The molecular conformations of the stereoisomers of 4-methyl-5,6-benzo-2-oxo-1,3,2-dioxathiepin and of the 4,7-dimethyl derivative

1983 ◽  
Vol 61 (10) ◽  
pp. 2244-2253 ◽  
Author(s):  
A. Lachapelle ◽  
M. St-Jacques ◽  
A. C. Guimaraes ◽  
P. De Almeida
Keyword(s):  
Low Temperature ◽  
Ir Spectroscopy ◽  
Ir Spectra ◽  
Nmr Spectra ◽  
Dynamic Properties ◽  
Substituent Effects ◽  
Spectroscopy Analysis ◽  
Molecular Conformations ◽  
Methyl Group ◽  
Stretching Vibration

The conformational and dynamic properties of the stereoisomers of 4-methyl-5,6-benzo-2-oxo-1,3,2-dioxathiepin (5) and of the 4,7-dimethyl derivative (6) have been investigated by 1H and 13C dnmr methods, as well as by ir spectroscopy. Analysis of the nmr spectra at low temperature (−125 °C), together with the conformational interpretation of the stretching vibration bands of the S = O bond in the ir spectra, indicate that the most stable conformations detected for solutions in CHF2Cl are C-a (82%) and TB-t-Mec (18%) for 5a, TB-c-Mec, (96%) and TB-c-Mea, (4%) for 5b, C-a for 6a, TB-t-Mec, c-Mec, for 6b and C-e for 6c. The substituent effects of a methyl group at the benzylic position on both the conformational and dynamic properties of the seven-membered sulfite are discussed.

The molecular conformations of 8,11-dimethyl-5,6-benzo-2-oxo-1,3,2-dioxathiepin and 4,4-dimethyl-5,6-benzo-2-oxo-1,3,2-dioxathiepin

1985 ◽  
Vol 63 (8) ◽  
pp. 2185-2191 ◽  
Author(s):  
A. Lachapelle ◽  
M. St-Jacques
Keyword(s):  
Low Temperature ◽  
Ir Spectroscopy ◽  
Nmr Spectra ◽  
Room Temperature ◽  
Substituent Effects ◽  
Methyl Groups ◽  
Spectroscopy Analysis ◽  
Molecular Conformations ◽  
Conformational Properties ◽  
Stretching Vibrations

The conformational properties of 8,11-dimethyl-5,6-benzo-2-oxo-1,3,2-dioxathiepin (5) and of 4,4-dimethyl-5,6-benzo-2-oxo-1,3,2-dioxathiepin (6) have been investigated using 1H and 13C dnmr as well as ir spectroscopy. Analysis of low temperature nmr spectra (down to −148 °C) and of S=O stretching vibrations in room temperature ir spectra indicates that the most stable conformations detected for solutions in CHF2Cl/CD2Cl2 (80:20) are TB (83%) and C-a (17%) for 5 and only the TB 7 for 6. Substituent effects of methyl groups at the peri and the benzylic positions on the conformational properties of the seven-membered sulfites are discussed.

Influence of KBr conditioning on the infrared hydroxyl-stretching region of saponites

Clay Minerals ◽  
1999 ◽  
Vol 34 (3) ◽  
pp. 439-445 ◽  
Author(s):  
M. Pelletier ◽  
L. J. Michot ◽  
O. Barrès ◽  
B. Humbert ◽  
S. Petit ◽  
...  
Keyword(s):  
Ir Spectroscopy ◽  
Ir Spectra ◽  
Clay Minerals ◽  
Diffuse Reflectance ◽  
Layer Charge ◽  
Tetrahedral Sheet ◽  
Stretching Vibration ◽  
Sheet Charge

AbstractIn order to assess the influence of tetrahedral sheet charge on the hydroxyl-stretching vibration in clay minerals, a series of synthetic Na-saponites, with increasing layer charge, was studied by infrared (IR) spectroscopy. When recorded after KBr dilution either in transmission or diffuse reflectance, the IR spectra exhibit a component at ~3710 cm-1, the intensity of which increases linearly with increasing layer charge. When experiments are carried out without any dilution of the samples, this component is not observed, suggesting a Na+/K+ exchange upon mixing of the sample with KBr. The spectra obtained for K-saponite confirm this exchange. This shows that the dilution procedure can lead to serious misinterpretations of IR spectra in the OH-stretching region.

