Silicon-29 NMR Spectra of tert-Butyldimethylsilyl and Trimethylsilyl Derivatives of Some Non-Rigid Diols

1997 ◽  
Vol 62 (5) ◽  
pp. 761-768 ◽  
Author(s):  
Magdalena Kvíčalová ◽  
Vratislav Blechta ◽  
Krzysztof Kobylczyk ◽  
Ryszard Piekos ◽  
Jan Schraml
Keyword(s):  
Nmr Spectra ◽  
Chemical Shifts ◽  
Independent Study ◽  
Bulky Substituent ◽  
New Correlation ◽  
Proton Donors ◽  
Experimental Errors ◽  
Trimethylsilyl Derivatives ◽  
Intramolecular Hydrogen ◽  
Derivatives Of

29Si NMR spectra of trimethylsilyl (TMS) and tert-butyldimethylsilyl (TBDMS) derivatives of selected diols were measured under standardized conditions (i.e., in diluted CDCl3 solutions). Application of the recently reported correlation between the chemical shifts in TMS and TBDMS derivatives revealed considerable and systematic deviations which exceeded experimental errors and error estimates from the correlation. Two possible explanations of the deviations are considered: interaction between the two bulky substituent groups and invalidity of the reported correlation for simple hydroxy derivatives. An independent study of analogous derivatives of monohydroxy compounds has shown that the linear correlation holds but the slope and intercept are significantly different from those reported previously on the basis of a study of amino acid derivatives. The data obtained for the diol derivatives fit the new correlation very well and no indication of an interaction between the bulky TBDMS groups was noticed. However, deviations do occur in branched diol derivatives in which branching reduces accessibility of the oxygen atoms surface to associate with proton donors. The largest deviation was found when intramolecular hydrogen bond was formed.

Routine use of inept technique for measurements of 29Si NMR spectra of trimethylsilyl derivatives

1983 ◽  
Vol 48 (12) ◽  
pp. 3402-3406 ◽  
Author(s):  
Jan Schraml
Keyword(s):  
Nmr Spectra ◽  
Chemical Shifts ◽  
29Si Nmr ◽  
Practical Applications ◽  
Unknown Structure ◽  
29Si Nmr Spectra ◽  
Standard Set ◽  
Trimethylsilyl Derivatives ◽  
Low Sensitivity ◽  
Derivatives Of

Low sensitivity of 29Si NMR, slow 29Si relaxation, and negative Overhauser effect severly limit practical applications of 29Si NMR. The need for the large amount of the sample or of spectrometer time is dramatically reduced if the spectra can be recorded by INEPT technique. It is shown that a standard set of acquisition parameters allows routine measurements of proton decoupled 29Si NMR spectra by INEPT technique in trimethylsilyl derivatives of organic compounds with unknown structure. The INEPT technique makes measurements of 29Si chemical shifts from as litle as 20μmol of compound practical.

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.

29Si-Kernresonanzuntersuchungen an N-Trimethylsilyl-substituierten Aminen und Amiden / 29Si Nuclear Magnetic Resonance Studies on N-Trimethylsilyl Derivatives of Amines and Amides

1977 ◽  
Vol 32 (2) ◽  
pp. 163-166 ◽  
Author(s):  
B. Heinz ◽  
H. C. Marsmann ◽  
U. Niemann
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Aromatic Amines ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Electronic Charge ◽  
Magnetic Resonance Studies ◽  
Basic Character ◽  
Silyl Derivatives ◽  
Trimethylsilyl Derivatives ◽  
Derivatives Of

The 29Si chemical shifts of several trimethyl silyl derivatives of amines and amides are measured and compared to other chemical and theoretical properties such as the basicities or the electronic charge on the nitrogen or the hydrogen of the N-H group of the amine or the amide. Whereas the 29Si chemical shift of saturated amines can be rationalized in terms of substituent effects, the shifts of aromatic amines show some dependency on the basic character of the amine. There seems to be little correlation between 29Si chemical shifts and electronic charge, but there is a similarity of 29Si with 1H chemical shifts of the NH group, which is interpreted as depending on anisotropy effects.

ChemInform Abstract: Silicon-29 NMR Spectra of tert-Butyldimethylsilyl and Trimethylsilyl Derivatives of Some Non-Rigid Diols.

ChemInform ◽  
2010 ◽  
Vol 28 (39) ◽  
pp. no-no
Author(s):  
M. KVICALOVA ◽  
V. BLECHTA ◽  
K. KOBYLCZYK ◽  
R. PIEKOS ◽  
J. SCHRAML
Keyword(s):  
Nmr Spectra ◽  
Trimethylsilyl Derivatives ◽  
Derivatives Of

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).

