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Calorimetrically measurable enthalpic isotope effect
Kent Ballard1, Richard C Reiter, Cheryl D Stevenson
1Department of Chemistry, Illinois State University, Normal, IL 61790-4160, USA.
The Journal of Physical Chemistry. A
|December 22, 2006
Summary
The reaction of perdeuterated naphthalene anion radicals with water is more exothermic than the perprotiated system. This suggests that perdeuteration decreases the heat of naphthalene hydrogenation.
Area of Science:
- Physical Chemistry
- Chemical Thermodynamics
- Isotope Effects
Background:
- Naphthalene and its anion radical are important in organic chemistry.
- Isotope effects on chemical reactions can provide insights into reaction mechanisms.
- Calorimetric studies are crucial for determining reaction enthalpies.
Purpose of the Study:
- To investigate the effect of deuterium substitution on the enthalpy of reaction of the naphthalene anion radical with water.
- To determine the impact of perdeuteration on the heat of hydrogenation of naphthalene.
Main Methods:
- Calorimetric measurements were used to determine the enthalpy of reaction.
- The study compared the reaction of perdeuterated naphthalene anion radical with water to the perprotiated system.
- Enthalpy of electron transfer between naphthalene and its perdeuterated analogue was considered.
Main Results:
- The reaction of the perdeuterated naphthalene anion radical with water was found to be more exothermic by approximately 2.2 kcal/mol compared to the perprotiated system.
- The heat of hydrogenation of naphthalene was calculated to decrease by about 1.8 kcal/mol upon perdeuteration.
Conclusions:
- Perdeuteration of naphthalene leads to a more exothermic reaction with water for its anion radical.
- The observed isotope effect indicates a significant influence of deuterium on the thermodynamics of naphthalene hydrogenation.
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