Effets de substituants en résonance magnétique nucléaire du 13C. Etude des dérivés du phényl-2 furanne et du phényl-2 pyrrole

1976 ◽  
Vol 54 (11) ◽  
pp. 1827-1836 ◽  
Author(s):  
Gilbert Dana ◽  
Odile Convert ◽  
Jean-Pierre Girault ◽  
Etienne Mulliez
Keyword(s):  
Electron Density ◽  
Benzene Ring ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Para Position ◽  
Simple Relationship ◽  
Résonance Magnétique ◽  
Derivatives Of ◽  
C Nmr

The 13C nmr spectra of derivatives of phenylfuran and phenylpyrrole were studied. The α and β carbons of the heterocycle, conjugated to the substituent X in the para position of the benzene ring, show variations in chemical shifts which bear a simple relationship to the donor properties of X. This is interpreted by the change in electron density caused by this conjugation. This conjugation seems more important in the series of 2-phenylpyrroles than in the series of 2-phenyl-furans especially if the behaviour of then α position is considered.[Journal translation]

Proximity and conformation effects in 29Si and 13C NMR spectra of di-ortho substituted trimethylsiloxybenzenes

1990 ◽  
Vol 55 (8) ◽  
pp. 2027-2032 ◽  
Author(s):  
Jan Schraml ◽  
Robert Brežný ◽  
Jan Čermák
Keyword(s):  
Benzene Ring ◽  
13C Nmr ◽  
Proximity Effect ◽  
Nmr Spectra ◽  
Methoxy Group ◽  
Chemical Shifts ◽  
Proximity Effects ◽  
13C Nmr Spectra ◽  
Methoxy Groups ◽  
C Nmr

29Si and 13C NMR spectra of five 4-substituted 2,6-dimethoxytrimethylsiloxybenzenes were studied with the aim to elucidate the nature of the deshielding proximity effects observed in the spectra of ortho substituted trimethylsiloxybenzenes. The sensitivity of 29Si chemical shifts to para substitution is in the studied compounds essentially the same as in mono ortho methoxytrimethylsiloxybenzenes. The deshielding proximity effect of the ìsecondî methoxy group is somewhat smaller than that of the ìfirstî group. The present results indicate that the two methoxy groups assume coplanar conformations with the benzene ring and are turned away from the trimethylsiloxy group which is not in the benzene plane. It is argued that in mono ortho methoxytrimethylsiloxybenzenes the two substituent groups adopt the same conformations as in the compounds studied here.

Increments for 1H and 13C NMR chemical shifts in pinacol arylboronates

2012 ◽  
Vol 90 (1) ◽  
pp. 71-74
Author(s):  
Di Qiu ◽  
Zhitong Zheng ◽  
Fanyang Mo ◽  
Yan Zhang ◽  
Jianbo Wang
Keyword(s):  
Benzene Ring ◽  
13C Nmr ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Cross Coupling ◽  
Coupling Reactions ◽  
1H And 13C Nmr ◽  
Nmr Chemical Shifts ◽  
Cross Coupling Reactions ◽  
C Nmr

Arylboronates are important compounds widely used in cross-coupling reactions. By analyzing the NMR spectra data of a variety of pinacol arylboronates, we have determined the increments for 1H and 13C NMR chemical shifts caused by a pinacol boronate substituent in the benzene ring. These data can be used in the estimation of chemical shifts of aromatic pinacol boronates.

