Secondary steric effects in 2,4,6-trialkylated acetophenones and nitrobenzenes: Dipole moments and 13C NMR spectra

1985 ◽  
Vol 50 (1) ◽  
pp. 208-214 ◽  
Author(s):  
Juraj Koudelka ◽  
David Šaman ◽  
Otto Exner
Keyword(s):  
Nmr Spectra ◽  
Dipole Moments ◽  
Steric Effects ◽  
13C Nmr Spectra ◽  
Variable Size ◽  
Anisotropic Polarizability ◽  
Steady Decrease ◽  
Alkyl Groups ◽  
Physical Quantities ◽  
C Nmr

Dipole moments of 2,4,6-trialkylated acetophenones (II) and bromobenzenes (III) with variable size of the alkyl groups were measured in two solvents. The main intention was to shed more light on the previous results with similarly substituted nitrobenzenes (I). The comparison reveals a steady decrease of the dipole moment with the increasing size of the alkyl group in all three series. In addition, there is a stronger effect of steric inhibition of mesomerism in the series II and a comparably strong effect of the anisotropic polarizability in I; the two cannot be distinguished on the basis of dipole moments. Similarly an analysis of 13C NMR shifts reveals at least two effects. In one of them the series I behaves like III, in the other like II. Summarizing, our results are in agreement with the conception of negligible conjugation of the nitro group but they do not contribute significantly to its evidence which is based mainly on other physical quantities.

13C NMR spectra of 1-aryl-ferrocenylethylenes

1986 ◽  
Vol 51 (3) ◽  
pp. 670-676 ◽  
Author(s):  
Eva Solčániová ◽  
Štefan Toma ◽  
Tibor Liptaj
Keyword(s):  
13C Nmr ◽  
Nmr Spectra ◽  
Substituent Effects ◽  
13C Nmr Spectra ◽  
Bridge Group ◽  
C Nmr ◽  
Electron Effects

13C NMR spectra of 18 ferrocene analogues of trans stilbenes (1-aryl-2-ferrocenylethylenes) were measured. It was found that bridge group weakens the transfer of the substituent electron effects into ferrocene nucleus, especially distinctly into 3',4'positions of cyclopentadienyl ring. The transfer of substituent effects into β-position of the bridge -CH=CH- is greater in derivatives studied by us than in stilbenes. Synthesis of 1-(4-dimethylaminophenyl)-2-ferrocenylethylene is described.

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.

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.

scholarly journals The NMR Spin Systems of Scutellaria 8β,13-Epoxy-neo-clerod-3-en-15,16-olides and Revision of 1H and 13C NMR Spectra Reported Data

2020 ◽  
Vol 15 (10) ◽  
pp. 1934578X2093378
Author(s):  
Josep Coll Toledano
Keyword(s):  
13C Nmr ◽  
Nmr Spectra ◽  
Spin Systems ◽  
13C Nmr Spectra ◽  
1H And 13C Nmr ◽  
Nmr Data ◽  
Reported Data ◽  
New Compounds ◽  
C Nmr ◽  
Shielding Effects

The present review of NMR spectroscopic structural elucidation data of new compounds isolated from Scutellaria species is focused on the title compounds, displaying a peculiar 13-spiro feature. It contains a compilation of 1H and 13C NMR data of these diterpenoids grouped by similar substitution patterns. Comparing shielding effects pointed out not only the identity of some compounds (already reported) but also potential misassignments and convenient revisions to get unambiguous structural proposals.

Nuclear Magnetic Resonance Studies on Aromatic Compounds, IV 13C NMR Spectra of Some Disulpho-substituted 1- and 2-Naphthols

1977 ◽  
Vol 32 (7) ◽  
pp. 818-820 ◽  
Author(s):  
Kauko Räisänen ◽  
Lauri H. J. Lajunen
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Aromatic Compounds ◽  
Nmr Spectra ◽  
Hydroxyl Group ◽  
Mesomeric Effect ◽  
13C Nmr Spectra ◽  
Magnetic Resonance Studies ◽  
Fine Splitting ◽  
Substituted 1 ◽  
C Nmr

The 13C NMR spectra of 1-hydroxynaphthalene-3,6-disulphonic, 1-hydroxynaphthalene- 3,8-disulphonic, 2-hydroxynaphthalene-3,6-disulphonic, and 2-hydroxynaphthalene-6,8-disulphonic acids were determined with and without noise-decoupling. The fine splitting caused by the long-range couplings pattern was used in the identification of the resonances lines of the 13C nuclei. The combined influence of the mesomeric effect of the hydroxyl group and that of the sulphonate groups have been discussed.

