29Si and 13C nmr spectra of trimethylsiloxy and hydroxy adamantanes reinvestigated at low concentration in deuteriochloroform solutions

1990 ◽  
Vol 55 (2) ◽  
pp. 452-459 ◽  
Author(s):  
Jan Schraml ◽  
Jan Čermák
Keyword(s):  
Nmr Spectra ◽  
Solvent Accessibility ◽  
Chemical Shifts ◽  
13C Nmr Spectra ◽  
Hydrogen Atoms ◽  
Adamantane Skeleton ◽  
Induced Changes ◽  
Trimethylsilyl Groups ◽  
C Nmr ◽  
Oxygen Atoms

29Si and 13C NMR chemical shifts are reported for mono- and bis(trimethylsiloxy)adamantanes as well as for mono- and dihydroxyadamantanes dissolved in deuteriochloroform. The chloroform induced changes in 29Si and 13C chemical shifts can be qualitatively accounted for by hydrogen-bonding considering basicity and solvent accessibility of oxygen atoms in the solute molecules. The steric effects observed on the 29Si shifts are not due to an interaction of the terminal hydrogen atoms of the trimethylsilyl groups but are due to proximity of two oxygen atoms on one cyclohexane ring of the adamantane skeleton.

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.

13C NMR spectra of hydroxy adamantanes additivity in 13C NMR spectra of dihydroxyadamantanes

1979 ◽  
Vol 44 (7) ◽  
pp. 2230-2237 ◽  
Author(s):  
Jan Schraml ◽  
Harald Jancke ◽  
Günter Engelhardt ◽  
Luděk Vodička ◽  
Josef Hlavatý
Keyword(s):  
13C Nmr ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Hydroxyl Groups ◽  
13C Nmr Spectra ◽  
Limited Information ◽  
Adamantane Skeleton ◽  
Cyclic Compounds ◽  
Intramolecular Hydrogen ◽  
C Nmr

The 13C NMR spectra of all monohydroxy and ditopic dihydroxy adamantane isomers were measured and the lines assigned. The numbers of the isomers and of the non-equivalent carbon atoms permitted a verification of the simple additivity of the shielding contributions of two hydroxyl groups on the rigid adamantane skeleton in the isomers without a possibility of a direct OH-OH interaction. If such interactions occur, deviations are found. The direction and magnitude of the deviations is in agreement with the current interpretation of 13C chemical shifts in other classes of cyclic compounds. It is concluded that the deviations are not caused by intramolecular hydrogen bonds. The deviations and the values of substituent chemical shifts offer some limited information about the origin of the shielding effects, especially of those dependent on stereochemistry and degree of substitution (γanti effect).

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.

29Si (and 13C) NMR spectra of all pertrimethylsilylated O-acetyl and O-benzoyl 1,6-anhydro-β-D-glucopyranose derivatives. A test of empirical assignment rules

1985 ◽  
Vol 50 (5) ◽  
pp. 1176-1183 ◽  
Author(s):  
Jan Schraml ◽  
Štefan Kučár ◽  
Jan Zelený ◽  
Václav Chvalovský
Keyword(s):  
13C Nmr ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
13C Nmr Spectra ◽  
Rule Based ◽  
C Nmr

All O-acetyl-1,6-anhydro-β-D-glucopyranoses and O-benzoyl-1,6-anhydro-β-D-glucopyranoses were pertrimethylsilylated. 29Si and 13C NMR spectra of the pertrimethylsilyl derivatives were measured and the 29Si chemical shifts were used to test two previously described empirical assignment rules. The rule based on the shielding order must be either restricted to the order δ(Si-2) > δ(Si-4) which holds for all the studied compounds or modified for each subclass of the studied compounds with the same O-substituents. The rule based on Hammett type dependence gives correct predictions for Si-3 chemical shifts. When both rules can be applied they yield identical assignments, in other cases they complement each other.

29Si and 13C NMR spectra of some alkyldiphenylchlorosilanes, alkyldiphenylsilanoles and bis(alkyldiphenylsilyl)chromates

1982 ◽  
Vol 47 (2) ◽  
pp. 603-612 ◽  
Author(s):  
Antonín Lyčka ◽  
Dobroslav Šnobl ◽  
Karel Handlíř ◽  
Jaroslav Holeček ◽  
Milan Nádvorník
Keyword(s):  
Electron Acceptor ◽  
13C Nmr ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Methyl Groups ◽  
Induction Effect ◽  
13C Nmr Spectra ◽  
Electronegative Substituent ◽  
Good Linear Correlation ◽  
C Nmr

