error of 0.106 ppm for the data set of 257 entries). Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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Valentin A. Semenov Dmitry O. Samultsev Leonid B. Krivdin 《International journal of quantum chemistry》2020,120(19):e26348
The PBE0/pcSseg-2//pcseg-2 calculations of 1H and 13C NMR chemical shifts were performed for a classical series of 12 Strychnos alkaloids (except for the earlier studied parent strychnine), namely akuammicine, isostrychnine, rosibiline, tsilanine, spermostrychnine, diaboline, cyclostrychnine, henningsamide, strychnosilidine, strychnobrasiline, holstiine, and icajine. It was found that the calculated 1H and 13C NMR chemical shifts show markedly good correlations with available experimental data, as characterized by a mean absolute error of 0.22 ppm for the range of 8 ppm for protons and 1.97 ppm for the range of 180 ppm for carbons. Complementarily, the present results provide essential NMR update and fill a gap in the NMR data of this distinguished group of vitally important natural products. 相似文献
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《Magnetic resonance in chemistry : MRC》2002,40(10):659-665
The phenylselenenylmenthane and ‐menthene derivatives 1–4 were studied in terms of 1H and 13C signal assignments, conformational analysis and also complexation shifts (Δδ) and dispersion effects (Δν) observed when non‐racemic (ca 2 : 1) mixtures of the chiral selenides were exposed to an equimolar amount of the chiral dirhodium complex Rh*. The complexation site is the selenium atom exclusively. Whereas Δδ values are moderate or small, dispersed signals (split into two owing to the existence of diastereomeric adducts) can be observed, many of which are large enough for a facile determination of enantiomeric ratios of the selenides irregardless of the conformational behaviour of the selenides and the adduct composition. Thus, the ‘dirhodium method’ is simple and reliable for chiral recognition in the class of organoselenium compounds which is gaining increasing importance in developing new techniques of asymmetric synthesis. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
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Lima AF Mileo PG Andrade-Neto M Braz-Filho R Silveira ER Pessoa OD 《Magnetic resonance in chemistry : MRC》2009,47(2):165-168
Two new polymethoxylated flavonoids, 2',5',6'-trimethoxy-[2',3' : 3',4']furano dihydrochalcone and 2,4',4,5-tetramethoxy-[2',3' : 6,7]-furanodihydroaurone, were isolated from the root barks of Lonchocarpus araripensis, along with the known compounds 3,4,5,6-tetramethoxy-[2',3' : 7,8]-furanoflavan, 3,6-dimethoxy-1',1'-dimethylcromene-[2',3' : 7,8]-flavone, 3',4'-methylenodioxy-5,6-dimethoxy-[2',3' : 7,8]-furanoflavone, 3,5,6-trimethoxy-[2',3' : 7,8]-furanoflavanone, 3,5,6-trimethoxy-[2',3' : 7,8]-furanoflavone, and 6alpha-hydroxy-medicarpin. The complete (1)H and (13)C NMR assignments of the new furan flavonoids were performed using 1D and 2D pulse sequences, including COSY, HSQC, and HMBC experiments, and comparison with spectral data for analog compounds from the literature, particularly for the new furanodihydroaurone because of several inconsistencies on the carbonyl chemical shifts from the literature. 相似文献