Additions and Corrections - The Primary Carbon Isotope Effect on the Ionization of Triphenylmethyl Chloride. Experimental Determination, Theoretical Justification, and Implications for Carbon Isotope Effects on Nucleophilic Substitution at Saturated Carbon.

1965 ◽  
Vol 87 (24) ◽  
pp. 5809-5810
Author(s):  
A. Kresge ◽  
N. Lichtin ◽  
K. Rao ◽  
R. Weston, Jr.
Keyword(s):  
Experimental Determination ◽  
Nucleophilic Substitution ◽  
Carbon Isotope ◽  
Isotope Effect ◽  
Isotope Effects ◽  
Theoretical Justification ◽  
Carbon Isotope Effect

Viewpoint: Carbon isotope effect predictions for enzymes involved in the primary carbon metabolism of plant leaves

2005 ◽  
Vol 32 (4) ◽  
pp. 277 ◽  
Author(s):  
Guillaume Tcherkez ◽  
Graham D. Farquhar
Keyword(s):  
Carbon Isotope ◽  
Isotope Effect ◽  
Carbon Metabolism ◽  
Citrate Synthase ◽  
Isotope Effects ◽  
Krebs Cycle ◽  
Equilibrium Reactions ◽  
Theoretical Predictions ◽  
Carbon Isotope Effect

Carbon isotope effects of enzymes involved in primary carbon metabolism are key parameters in our understanding of plant metabolism. Nevertheless, some of them are poorly known because of the lack of in vitro experimental data on purified enzymes. Some studies have focused on theoretical predictions of isotope effects. Here we show how quantum chemical calculations can be adapted for calculation of isotope effects for the Rubisco-catalysed carboxylation and oxygenation reactions and the citrate synthase reaction. The intrinsic isotope effect of the carboxylation by Rubisco appears to be much smaller than previously thought, being close to the overall isotope effect of the reaction that is, between 25 and 30 per mil. The same applies to the enzyme citrate synthase, that catalyses the first step of the Krebs cycle, with an isotope effect of around 23 per mil. Combined with the isotope effects of equilibrium reactions calculated with β-factors, the Krebs cycle then has an overall isotope effect that depletes organic acids in 13C.

scholarly journals Evidence for a major missing source in the global chloromethane budget from stable carbon isotopes

2019 ◽  
Vol 19 (3) ◽  
pp. 1703-1719 ◽  
Author(s):  
Enno Bahlmann ◽  
Frank Keppler ◽  
Julian Wittmer ◽  
Markus Greule ◽  
Heinz Friedrich Schöler ◽  
...  
Keyword(s):  
Carbon Isotope ◽  
Carbon Isotopes ◽  
Isotope Effect ◽  
Stable Carbon Isotopes ◽  
Tropical Rainforest ◽  
Isotope Effects ◽  
Stratospheric Ozone ◽  
Mixing Ratios ◽  
Promising Tool ◽  
Carbon Isotope Effect

Abstract. Chloromethane (CH3Cl) is the most important natural input of reactive chlorine to the stratosphere, contributing about 16 % to stratospheric ozone depletion. Due to the phase-out of anthropogenic emissions of chlorofluorocarbons, CH3Cl will largely control future levels of stratospheric chlorine. The tropical rainforest is commonly assumed to be the strongest single CH3Cl source, contributing over half of the global annual emissions of about 4000 to 5000 Gg (1 Gg = 109 g). This source shows a characteristic carbon isotope fingerprint, making isotopic investigations a promising tool for improving its atmospheric budget. Applying carbon isotopes to better constrain the atmospheric budget of CH3Cl requires sound information on the kinetic isotope effects for the main sink processes: the reaction with OH and Cl in the troposphere. We conducted photochemical CH3Cl degradation experiments in a 3500 dm3 smog chamber to determine the carbon isotope effect (ε=k13C/k12C-1) for the reaction of CH3Cl with OH and Cl. For the reaction of CH3Cl with OH, we determined an ε value of (-11.2±0.8) ‰ (n=3) and for the reaction with Cl we found an ε value of (-10.2±0.5) ‰ (n=1), which is 5 to 6 times smaller than previously reported. Our smaller isotope effects are strongly supported by the lack of any significant seasonal covariation in previously reported tropospheric δ13C(CH3Cl) values with the OH-driven seasonal cycle in tropospheric mixing ratios. Applying these new values for the carbon isotope effect to the global CH3Cl budget using a simple two hemispheric box model, we derive a tropical rainforest CH3Cl source of (670±200) Gg a−1, which is considerably smaller than previous estimates. A revision of previous bottom-up estimates, using above-ground biomass instead of rainforest area, strongly supports this lower estimate. Finally, our results suggest a large unknown CH3Cl source of (1530±200) Gg a−1.

Atomic Substitution And Carbon Isotope Effect In Superconducting MgCNi3

2006 ◽  
Author(s):  
T. Klimczuk ◽  
V. Gupta ◽  
M. Avdeev ◽  
J. D. Jorgensen ◽  
R. J. Cava
Keyword(s):  
Carbon Isotope ◽  
Isotope Effect ◽  
Carbon Isotope Effect ◽  
Atomic Substitution

Carbon isotope effect on dehydration of bicarbonate ion catalyzed by carbonic anhydrase

Biochemistry ◽  
1985 ◽  
Vol 24 (19) ◽  
pp. 5143-5147 ◽  
Author(s):  
Piotr Paneth ◽  
Marion H. O'Leary
Keyword(s):  
Carbonic Anhydrase ◽  
Carbon Isotope ◽  
Isotope Effect ◽  
Carbon Isotope Effect

Equilibrium carbon isotope effect on a decarboxylation reaction

1978 ◽  
Vol 80 (1) ◽  
pp. 155-160 ◽  
Author(s):  
Marion H. O'Leary ◽  
Crayton J. Yapp
Keyword(s):  
Carbon Isotope ◽  
Isotope Effect ◽  
Decarboxylation Reaction ◽  
Carbon Isotope Effect

A Carbon Isotope Effect in the Decarboxylation of the Anisoyloxy Radical

Nature ◽  
1963 ◽  
Vol 197 (4874) ◽  
pp. 1294-1295
Author(s):  
T. H. BATES ◽  
J. C. BEVINGTON
Keyword(s):  
Carbon Isotope ◽  
Isotope Effect ◽  
Carbon Isotope Effect

Correlation of isotope effects in substitution reactions with nucleophilicities. Secondary α-deuterium isotope effect in the iodide-131 exchange of methyl-d3 iodide

1967 ◽  
Vol 45 (18) ◽  
pp. 2023-2031 ◽  
Author(s):  
Stanley Seltzer ◽  
Andreas A. Zavitsas
Keyword(s):  
Nucleophilic Substitution ◽  
Isotope Effect ◽  
Isotope Effects ◽  
Substitution Reactions ◽  
Deuterium Isotope Effect ◽  
Nucleophilic Substitution Reactions ◽  
Leaving Group ◽  
The Difference

The secondary α-deuterium isotope effect in iodide-131 exchange of methyl-d3 iodide is kH/kD = 1.05 ± 0.01 in methanol and 1.10 ± 0.04 in water at 20°. A correlation of secondary α-deuterium and 13C effects, in bimolecular nucleophilic substitution reactions, with the difference of E values between nucleophile and leaving group is presented.

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