Substituent effects of phosphorus-containing groups on aromatic reactivity. Determination of substituent constants by 13C nuclear magnetic resonance spectroscopy

1977 ◽  
Vol 55 (21) ◽  
pp. 3681-3685 ◽  
Author(s):  
Tomasz A. Modro
Keyword(s):  
Substituent Effects ◽  
Resonance Spectroscopy ◽  
Benzene Derivatives ◽  
13C Nuclear Magnetic Resonance ◽  
Phosphorus Containing ◽  
Substituent Constants ◽  
Parameter Approach ◽  
Reactivity Determination ◽  
C Nmr

13C nmr spectra have been obtained for a series of benzene derivatives substituted with phosphorus-containing groups of the type PZ2, P(O)Z2, and P(S)Z2. Inductive and resonance substituent constants were determined from the shielding of meta and para carbon atoms according to the dual-substituent parameter approach. Possible mechanisms of substituent effects of PIII and PV derived functional groups are discussed and in some cases compared with effects of the analogous nitrogen derivatives.

scholarly journals Determination of the pKa of glucuronic acid and the carboxy groups of heparin by 13C-nuclear-magnetic-resonance spectroscopy

1991 ◽  
Vol 278 (3) ◽  
pp. 689-695 ◽  
Author(s):  
H M Wang ◽  
D Loganathan ◽  
R J Linhardt
Keyword(s):  
Uronic Acid ◽  
Model Compound ◽  
Molecular Size ◽  
Resonance Spectroscopy ◽  
Model Compounds ◽  
Pka Values ◽  
Carboxylate Groups ◽  
13C Nuclear Magnetic Resonance ◽  
Unambiguous Assignment

As part of our continuing studies on heparin, the present paper uses 13C-n.m.r. spectroscopy to examine the acidity of heparin's uronic acid carboxylate groups. Heparin contains three different uronic acids. In porcine mucosal heparin these account for approx. 91, 7 and 2 mol% of the total uronic acid residues. These are alpha-L-idopyranosyluronic acid 2-sulphate, beta-D-glucopyranosyluronic acid and alpha-L-idopyranosyluronic acid. The pKa values of their carboxylate groups were determined as 3.13 (using heparin), 2.79 (using heparin) and 3.0 (predicted by using model compounds) respectively. 18C-n.m.r. spectroscopy, performed at various pH values, provided a convenient method of simultaneously determining the pKa of multiple carboxylate groups, of similar acidity, within heparin D-Glucopyranosyluronic acid and heparin-derived di-, tetra- and hexa-saccharides were used as model compounds to determine pKa values of the different carboxy groups. The results suggested that molecular size had an effect on pKa. Unambiguous assignment of carboxy carbon resonances were accomplished through the use of two-dimensional n.m.r. spectroscopy. Finally, application of this method to the simplest model compound, D-glucopyranosyluronic acid, permitted the determination of the pKa of both its alpha- and beta-anomers.

Analysis of substituent and solvent effects on dissociation of N-phenylbenzenesulphonamides

1987 ◽  
Vol 52 (12) ◽  
pp. 2900-2908 ◽  
Author(s):  
Miroslav Ludwig ◽  
Oldřich Pytela ◽  
Helena Javůrková ◽  
Miroslav Večeřa
Keyword(s):  
Factor Analysis ◽  
Hydrogen Bonds ◽  
Model Equation ◽  
Substituent Effects ◽  
Regression Function ◽  
Reaction Centre ◽  
Solvent Dependence ◽  
Substituent Constants ◽  
Reaction Constants

The potentiometric titration in water, methanol, dimethyl sulphoxide, dimethylformamide, and acetonitrile has been used for determination of pK values of 13 N-arylbenzenesulphonamides. The validity of the Hammett and Yukawa-Tsuno models using several sets of substituent constants has been evaluated by the test to check adequacy of the regression function and by the factor analysis. It has been found that the substituent effects in solvents must be interpreted with regard to the experimental method used, solvent, set of the substituent constants, as well as the model equation ETR. The dependence of the Hammett reaction constants on the solvent has been analyzed and reveals a preferred stabilization of the conjugated base through hydrogen bonds. Direct conjugation of the reaction centre with the substituent and with different extent of the solvent-dependence with the 4-CN and 4-NO2 derivatives have been observed.

scholarly journals Chemical constituents of the physodes of brown algae. Characterization by 1H and 13C nuclear magnetic resonance spectroscopy of oligomers of phloroglucinol from Fucus vesiculosus (L.)

1977 ◽  
Vol 55 (9) ◽  
pp. 1575-1582 ◽  
Author(s):  
James S. Craigie ◽  
A. Gavin McInnes ◽  
Mark A. Ragan ◽  
John A. Walter
Keyword(s):  
Molecular Weight ◽  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Chemical Constituents ◽  
Fucus Vesiculosus ◽  
Resonance Spectroscopy ◽  
Low Molecular Weight ◽  
13C Nuclear Magnetic Resonance ◽  
C Nmr

Alcoholic extracts of Fucus vesiculosus contain small quantities of low molecular weight polyphenols derived from phloroglucinol and 2,2′,4,4′,6,6′-hexahydroxybiphenyl. 1H and 13C nmr were used to identify two of these as 4-(2′′,4′′,6′′-trihydroxyphenoxy)-2,2′,4′,6,6′-pentahydroxybiphenyl and 4-(2′′-(2′′′,4′′′,6′′′-trihydroxyphenoxy)-4′′,6′′-dihydroxyphenoxy)-2,2′,4′, 6,6′-pentanydroxybiphenyl.

