Master thesis

Synthesis and computational study of new geodesic polyarenes designed for molecular hydrogen storage and investigation of the Dakin-West reaction mechanism



Mémoire de master: Université de Fribourg, 2013

English This work presents the synthesis of a new geodesic polyarene molecule based on corannulene’s motive and especially designed for hydrogen storage. Indeed such curved systems are bearing a dipole moment which can polarize H2 molecules resulting in their adsorption. The complexation of our target molecules with alkali ions would increase their dipole moment as well as the interstitial volume between the molecular stacks thus increasing the hydrogen storage capabilities. In the first part, DFT calculations were undertaken to compare our target molecule with other curved systems and to point out the advantages or inconvenients for hydrogen storage applications. Two main synthetic pathways were postulated, the first one starting from 2,6-difluoroacetic acid and the other starting from 2,6-dichlorophenylacetic acid. In the first it was planned that the cyclized target molecule would be obtained by fluorhydric acid elimination which was a recently discovered means of curvature introduction; the second would result of flash vacuum pyrolysis or palladium catalyzed reaction which are already well known for such purposes. Unfortunately problems were encountered at the first step in each pathway, namely during the bisbenzyl ketone synthesis. The Dakin-West reaction was initially explored, but it proved to be inefficient and because its mechanism was not well understood, computational calculations supported by ESI-MS measurements were undertaken. Bisbenzyl anhydride was identified as intermediate, thus it was tested as a starting reagent treated with 4-dimethylaminopyridine but without success except when starting from unsubstituted 2-phenylacetic anhydride. For each pathway Claisen condensation was tested and offered the desired bisbenzyl ketone from the corresponding ester, but only in poor yields. A third approach in which 2-(2,6-dichlorophenyl)acetyl chloride was reacted with a Grignard reagent formed from 2-(bromomethyl)-1,3-dichlorobenzene and magnesium was tested. Unfortunately Wurtz coupling between brominated species was mainly observed thus hindering the production of bisbenzyl ketone as major product.
Faculté des sciences et de médecine
Département de Chimie
  • English
License undefined
  • RERO DOC 208667
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