Thermogravimetric, infrared and mass-spectroscopic analysis of the desorption of methanol, propan-1-ol, propan-2-ol and 2-methylpropan-2-ol from montmorillonite

Clay Minerals ◽  
1993 ◽  
Vol 28 (1) ◽  
pp. 123-137 ◽  
Author(s):  
C. Breen ◽  
J. J. Flynn ◽  
G. M. B. Parkes
Keyword(s):  
Thermogravimetric Analysis ◽  
Low Temperature ◽  
Ir Spectroscopy ◽  
Ir Spectra ◽  
Spectral Data ◽  
Spectroscopic Analysis ◽  
Variable Temperature ◽  
Trivalent Cation ◽  
Mass Spectral Data ◽  
Mass Spectral

AbstractThe desorption of methanol (MeOH), propan-1-ol (n-PrOH), propan-2-ol (i-PrOH) and 2-methylpropan-2-ol (t-BuOH) from Na+-, Ca2+-, Al3+-, Cr3+- and Fe3+-exchanged montmorillonite has been studied using variable temperature infrared (IR) spectroscopy and thermogravimetric analysis (TGA). Alcohol-saturated trivalent cation (M3+) exchanged samples exhibit maxima in the derivative thermograms at 20 and 110°C (MeOH), 30 and 160°C (n-PrOH), 20 and 110°C (i-PrOH) and 20, 55 and 80°C (t-BuOH). Alcohol-saturated Na+ and Ca2+-exchanged montmorillonite samples exhibit maxima at higher temperatures in the i-PrOH (20 and 140°C) and t-BuOH (30, 90 and 110°C) desorption profiles but at the same temperatures for MeOH and n-PrOH. Mass spectroscopic analysis of the vapours desorbed from the alcohol-treated samples show that the low-temperature maxima in the alcohol desorption from the M3+-exchanged clays are due to unchanged alcohol, whilst those occurring at 80°C (t-BuOH), 110°C (i-PrOH) and 160°C (n-PrOH) are due, in the main, to alkene produced from the intramolecular dehydration of the respective alcohol. Changes in the IR spectra of the adsorbed alcohols occur at temperatures which are in accord with the mass spectral data. No mass spectral evidence was found for the formation of dialkylethers via the competing intermolecular process but dimerisation and oligomerisation of t-BuOH were observed.

2-[N,N-Bis(trimethylstannyl)amino]pyridine and Bis[N-(N-trimethyIsiIyI- 2-aminopyridyI)]dimethyltin - Intramolecular N-Sn Co-ordination

1999 ◽  
Vol 54 (9) ◽  
pp. 1165-1169 ◽  
Author(s):  
Bernd Wrackmeyer ◽  
Saqib Alib ◽  
Wolfgang Storch ◽  
Martina Vosteen
Keyword(s):  
Nmr Spectroscopy ◽  
Low Temperature ◽  
Nmr Spectra ◽  
Pyridine Ring ◽  
Methyl Group ◽  
Nmr Parameters

2-[N,N-Bis(trimethylstannyl)amino]pyridine (1), bis[N-(N-trimethylsilyl-2-aminopyridyl)]- dimethyltin (2) and bis[N-(N-trimethylsilyl-2-amino-3-methyl-pyridyl)]dimethyltin (3) were prepared and characterized by 1H, 13C, l5N, 29Si and 119Sn NMR spectroscopy. In the case of 1, intramolecular pyridine-N-Sn co-ordination was established by the low temperature 119Sn NMR spectra which show two resonance signals, one for a penta-co-ordinate and one for a tetra-co-ordinate tin site. In the cases of 2 and 3, intramolecular pyridine-N-Sn co-ordination follows conclusively from 13C, 15N and 119Sn NMR parameters. In contrast with the known behaviour of the corresponding trimethyltin derivative, the methyl group in 3-position of the pyridine ring does not prevent this type of co-ordination in 3.

The conformational properties of seven-membered heterocycles: 1,3-dioxacyclohept-5-ene and its 2-substituted derivatives

1981 ◽  
Vol 59 (15) ◽  
pp. 2283-2289 ◽  
Author(s):  
R. St-Amour ◽  
M. St-Jacques
Keyword(s):  
Low Temperature ◽  
Dynamic Properties ◽  
Substituent Effects ◽  
Dynamic Processes ◽  
Stable Conformation ◽  
Spectral Changes ◽  
Conformational Properties ◽  
C Nmr

1,3-Dioxacycloheptene and its 2-CH3, 2-OCH3, 2-t-Bu, and 2,2-dimethyl derivatives were studied by 1H and 13C dnmr methods. Substituent effects and the interpretation of spectral changes in 13C nmr at low temperature allow the determination of the most stable conformation of these compounds (TB for 1–4b and C for 5b) and the characterization of the dynamic processes observed for 2b, 4b, and 5b. The differences between the conformational and dynamic properties of the above compounds and their benzo analogs are rationalized in terms of different torsional interactions in the two series.