Silicon-29 NMR Spectra of Trimethylsilylated Alcohols

1997 ◽  
Vol 62 (5) ◽  
pp. 816-820 ◽  
Author(s):  
Magdalena Kvíčalová ◽  
Jan Čermák ◽  
Vratislav Blechta ◽  
Jan Schraml
Keyword(s):  
Chemical Shift ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Steric Effects ◽  
Almost All ◽  
Derivatives Of ◽  
Related Compounds ◽  
Tms Derivatives

29Si NMR spectra of trimethylsilyl (TMS) derivatives of 26 simple alcohols were measured under standardized conditions (i.e., in sufficiently diluted deuteriochloroform solutions). Due to association with the solvent the chemical shifts are in almost all cases larger than those reported earlier for different solutions. This observation is in agreement with the proposed mechanism of steric effects as being due to sterically controlled association with the solvent. The use of chloroform as a solvent enhances steric effects but at the same time it can reduce small differences due to polar effects in closely related compounds. In the studied class of compounds the gross dependence of the chemical shift on polar effects is not substantially affected by the change of the solvent.

Assignment of the Absolute Configuration of Polyfunctional Compounds

2015 ◽  
Author(s):  
Josi M. Seco ◽  
Emilio Quiqoa ◽  
Ricardo Riguera
Keyword(s):  
Absolute Configuration ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Single Step ◽  
Point Of View ◽  
Hydroxyl Groups ◽  
Oh Groups ◽  
Polyfunctional Compounds ◽  
The Absolute ◽  
Derivatives Of

From a practical point of view, the assignment of the absolute configuration of sec/sec 1,2- and 1,n-diols does not require the separate derivatization (two different steps with the CDA of choice) of each one of the two hydroxyl groups present in the substrate; on the contrary, it can be carried out by simultaneous derivatization of the two hydroxyls (a single step), leading to the corresponding bis-(R)- and bis-(S)-CDA esters [13, 59–61]. The most used CDAs are 9-AMA and MPA [59, 60], although 1-NMA, 2-NMA, and MTPA are also appropriate [59, 60]. This assignment has an important difference compared to that of monofunctionalized compounds [15]; this is due to the presence in the bis-(R)- and bis-(S)-derivatives of two CDA units that produce distributions of ΔδRS and ΔδSR signs that do not follow the trends found in monoderivatized compounds [13, 15, 82]. This means that the NMR spectra of the bis-CDA derivatives cannot be interpreted as if they had originated from two isolated mono-CDA derivatives [82]. Thus, the correlations described for secondary alcohols [35–39] cannot be applied to diols [59–61] because the chemical shifts and ΔδRS values result from the combination of the anisotropic effects—usually shielding—from the two CDA units and not from a single unit, as happens with monoalcohols. A result of the combination of aromatic shielding effects [59, 60] in diols is that the diagnostic protons/signals for assignment are not always the same as in isolated monoalcohols (i.e., L1/L2). For instance, in acyclic syn-1,2-diols, the diagnostic signals [59, 60] are those corresponding to the protons at the alpha positions of the OH groups (i.e., the hydrogens linked directly to the asymmetric carbons) Hα(R1) and Hα(R2) exclusively. On the other hand, in acyclic anti-1,2-diols, the diagnostic signals are from Hα(R1)/Hα(R2) together with those from R1 and R2. As in the case of monofunctional compounds, the assignment consists [13, 59, 60] in the preparation of two bis-CDA derivatives from the two enantiomers of the chosen CDA, followed by comparison of the corresponding NMR spectra and calculation of the ΔδRS (or ΔδSR in the case of MTPA) signs for Hα(R1), R1, Hα(R2), and R2.

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.

scholarly journals Preparation and NMR properties of derivatives of arylamino-methylidene malonic acid and pentane-2,4-dione

2013 ◽  
Vol 6 (1) ◽  
pp. 73-81 ◽  
Author(s):  
Denisa Tarabová ◽  
Viktor Milata ◽  
Jiří Hanusek
Keyword(s):  
Malonic Acid ◽  
13C Nmr ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
13C Nmr Spectra ◽  
Kinetic Measurements ◽  
Ethyl Malonate ◽  
Derivatives Of ◽  
Nmr Properties

Abstract A set of 22 anilinomethylidene derivatives (13 new ones) of di(m)ethyl malonate, malononitrile and pentane-2,4-dione with various substituents in position 4- and 3-, respectively were prepared to study the characteristic influence of these substituents and solvents on chemical shifts in 13C NMR spectra and like reference compounds for kinetic measurements.

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