Anàlisi predictiva de catalitzadors per generar hidrogen molecular

Abstract

The synthesis of oxalamides via acceptorless dehydrogenative coupling between

ethylene glycol and amines is a novel and improved method to obtain these versatile and

valuable compounds. The conventional methods used so far have low atomic economy

and generate waste or utilize toxic agents.

The aim of this final degree thesis is to computationally study the results described by

Milstein and collaborators with different amine substituents that, using a ruthenium

catalyst and tBuOK as base, react with ethylene glycol to form oxalamides in an

environmentally friendly manner. Additionally, it is a reaction where the hydrogenation of

the product with the same catalyst completes the retrieval of the initial amines and

ethylene glycol with high yield.

In this project, 26 species of amines were studied to determine which would be the most

viable for synthesis considering their geometric optimizations and those of the respective

amides. To carry out these computational calculations, the BP86 functional was used

with Def2-SVP bases for both the amines and the amides, with the temperature set at

135 ºC. Subsequently, a single-point energy calculation was performed in the presence

of the solvent toluene using the B3LYP functional and the Def2-TZVP basis set for the

atoms.

From the energies that we obtained, the Gibbs activation energy for each species of

amine and amide was calculated. Based on these results, the effects of each substituent

modification on this reaction were justified.

Additionally, complementary tests were conducted on the gas phases of the initial and

final species to obtain more information, specifically the energy of the HOMO and LUMO

orbitals and the nitrogen charge. Steric maps were also created to determine the degree

of occupation of the amine substituents that will affect the ruthenium catalyst in carrying

out the reaction.

The conclusion has been reached that the neither the thermodynamics, nor the kinetics

or any of the parameters studied, at the structural and/or electronic level allow finding

any correlation with the experimental yields