Synthetic and Spectroscopic Studies on N-(i,j-Disubstituted Phenyl)-4- Substituted Benzenesulphonamides, 4-X’C6H4SO2NH(i,j-X2C6H3), where X’ = H, CH3, C2H5, F, Cl or Br; i, j = 2, 3; 2, 4; 2, 5; 2, 6 or 3, 4; and X = CH3 or Cl

2005 ◽  
Vol 60 (1-2) ◽  
pp. 113-120 ◽  
Author(s):  
Mahesha Shetty ◽  
B. Thimme Gowda
Keyword(s):  
General Formula ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Spectroscopic Studies ◽  
Methyl Group ◽  
Methods Of Calculation ◽  
Benzene Rings ◽  
Stretching Vibrations ◽  
C Nmr

Fifty four N-(i,j-disubstituted phenyl)-4-substituted benzenesulphonamides of the general formula 4-X’C6H4SO2NH(i,j-X2C6H3), where X’ = H, CH3, C2H5, F, Cl or Br; i,j = 2,3; 2,4; 2,5; 2,6 or 3, 4; and X = CH3 or Cl, are prepared and characterized and their infrared, 1H and 13C NMR spectra in solution are studied. The N-H stretching vibrations νN−H absorb in the range 3305 - 3205 cm−1, while the asymmetric and symmetric SO2 vibrations vary in the ranges 1377 - 1307 cm−1 and 1184 - 1128 cm−1, respectively. The N-(i,j-disubstituted phenyl)-4-substituted benzenesulphonamides show C-S, S-N and C-N stretching vibrations in the ranges 844 - 800 cm−1, 945 - 891 cm−1 and 1309 - 1170 cm−1, respectively. The compounds do not exhibit particular trends in the variation of these frequencies on substitution either at ortho or meta positions with either a methyl group or Cl. The observed 1H and 13C chemical shifts ofare assigned to protons and carbon atoms of the two benzene rings. Incremental shifts of the ring protons and carbon atoms due to -SO2NH(i,j-X2C6H3) groups in C6H5SO2NH(i,j-X2C6H3) and 4-X’C6H4SO2NH- groups in 4-X’C6H4SO2NH(C6H*) are computed and employed to calculate the chemical shifts of the ring protons and carbon atoms in the substituted compounds 4-X’C6H4SO2NH(i,j-X2C6H3). The different methods of calculation lead to almost the same values in most cases and agree well with the observed chemical shifts, indicating the validity of the principle of additivity of the substituent effects with chemical shifts in these compounds.

Hydrolyse des dérivés de cyclopropylidène-3 propyle. Structure et stéréochimie des alcools précurseurs et des produits résultant de l'hydrolyse

1981 ◽  
Vol 59 (7) ◽  
pp. 1089-1095 ◽  
Author(s):  
Robert Faure ◽  
Gilbert Leandri ◽  
Alain Meou
Keyword(s):  
Ir Spectroscopy ◽  
Nmr Spectra ◽  
Molecular Conformation ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
H Nmr ◽  
Hydrolysis Products ◽  
Hydrolysis Of ◽  
C Nmr

The 13C nmr spectra of 14 β-cyclopropylidenic alcohols 1 have been determined:[Formula: see text]All the chemical shifts were assigned and the substituent effects are discussed as a function of molecular conformation. The stereochemistry of two diastereoisomers of alcohols 1e (R1 = R3 = H; R2 = R4 = CH3) and 1k (R3 = H; R1 = R2 = R4 = CH3) was established from ir spectroscopy and 1H nmr results.The 13C nmr spectra of products arising from hydrolysis of 3-cyclopropylidene propanol 1a and 4-cyclopropylidene 2-butanol 1b tosylates have been also recorded. The analysis of these data enables us to establish unambiguously the structure and the stereochemistry of the hydrolysis products.

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.

Sign in / Sign up

Export Citation Format

Share Document