Selective, reductive dechlorination of chlorodeoxy sugars. Structural determination of chlorodeoxy and deoxy sugars by 13C nuclear magnetic resonance spectroscopy

1976 ◽  
Vol 54 (23) ◽  
pp. 3783-3793 ◽  
Author(s):  
Walter A. Szarek ◽  
Aleksander Zamojski ◽  
Alan R. Gibson ◽  
Dolatrai M. Vyas ◽  
J. K. N. Jones
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Reductive Dechlorination ◽  
Potassium Hydroxide ◽  
Resonance Spectroscopy ◽  
Structural Determination ◽  
13C Nuclear Magnetic Resonance ◽  
Reduced Products

The reductive dechlorination of chlorodeoxy sugars by hydrogenation over Raney nickel in the presence of potassium hydroxide or triethylamine has been investigated; a selective dechlorination was observed in most cases with triethylamine. Several new, chlorodeoxy furanoid derivatives have been synthesized by the use of triphenylphosphine–carbon tetrachloride. 13C magnetic resonance spectroscopy has been employed for the assignment of structure to the chlorodeoxy sugars and the corresponding reduced products.

Stereoselective epimerization of pilocarpine in aqueous solution as determined by 13C nuclear magnetic resonance spectroscopy

1976 ◽  
Vol 54 (13) ◽  
pp. 2094-2100 ◽  
Author(s):  
George A. Neville ◽  
Fariza B. Hasan ◽  
Ian C. P. Smith
Keyword(s):  
Degradation Products ◽  
Parent Compound ◽  
Imidazole Ring ◽  
Alkaline Treatment ◽  
Resonance Spectroscopy ◽  
Open Chain ◽  
Similar Treatment ◽  
13C Nuclear Magnetic Resonance ◽  
Hydrolysis Of ◽  
C Nmr

Cleavage and recyclization of the lactone ring of pilocarpine (1) and of isopilocarpine (2) in D2O with varying pD have been studied by 13C nmr spectroscopy. Alkaline treatment (pD 10–13) results in rapid epimerization of pilocarpine to form isopilocarpine (28 ± 3% at 30 °C) and hydrolysis of the parent compound(s) to form the open chain pilocarpinate (isopilocarpinate). By contrast, isopilocarpine does not epimerize to pilocarpine under similar treatment. A mechanism is discussed for the epimerization of pilocarpine and the nonepimerization of the isopilocarpine is rationalized. pKa values of 5.7 and 8.5, respectively, have been determined for pilocarpinic acid and for the dissociation of the protonated quaternary nitrogen of the imidazole ring of pilocarpine. A basis for assay of degradation products in aqueous pilocarpine solutions utilizing differences in 13C chemical shift for C-8 is discussed.

Direct non-invasive observation of metabolism in living cells by 13C nuclear magnetic resonance spectroscopy

1980 ◽  
Vol 58 (17) ◽  
pp. 1839-1846 ◽  
Author(s):  
Gerardo Burton ◽  
Robert L. Baxter ◽  
J. Martyn Gunn ◽  
Philip J. Sidebottom ◽  
Paul E. Fagerness ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Anaerobic Metabolism ◽  
Aminolevulinic Acid ◽  
Living Cells ◽  
Resonance Spectroscopy ◽  
Whole Cells ◽  
Non Invasive ◽  
13C Nuclear Magnetic Resonance ◽  
C Nmr

Applications of 13C nmr in following the metabolism and fate of 13C enriched substrates in whole cells are described. Studies on the elaboration of coproporphyrinogens I (2a) and III (2b) from [5-13C]-δ-aminolevulinic acid (1) and [11-13C-porphobilinogen (PBG, 3), in Rhodopseudomonasspheroides and Propionibacteriumshermanii, respectively, the randomization of 13C from [3-13C]-propionate by P. shermanii, the biosynthesis of citrate, gentisalcohol (4), and patulin (5) from [2-13C]-acetate by Penicilliumurticae, and the anaerobic metabolism of [1-13C]-glucose in rabbit erythrocytes are reported.

Multinuclear (1H, 13C and 15N) Magnetic Resonance Spectroscopy and Substituent Effects on N-Phenoxyethylanilines

2002 ◽  
Vol 57 (2) ◽  
pp. 226-232 ◽  
Author(s):  
Jorge L. Jios ◽  
Gustavo P. Romanelli ◽  
Juan C. Autino ◽  
Damian Magiera ◽  
Helmut Duddeck
Keyword(s):  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Substituent Effect ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
The Other ◽  
Resonance Spectroscopy ◽  
Phenyl Rings ◽  
Substituent Constants

1H, 13C and 15N NMR spectra of twenty substituted N-phenoxyethylanilines 1-20 were completely and unambiguously assigned using a combination of both homo- and heteronuclear (gs-COSY), 1H detected heteronuclear one-bond (gs-HMQC) and long-range (gs- HMBC) gradient-selected correlation experiments. Correlations between chemical shifts and substituent constants are analyzed separately for both phenyl rings using variable substituents para to the fixed substituent -OCH2CH2NHC6H5 (series I) and -NHCH2CH2OC6H5 (series II), respectively. The correlation coefficient for chemical shifts vs. a linear combination of inductive and resonance substituent constants is high and improves when only the six values, corresponding to each para-monosubstituted series, were used. For nitrogen chemical shifts excellent linear dependences were obtained. The results show that the ethylene chain is not able to transmit the substituent effect from one aromatic ring to the other.

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