Unusually large deuterium isotope effect in the acid-catalyzed cis-trans isomerization of a diene-iron tricarbonyl complex

1975 ◽  
Vol 97 (4) ◽  
pp. 907-908 ◽  
Author(s):  
Thomas H. Whitesides ◽  
James P. Neiland
Keyword(s):  
Isotope Effect ◽  
Deuterium Isotope Effect ◽  
Tricarbonyl Complex ◽  
Trans Isomerization ◽  
Acid Catalyzed ◽  
Iron Tricarbonyl

EFFECT OF PRESSURE ON THE ACID-CATALYZED ENOLIZATION OF ACETONE AND ACETOPHENONE IN VARIOUS ETHANOL–WATER SOLVENTS. ORIGIN OF THE ENTHALPY–ENTROPY COMPENSATION EFFECT

1964 ◽  
Vol 42 (8) ◽  
pp. 1835-1850 ◽  
Author(s):  
B. T. Baliga ◽  
E. Whalley
Keyword(s):  
Isotope Effect ◽  
Atmospheric Pressure ◽  
Compensation Effect ◽  
Constant Pressure ◽  
Constant Volume ◽  
Deuterium Isotope Effect ◽  
Effect Of Pressure ◽  
Effect Of Solvent ◽  
Acid Catalyzed ◽  
Ethanol In Water

The effect of pressure, temperature, and solvent composition on the rate of the acid-catalyzed enolization of acetone and acetophenone, and the solvent deuterium isotope effect for the enolization of acetophenone, have been measured by following the iodination. The solvent deuterium isotope effect [Formula: see text] for the enolization of acetophenone in 16.2% w/w ethanol–water is 2.50 ± ~0.05, which undoubtedly proves that there is a pre-equilibrium proton transfer. The effect of solvent in the range water to 33.4% w/w ethanol in water on the rate of enolization of both acetone and acetophenone is small at atmospheric pressure, but is about four times larger at 3 kbar. This cannot be explained on simple electrostatic grounds, and indicates that any simple electrostatic explanation of the solvent effect at atmospheric pressure is invalid. The volumes of activation for the enolizations are strongly dependent on the solvent, that for acetone varying from −2.l ± ~0.5 to −6.9 ± ~ 0.7 cm3 mole−1 between solvents water and 33.4% w/w ethanol in water.An examination has been made of the enthalpyentropy compensation effect. It is shown that in general if the rate or equilibrium constant of a reaction does not change with changing conditions (such as solvent, substituents, etc.) then either the quantities of activation at constant pressure, ΔHp≠ and ΔSp≠, or the corresponding quantities at constant volume, ΔUv≠ and ΔSv≠, must vary in a compensating manner, and the existence of an energy–entropy compensation effect is inevitable. For the enolization of acetone and acetophenone in ethanol–water mixtures, ΔUv≠ and ΔSv≠ vary only slightly with solvent, whereas ΔHp≠ and ΔSp≠ vary in a compensating manner. The main causes of the compensation effect in the constant-pressure parameters are, in a sense, the change with changing solvent of the thermal expansion of the solvent and of the volume of activation of the reaction. On the other hand, both the constant-pressure and the constant-volume parameters vary with substituent from acetone to acetophenone, and the constant-volume parameters vary the more.

The secondary α-deuterium isotope effect at the site of the enzyme-catalyzed cis-trans isomerization of maleylacetone. Mechanistic implications

1999 ◽  
Vol 77 (5-6) ◽  
pp. 557-564
Author(s):  
Michael S Finnin ◽  
Stanley Seltzer
Keyword(s):  
Isotope Effect ◽  
Nucleophilic Addition ◽  
Single Bond ◽  
Glutathione System ◽  
Competitive Reaction ◽  
Deuterium Isotope Effect ◽  
Detailed Mechanism ◽  
H Nmr ◽  
Trans Isomerization ◽  
Isomerization Mechanism

An equal mixture of monodeuterated isotopomers of maleylacetone, viz., 4-hydroxy-6-oxo-2,4-heptadienoic-2-d1 acid (1) and 4-hydroxy-6-oxo-2,4-heptadienoic-3-d1 acid (2) was synthesized and subjected to catalyzed cis-trans isomerization by the maleylacetoacetate cis-trans isomerase-glutathione system. These studies were designed to probe the detailed mechanism of enzyme-catalyzed cis-trans isomerization about the C-2—C-3 bond of the substrate. In the competitive reaction, 2 accumulates with respect to 1 at high extent of reaction. 1H NMR analysis indicates that 1 reacts 15% faster than 2 in line with a nucleophilic addition mechanism at C-2 rather than a conjugate addition mechanism at C-2 and C-3, to convert the C-2—C-3 double bond to a single bond to allow facile internal rotation.Key words: enzyme-catalyzed cis-trans isomerization, secondary α-deuterium isotope effect, maleylacetoacetate cis-trans isomerase, cis-trans isomerization mechanism.

ChemInform Abstract: BETA-DEUTERIUM ISOTOPE EFFECT IN THE ACID CATALYZED RACEMIZATION OF TERT.-BUTYLPHENYLSULPHOXIDE

1974 ◽  
Vol 5 (28) ◽  
Author(s):  
PIERO BONVICINI ◽  
ARRIGO LEVI ◽  
GIANFRANCO SCORRANO
Keyword(s):  
Isotope Effect ◽  
Deuterium Isotope Effect ◽  
Acid Catalyzed

scholarly journals alpha-Hydroxylation of fatty acids in brain. Substrate specificity and deuterium isotope effect.

1977 ◽  
Vol 252 (15) ◽  
pp. 5206-5210
Author(s):  
S Murad ◽  
R H Chen ◽  
Y Kishimoto
Keyword(s):  
Fatty Acids ◽  
Substrate Specificity ◽  
Isotope Effect ◽  
Deuterium Isotope Effect

ChemInform Abstract: SOLVENT DEUTERIUM ISOTOPE EFFECT ON HYDROLYSIS OF BORIC ACID

1978 ◽  
Vol 9 (26) ◽  
Author(s):  
M. MAEDA ◽  
Y. SUNAOKA ◽  
H. KAKIHANA
Keyword(s):  
Boric Acid ◽  
Isotope Effect ◽  
Deuterium Isotope Effect ◽  
Hydrolysis Of

The Secondary β-Deuterium Isotope Effect and the Cage Effect in the Thermal Decomposition of Azobis-α-phenylethane1

1966 ◽  
Vol 88 (16) ◽  
pp. 3775-3781 ◽  
Author(s):  
Stanley Seltzer ◽  
Edwin J. Hamilton
Keyword(s):  
Thermal Decomposition ◽  
Isotope Effect ◽  
Cage Effect ◽  
Deuterium Isotope Effect

Partial kinetic ‘resolution’ resulting from a deuterium isotope effect

1991 ◽  
Vol 0 (12) ◽  
pp. 801-802 ◽  
Author(s):  
Panayiotis Anastasis ◽  
Raymond Duffin ◽  
Christopher Gilmore ◽  
Karl Overton
Keyword(s):  
Isotope Effect ◽  
Kinetic Resolution ◽  
Deuterium Isotope Effect

ChemInform Abstract: EXCESS ENTHALPY OF (TETRACHLOROMETHANE + 2-PROPANONE): DEUTERIUM ISOTOPE EFFECT

1985 ◽  
Vol 16 (17) ◽  
Author(s):  
E. KENYON-BLAIR ◽  
K. W. MORCOM
Keyword(s):  
Isotope Effect ◽  
Excess Enthalpy ◽  
Deuterium Isotope Effect
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