Theoretical study of decomposition mechanism of Pyruvic Acid
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Theoretical study of decomposition mechanism of Pyruvic AcidAutoria
Tutor/Supervisor
Oliva Domínguez, MónicaTutor/Supervisor; Universitat.Departament
Universitat Jaume I. Departament de Química Física i AnalíticaData de publicació
2016-07-28Editor
Universitat Jaume IResum
In this work, the decomposition reaction of pyruvic acid has been studied,
some mechanisms are based on the proposal that Gabriel da Silva presents in
its theoretical study of this decomposition process.
The study ... [+]
In this work, the decomposition reaction of pyruvic acid has been studied,
some mechanisms are based on the proposal that Gabriel da Silva presents in
its theoretical study of this decomposition process.
The study has been made from two viewpoints. The first one is an energetic
and geometric analysis of the stationary points involved in the different pathways.
The second one consists in a topological study of some mechanisms.
The mechanisms proposed by Gabriel da Silva have been reproduced and
similar geometric and energetic results have been found.
The mechanism-A is the most favorable kinetically because the reactants
have to pass through less energetic energy barriers to reach the products, in this
case acetic acid and carbon monoxide. On the other hand, the mechanism-D is
the most favorable thermodynamically because obtaining acetaldehyde has the
most negative reaction free energy (-12.48 Kcal/mol). However, mechanism D
has a high energy barrier (73.2 Kcal/mol).
Furthermore, two alternatives to mechanism A (mechanisms A’ and A’’) have
been characterized. All three mechanisms give acetic acid and carbon monoxide
as products. These new alternatives have been calculated at the same theoretical
level as the previous proposed mechanism and the energetic and geometric
study has been extended with a topological analysis.
Gibbs free energies of the mechanism A are similar to the mechanism A’,
there is only a small difference of 2.21 kcal/mol in the first transition state,
nevertheless, the energies of the other stationary points are the same in both
mechanisms. These are stepwise mechanisms where the first transition state is
associated to a hydrogen transfer between the alcohol and carbonyl groups and
to a C-O bond formation that closes the epoxide ring. The difference between
both mechanisms is the oxygen that forms the epoxide group, so both
intermediates are enantiomers. In the second TS, the C-C and the other C-O
bond of the epoxide ring are broken giving acetic acid and carbon monoxide. The
geometric analysis reveals than in the first TS the hydrogen transfer in much more
advanced than the C-O bond formation. In the same way, in the second TS the
C-O bond distance is longer than the C-C one.
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The description that emerges from the topological [-]
Paraules clau / Matèries
Descripció
Treball Final de Grau en Química. Codi: QU0943. Curs: 2015/2016
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info:eu-repo/semantics/bachelorThesisDrets d'accés
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Apareix a les col.leccions
- Grau en Química [265]