Synthetic and 1H and 13C NMRSpectral Studies on N-(Mono-substitutedphenyl)- acetamides and Substituted Acetamides, 2/3/4-YC6H4NH-COCH3–iXi (Y = CH3, F, Cl, Br, NO2; X = Cl, CH3; i = 0, 1, 2, 3)

2006 ◽  
Vol 61 (10-11) ◽  
pp. 595-599
Author(s):  
Basavalinganadoddy Thimme Gowda ◽  
Shilpa Lakshmipathy ◽  
Jayalakshmi K. Lakshmipathy
Keyword(s):  
Electron Density ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Nmr Chemical Shifts ◽  
H Nmr ◽  
C Nmr

Nineteen N-(2/3/4-methyl/halo/nitro-phenyl)-acetamides and substituted acetamides, 2/3/4- YC6H4NH-CO-CH3−iXi (Y = CH3, F, Cl, Br or NO2; X = Cl or CH3 and i = 0, 1, 2 or 3), have been prepared, characterized, and their 1H and 13C NMR spectra in solution measured and correlated. 1H and 13C NMR chemical shifts were assigned to the protons and carbon atoms, respectively, in line with those for similar compounds. Since the chemical shifts are dependent on the electron density around the nucleus or associated with the atom to which it is bound, the incremental shifts of the aromatic protons or carbon atoms due to -NH-CO-CH3−iXi and -CO-CH3−iXi (X = Cl or CH3 and i = 0, 1, 2, 3) in all the N-phenyl-substituted acetamides, C6H5NH-CO-CH3−iXi, are calculated by comparing the proton or carbon chemical shifts of these compounds with those of benzene or aniline. The incremental shifts due to the groups in the parent compounds have also been computed by comparing the chemical shifts of the protons or carbon atoms in these compounds with those of benzene or aniline, respectively. The computed incremental shifts and other data were used to calculate the 1H and 13C NMR chemical shifts of the substituted compounds in three different ways. The calculated chemical shifts by the three methods compared well with each other and with the observed chemical shifts, testing the validity of the principle of additivity of the substituent effects in these compounds. The variation of 1H NMR chemical shifts of either the aromatic or N-H protons, with the substituents in N-(phenyl)- and N-(2/3/4-chloro/methylphenyl)-acetamides and substituted acetamides did not follow the same trend, while the variation of the 13C NMR chemical shifts of C-1 and C=O carbon atoms and those of alkyl carbon atoms of these compounds followed more or less the same trend.

29Si (and 13C) NMR spectra of modified silatranyl derivatives of some monosaccharides

1984 ◽  
Vol 49 (12) ◽  
pp. 2897-2902 ◽  
Author(s):  
Jan Schraml ◽  
Aleksandr Mikhailovich Krapivin ◽  
Aleksandr Petrovich Luzin ◽  
Vladimir Mikhailovich Kilesso ◽  
Vadim Aleksandrovich Pestunovich
Keyword(s):  
Molecular Structure ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Distinct Advantage ◽  
13C Nmr Spectra ◽  
Limited Data ◽  
Structural Sensitivity ◽  
Trimethylsilyl Derivatives ◽  
Derivatives Of ◽  
C Nmr

29Si (and 13C) NMR chemical shifts are reported for several 2-carba-3-oxahomosilatranyl (3,9,10-trioxa-6-aza-1-silabicyclo[3.3.4]dodecane-1-yl) and silatranyl (2,8,9-trioxa-5-aza-1-silabicyclo[3.3.3]undecane-1-yl) derivatives of some monosaccharides and other alcohols. The limited data suggest somewhat larger sensitivity of the silicon chemical shifts to molecular structure in 2-carba-3-oxahomosilatranyl derivatives than in silatranyl derivatives. In comparison with trimethylsilyl derivatives homosilatranyl derivatives show lower structural sensitivity of the silicon chemical shift. In some cases, however, larger stability of the silatranyl or 2-carba-3-oxahomosilatranyl derivatives than that of trimethylsilyl derivatives might be a distinct advantage.

