Aryl Carbanions. A 13C Nuclear Magnetic Resonance Study of Deuterium Exchange in Acenaphthenes and Related Aromatic Hydrocarbons

1973 ◽  
Vol 51 (17) ◽  
pp. 2884-2892 ◽  
Author(s):  
D. H. Hunter ◽  
J. B. Stothers
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Exchange Rates ◽  
Aromatic Hydrocarbons ◽  
Nuclear Magnetic Resonance Study ◽  
Deuterium Exchange ◽  
Hydrogen Deuterium Exchange ◽  
Magnetic Resonance Study ◽  
Ring Strain ◽  
13C Nuclear Magnetic Resonance ◽  
Hydrogen Deuterium

The base-catalyzed hydrogen–deuterium exchange rates for the aromatic and benzylic centers in acenaphthene, 2,3-dihydrophenalene, 1,8-dimethylnaphthalene, 1,1,2,2,-tetramethylacenaphthene, and diphenylmethane have been determined using 13C n.m.r. The exchange rates serve as a probe of carbanion stability and reactivity, clearly indicating the importance of ring strain effects on carbanion stability.

Nuclear magnetic resonance studies. XXXII. Rearrangement, isomerization, and deuterium exchange via β-enolization in bicyclooctenones. A 2H nuclear magnetic resonance study

1978 ◽  
Vol 56 (10) ◽  
pp. 1342-1347 ◽  
Author(s):  
A. K. Cheng ◽  
J. B. Stothers
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Nuclear Magnetic Resonance Study ◽  
Deuterium Exchange ◽  
Hydrogen Deuterium Exchange ◽  
Group Comparison ◽  
Magnetic Resonance Study ◽  
Hydrogen Deuterium ◽  
Derivatives Of ◽  
Nuclear Magnetic

The equilibration of the α,α -diniethyl derivatives of bicyclo[2.2.2]octenone, bicyclo[3.2.1]-oct-2-en-6-one, and its Δ3 isomer has been examined at 155 and 185 °C in tert-BuO−/tert-BuOH. Using 2Hmr spectroscopy the rates and stereoselectivity of hydrogen–deuterium exchange in each of these ketones have been determined for equilibrations with tert-BuOD as solvent. The relative reactivities for exchange at the allylic and vinylic sites compared to the analogous results for the corresponding olefins reveal a significant activating effect of the carbonyl group. Comparison of the data with those for the corresponding saturated ketones shows that the double bond enhances the rate of isomerization appreciably and increases the bias of the equilibrium toward the [3.2.1] skeleton.

13C nuclear magnetic resonance study of cyclodipeptides containing 13C enriched hydrophobic amino acids

1980 ◽  
Vol 45 (2) ◽  
pp. 482-490 ◽  
Author(s):  
Jaroslav Vičar ◽  
François Piriou ◽  
Pierre Fromageot ◽  
Karel Bláha ◽  
Serge Fermandjian
Keyword(s):  
Amino Acids ◽  
Nuclear Magnetic Resonance ◽  
Nuclear Magnetic Resonance Study ◽  
Coupling Constants ◽  
Side Chain ◽  
Amino Acid Residues ◽  
Magnetic Resonance Study ◽  
Side Chain Conformation ◽  
13C Nuclear Magnetic Resonance ◽  
Hydrophobic Amino Acids

The diastereoisomeric pairs of cyclodipeptides cis- and trans-cyclo(Ala-Ala), cyclo(Ala-Phe), cyclo(Val-Val) and cyclo(Leu-Leu) containing 85% 13C enriched amino-acid residues were synthesized and their 13C-13C coupling constants were measured. The combination of 13C-13C and 1H-1H coupling constants enabled to estimate unequivocally the side chain conformation of the valine and leucine residues.

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