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 NMR spectra of trimethylsilyl andtert-butyldimethylsilyl derivatives of purines and pyrimidines

1998 ◽  
Vol 36 (1) ◽  
pp. 55-63 ◽  
Author(s):  
Jan Schraml ◽  
Magdalena Kvíčalová ◽  
Vratislav Blechta ◽  
Roman Řeřicha ◽  
Jef Rozenski ◽  
...  
Keyword(s):  
Nmr Spectra ◽  
29Si Nmr ◽  
29Si Nmr Spectra ◽  
Derivatives Of ◽  
Purines And Pyrimidines

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.

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.

The role of electronic and steric effects in 29Si-NMR spectra of compounds with Si-O-C group

1981 ◽  
Vol 46 (2) ◽  
pp. 377-390 ◽  
Author(s):  
Jan Schraml ◽  
Václav Chvalovský ◽  
Märt Mägi ◽  
Endel Lippmaa
Keyword(s):  
Nmr Spectra ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
29Si Nmr ◽  
Methyl Group ◽  
29Si Nmr Spectra ◽  
Back Bonding ◽  
Electron Withdrawal ◽  
Electronic And Steric Effects

29Si-NMR chemical shifts are presented for several classes of compounds of general formula (CH3)4-n-mClnSi(OR)m (for n =0 m = 1-4 and for n = 1-3, m = 1). In most of the classes the shifts correlate linearly with polar constants of the substituents R or with Del Re net atomic charges on the silicon. The slopes in these correlations are all positive (i.e. the shielding decreases with electron withdrawal) and decrease with increasing n or m (i.e. the sensitivity of silicon shielding to substituent effects decreases with increasing number of electronegative substituents bonded to the silicon). This finding contradicts the available quantitative theories but can be accounted for by the qualitative model which considers back-bonding to silicon. Each methyl group in the γ position causes' a diamagnetic shift of 2 to 3 ppm, depending on the values of m and n, the effects are additive. Compounds with some heteroatoms in the γ position (R = CH2Cl, CH2Si(CH3)3, but not R = CH2Ge(CH3)3) behave anomalously, the origin of the anomalous shifts could not be ascertained.

17O, 13C, and 29Si NMR spectra of some acyloxy- and diacetoxysilanes and acetoxygermanes

1986 ◽  
Vol 51 (11) ◽  
pp. 2582-2589 ◽  
Author(s):  
Antonín Lyčka ◽  
Jaroslav Holeček ◽  
Karel Handlíř ◽  
Josef Pola ◽  
Václav Chvalovský
Keyword(s):  
Periodic System ◽  
Time Scale ◽  
Nmr Spectra ◽  
Group Element ◽  
29Si Nmr ◽  
Carboxyl Group ◽  
29Si Nmr Spectra ◽  
Oxygen Atoms

The 17O, 13C, and 29Si NMR spectra of (CH3)3SiOC(O)R, CH3(XCH2)Si(OC(O)CH3)2, and R3GeOC(O)CH3 compounds are reported. In the 17O NMR spectra at 350 K the only signal is observed with the two latter series, but two well-resolved signals are displayed with the (CH3)3SiOC(O)R compounds. The equivalence of both oxygen atoms in carboxyl group on the NMR time scale is discussed from the viewpoint of a possible coordination of the oxygen atoms to the IVB group element of the periodic system.

scholarly journals 29Si NMR Chemical Shifts in Crystalline and Amorphous Silicon Nitrides

Materials ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 1646 ◽  
Author(s):  
Ilia Ponomarev ◽  
Peter Kroll
Keyword(s):  
Silicon Nitride ◽  
Amorphous Silicon ◽  
Density Functional ◽  
Chemical Shifts ◽  
29Si Nmr ◽  
Hydrogenated Silicon ◽  
Nmr Chemical Shifts ◽  
Nmr Data ◽  
29Si Nmr Spectra ◽  
The Impact

We investigate 29Si nuclear magnetic resonance (NMR) chemical shifts, δiso, of silicon nitride. Our goal is to relate the local structure to the NMR signal and, thus, provide the means to extract more information from the experimental 29Si NMR spectra in this family of compounds. We apply structural modeling and the gauge-included projector augmented wave (GIPAW) method within density functional theory (DFT) calculations. Our models comprise known and hypothetical crystalline Si3N4, as well as amorphous Si3N4 structures. We find good agreement with available experimental 29Si NMR data for tetrahedral Si[4] and octahedral Si[6] in crystalline Si3N4, predict the chemical shift of a trigonal-bipyramidal Si[5] to be about −120 ppm, and quantify the impact of Si-N bond lengths on 29Si δiso. We show through computations that experimental 29Si NMR data indicates that silicon dicarbodiimide, Si(NCN)2 exhibits bent Si-N-C units with angles of about 143° in its structure. A detailed investigation of amorphous silicon nitride shows that an observed peak asymmetry relates to the proximity of a fifth N neighbor in non-bonding distance between 2.5 and 2.8 Å to Si. We reveal the impact of both Si-N(H)-Si bond angle and Si-N bond length on 29Si δiso in hydrogenated silicon nitride structure, silicon diimide Si(NH)2.

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