Preparation of β-D-Glucopyranosyl Derivatives of 1,6:2,3- and 1,6:3,4-Dianhydro-β-D-hexopyranoses and Their 1H and 13C NMR Spectra

1995 ◽  
Vol 60 (2) ◽  
pp. 311-323 ◽  
Author(s):  
Miloš Buděšínský ◽  
Miloslav Černý ◽  
Ivan Černý ◽  
Stanislav Sámek ◽  
Tomáš Trnka
Keyword(s):  
13C Nmr ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
13C Nmr Spectra ◽  
1H And 13C Nmr ◽  
Derivatives Of ◽  
C Nmr

The corresponding acetylated and free 2-O- and 4-O-glucosyl derivatives of dianhydrohexoses Ib - VIIb and Ic - VIIc have been obtained by the reactions of 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl bromide (IX) with 1,6:3,4- and 1,6:2,3-dianhydro-β-D-hexopyranoses (Ia - VIIa). Structure of the products and the effects of glycosylation upon chemical shifts and conformations of the disaccharides prepared have been studied using 1H and 13C NMR spectra.

13C NMR study of 3-(X-benzal)phthalides and 2-(X-benzal)-1,3-indanediones

1980 ◽  
Vol 45 (10) ◽  
pp. 2772-2778 ◽  
Author(s):  
Eva Solčániová ◽  
Pavol Hrnčiar ◽  
Tibor Liptaj
Keyword(s):  
Chemical Shift ◽  
Nmr Spectra ◽  
Electronic Effect ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Carbonyl Groups ◽  
Aryl Group ◽  
Nmr Study ◽  
Derivatives Of ◽  
C Nmr

13C NMR spectra of 14 derivatives of 3-(X-benzal)phthalides (I) and 10 derivatives of 2-(X-benzal)-1,3-indanediones (II) were investigated. The correlation of 13C chemical shifts of carbon atoms of the phthalide ring with σ-constants showed that the electronic effect of substituents was transmitted from the benzylidene group of 3-(X-benzal)phthalides on the chemical shift of the carbonyl group not only through oxygen, but also through the aromatic ring of the phthalide moiety. The transmission of substituent effects in 2-(X-benzal)-1,3-indanediones on the chemical shift of the carbonyl groups was more pronounced on the carbonyl, which is in the trans-arrangement with respect to the aryl group. This phenomenon was also observed at carbon atoms of the benzene ring of the indanedione moiety closer to the trans-CO group.

Dérivés allyliques de la colonne IV-A, de type R3ECH2CH=CH—CH3 et R3ECH(CH3)CH=CH2. Approche des effets électroniques par résonance magnétique nucléaire 13C et 1H

1983 ◽  
Vol 61 (11) ◽  
pp. 2476-2485 ◽  
Author(s):  
E. Matarasso-Tchiroukhine ◽  
P. Cadiot
Keyword(s):  
Chemical Shifts ◽  
Main Group ◽  
Group Element ◽  
Appreciable Change ◽  
Spectroscopic Parameters ◽  
Group Electronegativity ◽  
Nmr Study ◽  
Résonance Magnétique ◽  
Derivatives Of ◽  
C Nmr

A comparative 1H and 13C nmr study of allylic derivatives of the IV-A group elements, of the type R3ECH2CH=CH—CH31E, Z and R3ECH(CH3)CH=CH2, 2, was performed (R = —C6H5, —CH3, E = C, Si, Ge, Sn, Pb). The present paper dealing with the allylic moiety concerns both the chemical shifts, δ1H and δ13C, and the homonuclear J(H—H) and heteronuclear couplings 1J(13C—H), nJ(13C—E), n = 1 to 4, nJ(E—C—H), n = 2 and 5. The spectra are consistent with a σ-allylic structure. In order to obtain an inductive order for the groups G(E) = —E(C6H5)3 a coherent group electronegativity scale was established. The intrinsic group electronegativities, without appreciable change, obey the following sequence:[Formula: see text]Both the changes along the series, in spectroscopic parameters, δ1H, δ13C, and the unusually large heteronuclear couplings, 2J(E—C—H), 5J(E—C—H), 4J(E—13C) (E = Sn, Pb), are interpreted in terms of an electronic mesomeric donating effect for the substituent σ, R3ECH2— and R3ECH(CH3)—, by σ–π hyperconjugation. Factors intrinsic to the main-group element control the chemical shifts δ1Hα and δ13Cα. The s-character of the bond Cα—Hα appears to control the 1J(13Cα—Hα) couplings; no correlation with a σ → π hyperconjugation could be established.