scholarly journals 1H- und C-NMR-Spektren von Methoxy-substituierten Äthylenen / 1H and 13C NMR Spectra of Methoxy-substituted Ethylenes

1976 ◽  
Vol 31 (1) ◽  
pp. 35-38 ◽  
Author(s):  
M. Herberhold ◽  
G. O. Wiedersatz ◽  
C. G. Kreiter
Keyword(s):  
Charge Distribution ◽  
Vinyl Ether ◽  
13C Nmr ◽  
Nmr Spectra ◽  
13C Nmr Spectra ◽  
1H And 13C Nmr ◽  
Methyl Vinyl ◽  
Methyl Vinyl Ether ◽  
Cis And Trans ◽  
C Nmr

The charge distribution in the methoxy -substituted olefins of the series ethylene, methyl vinyl ether, 1,1-dimethoxyethylene, cis- and trans-dimethoxyethylene, tetramethoxyethylene, is discussed on the basis of the 1H and 13C NMR spectra

Assignment techniques for 29Si NMR spectra of pertrimethylsilylated products. 29Si satellites in 13C NMR spectra measured with selective 29Si decoupling

1985 ◽  
Vol 50 (9) ◽  
pp. 2060-2064 ◽  
Author(s):  
Jaan Past ◽  
Jüri Puskar ◽  
Jan Schraml ◽  
Endel Lippmaa
Keyword(s):  
Nmr Spectra ◽  
29Si Nmr ◽  
13C Nmr Spectra ◽  
Difference Spectroscopy ◽  
Experimental Scheme ◽  
H Nmr ◽  
Correct Assignment ◽  
Sensitivity And Selectivity ◽  
29Si Nmr Spectra ◽  
C Nmr

It is shown that measurement of 29Si satellites in proton decoupled 13C NMR spectra with selective 29Si decoupling allows correct assignment of lines in 29Si NMR spectra of pertrimethylsilylated products. The experimental scheme, where selective decoupling and FID phase alternation are used (difference spectroscopy), has sufficient sensitivity and selectivity, provided the 29Si lines are well separated. The main advantage of the method is that it can be applied to compounds with unresolved 1H NMR spectra or with no protons in γ position to the silicon atom.

13C-NMR-Spektren einiger Acridon-Derivate [1] / 13C NMR Spectra of Some Acridone Derivatives [1]

1979 ◽  
Vol 34 (3) ◽  
pp. 516-519 ◽  
Author(s):  
I. Mester ◽  
D. Bergenthal ◽  
Zs. Rózsa ◽  
J. Reisch
Keyword(s):  
13C Nmr ◽  
Nmr Spectra ◽  
13C Nmr Spectra ◽  
Acridone Derivatives ◽  
C Nmr

Abstract The 13C NMR spectra of acridone derivatives 3-5, 8-12, melicopicine (14), melicopidine (15) and melicopine (16) are presented. The substituent parameters for OH and OCH3 groups in acridone derivatives have also been given.

scholarly journals Highly reactive, liquid diacrylamides via synergistic combination of spatially arranged curing moieties

2017 ◽  
Vol 13 ◽  
pp. 372-383 ◽  
Author(s):  
Maximilian Maier ◽  
Magnus S Schmidt ◽  
Markus Ringwald ◽  
Christoph P Fik
Keyword(s):  
Refractive Index ◽  
Mechanical Testing ◽  
Functional Groups ◽  
Nmr Spectra ◽  
Dsc Measurements ◽  
Alkyl Groups ◽  
Before And After ◽  
Reactive Liquid ◽  
Synergistic Combination ◽  
C Nmr

Six polymerizable N,N’-diacylamides containing spatially arranged N-acryl, N-allyl and/or N-alkyl groups were prepared via two-step syntheses and characterized by 1H/13C NMR-spectra, refractive index (RI) and viscosity measurements. Photo DSC measurements on activated samples provided reactivity parameters ∆H p, R p,max and t max, while FTIR spectra before and after curing elucidated the underlying polymerization mechanism. Mechanical testing of the obtained polymers exhibited gradual differences in network densities, depending on the intramolecular arrangement and number of functional groups. Overall, a general building principle for highly reactive, liquid diacrylamides via synergistic combination of optimally arranged functional groups could be identified. The highest possible level of intramolecular synergism was found for low viscous N,N'-diacryloyl-N,N'-diallyl-1,4-but-2-enediamine.

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.

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