29Si and 13C NMR spectra of alkyldiphenylchlorosilanes, alkyldiphenylsilanoles, and bis(alkyldiphenylsilyl)chromates (C6H5)2Si(R)X have been studied. The chemical shifts δ(29Si) are most affected by nature of the electronegative substituent X, i.e. Cl, OH or CrO3OSi(R). (C6H5)2. The δ(29Si) shifts due to effects of the substituents R can be correlated successfully with values of the Taft constants σ. Slopes of the correlation dependences have negative signs for all the groups of the studied compounds (increasing electron-acceptor ability of substituent R causes upfield shifts of δ(29Si), and their values decrease with increasing electronegativity of the substituent X (sensitivity of the δ(29Si) shifts due to sustituent R increases with increasing electronegativity of the substituent X). Methyl groups at γ-position of the chain of substituent R cause a diamagnetic shift of δ(29Si) by 0.6 to 3.3 ppm. The δ(13C) shifts depend little on nature of the substituent X. Chemical shifts δ(13C) of carbon atoms at α-, β-, and γ-positions of the substituent R with respect to silicon show a good linear correlation with the δ(13C) shifts of the corresponding carbon atoms in aliphatic hydrocarbons CH3R. Slopes of the correlation dependences of all the groups of studied compounds are close to 1, the intercepts for α- and β-positions are negative because of induction effect. Positive value of the intercepts for γ-positions reflects the influence of sterical γ-effect.

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.

1H and 13C NMR Spectra of Technically Important Sodium 1- and 2-Aminonaphthalenesulfonates

1993 ◽  
Vol 58 (6) ◽  
pp. 1378-1387 ◽  
Author(s):  
Josef Jirman
Keyword(s):  
13C Nmr ◽  
Sulfonic Acid ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Deuterium Oxide ◽  
Acid Group ◽  
Sulfonic Acid Group ◽  
13C Nmr Spectra ◽  
1H And 13C Nmr ◽  
C Nmr

The 1H and 13C NMR spectra of twenty-one technically important sulfonated 1- and 2-naphthylamines have been measured in deuterium oxide. The substituent chemical shifts (SCS) of a sulfonic acid group on naphthylamine skeleton have been calculated from the chemical shifts assigned.

scholarly journals 13C—NMR-Spektren und Bindungsverhältnisse von Ketenen / 13C—NMR-Spectra and Bonding Situation of Ketenes

1974 ◽  
Vol 29 (5-6) ◽  
pp. 393-398 ◽  
Author(s):  
Joachim Firl ◽  
Wolfgang Runge
Keyword(s):  
Carbon Atom ◽  
13C Nmr ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
13C Nmr Spectra ◽  
Terminal Carbon Atom ◽  
Central Carbon Atom ◽  
Central Carbon ◽  
C Nmr

18C-NMR spectra of alkyl- and arylsubstituted ketenes are reported1e. The terminal carbon atom resonances are found at extreme highfield positions ranging from 2.5 ppm to about 50 ppm. They are the most shielded sp2-carbon-atoms observed until now. The central carbon atom resonances appear from about 190 ppm to 206 ppm. From comparisons of the chemical shifts of the ketene carbon atoms with that of analogously substituted alienes and olefines conclusions concerning the bonding situation in ketenes are drawn.

Assignment of 1H and 13C NMR spectra by a combination of homo- and heteronuclear shift correlated two-dimensional NMR. Application to oligosaccharides related to arabinoxylane

1984 ◽  
Vol 49 (7) ◽  
pp. 1605-1616 ◽  
Author(s):  
Jan Schraml ◽  
Ján Hirsch ◽  
Eva Petráková ◽  
Eduard Krahé ◽  
Claus Bliefert
Keyword(s):  
Nmr Spectra ◽  
Chemical Shifts ◽  
Suitable Model ◽  
13C Nmr Spectra ◽  
Molecular Fragments ◽  
Model Compounds ◽  
1H And 13C Nmr ◽  
Complete Assignment ◽  
Other Information ◽  
C Nmr

It is shown that a combination of homo- and heteronuclear shift correlated 2 D NMR yields correct and complete assignment of 1H and 13C NMR spectra. The amount of the work necessary can be considerably reduced if some of the lines can be unambiguously assigned on the basis of other information or if suitable model compounds are available.The pattern of homonuclear cross-peaks is characteristic for molecular fragments and can be used with advantage to trace out the lines in the spectral regions with heavy overlap. The exactly assigned 13C chemical shifts of disaccharide and trisaccharide related to arabinoxylan agree satisfactorily with the shifts predicted according to the shifts found in the spectra of model mono- and disaccharides measured under the same conditions.

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