Pertrimethylsilylation as a method for improvement of chemical shift additivity through conformational homogenization. 1H and 13C NMR spectra of pertrimethylsilylated derivatives of methyl β-D-xylopyranosides

1983 ◽  
Vol 48 (7) ◽  
pp. 1829-1841 ◽  
Author(s):  
Jan Schraml ◽  
Eva Petráková ◽  
Otomar Pihar ◽  
Ján Hirsch ◽  
Václav Chvalovský
Keyword(s):  
Chemical Shift ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Population Analysis ◽  
Coupling Constants ◽  
Proton Proton ◽  
1H And 13C Nmr ◽  
Proton Coupling ◽  
Derivatives Of ◽  
C Nmr

All possible mono-, di-, and tri- O-methyl, O-benzyl, O-benzoyl, and O-acetyl derivatives of methyl β-D-xylopyranoside were fully trimethylsilylated and their 1H and 13C NMR spectra measured in deuteriochloroform solutions. The spectra were analysed and the chemical shifts completely assigned on the basis of decoupling experiments. The proton-proton coupling constants vary only very little throughout the series. Conformer population analysis by the method of average coupling constants shows that trimethylsilylation increases the C1 conformer population and makes the series conformationally homogenous. Owing to this conformational homogeneity chemical shifts (both 1H and 13C) satisfy very well direct additivity rule. It is suggested that pertrimethylsilylation should be employed whenever deviations from chemical shift additivity are caused by conformational mobility of the investigated series of compounds and when bulky groups can stabilize one of the conformers.

Study of Amino-Imino Tautomerism in Derivatives of 2-, 4- and 6-Aminonicotinic Acid

1994 ◽  
Vol 59 (9) ◽  
pp. 2057-2068 ◽  
Author(s):  
Svatava Smrčková ◽  
Kristina Juricová ◽  
Viktor Prutianov
Keyword(s):  
Ir Spectroscopy ◽  
Hydrogen Bonds ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Amino Derivative ◽  
Ionic Character ◽  
H Nmr ◽  
Amino Derivatives ◽  
Derivatives Of ◽  
C Nmr

13C NMR spectra of p-nitrobenzoyl 2-, 4-, and 6-aminopyridine-3-carboxylates, their hydrochlorides, trifluoroacetates and 1-benzyl derivatives were studied. As found from the chemical shifts of pyridine carbon atoms C-2, C-4 and C-6, the free bases exist in the amino form whereas hydrochlorides and 1-substituted pyridinium derivatives in the imino form. Trifluoroacetates of the 2- and 6-amino derivatives have structure similar to that of amidiniumcarboxylates (parallel hydrogen bonds and partially ionic character) whereas trifluoroacetate of the 4-amino derivative is structurally close to the corresponding hydrochloride. The found structures were confirmed by 1H NMR and IR spectroscopy.

17O and 13C NMR spectra of some geminal diacetates

1988 ◽  
Vol 53 (3) ◽  
pp. 588-592 ◽  
Author(s):  
Antonín Lyčka ◽  
Josef Jirman ◽  
Jaroslav Holeček
Keyword(s):  
13C Nmr ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
The Other ◽  
13C Nmr Spectra ◽  
Other Hand ◽  
Carboxylic Esters ◽  
C Nmr ◽  
Oxygen Atoms

The 17O and 13C NMR spectra of eight geminal diacetates RCH(O(CO)CH3)2 derived from simple aldehydes have been measured. In contrast to the dicarboxylates R1R2E(O(CO)R3)2, where E = Si, Ge, or Sn, whose 17O NMR spectra only contain a single signal, and, on the other hand, in accordance with organic carboxylic esters, the 17O NMR spectra of the compound group studied always exhibit two well-resolved signals with the chemical shifts δ(17O) in the regions of 183-219 ppm and 369-381 ppm for the oxygen atoms in the groups C-O and C=O, respectively.

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