Sintese van amino-arielaldehied verbindings

MSc (Chemistry), North-West University, Potchefstroom Campus, 2015

Die soeke na sterk hoë-verrigtingspolimere het gelei tot die idee om ʼn volledig gekonjugeerde polimeer te ontwikkel vir moontlike gebruik in die motorindustrie. Hierdie polimeer moet soortgelyke eienskappe as dié van Kevlar besit, aangesien die beoogde polimeer vir die bakwerk van battery-aangedrewe voertuie gebruik sou kon word. Die selfpolimerisasie van 4,6-diaminobenseen-1,3-dikarbaldehied is as die gewenste gekonjugeerde polimeer beskou. Tydens die studie is daar gefokus op die sintese van die monomeer 4,6-diaminobenseen- 1,3-dikarbaldehied. Die sintese van monomere wat beide funksionele groepe wat aan die polimerisasie deelneem, op dieselfde molekuul besit, was uitdagend, omdat hierdie monomere baie maklik selfpolimerisasie kan ondergaan. Hierdie studie het ook na groener en korter sinteseroetes om 4,6-diaminobenseen-1,3-dikarbaldehied of derivate daarvan te sintetiseer gekyk, aangesien die sintese van 4,6-diaminobenseen-1,3-dikarbaldehied in die verlede met baie lang sinteseroetes en gevaarlike chemikalieë uitgevoer is. Sintese van 1,5-dibromo-2,4-dimetielbenseen (1), 1,5-dibromo-2,4-bis(dibromometiel)- benseen (2), 4,6-dibromobenseen-1,3-dikarbaldehied (3) en 1,3-bis([1,3]dioksolaan)-4,6- dibromobenseen (5) is suksesvol uitgevoer, maar tydens die koper-gekataliseerde Ullmanntipe reaksies om 4,6-diaminobenseen-1,3-dikarbaldehied (4) te sintetiseer, het slegs poeiers gevorm wat nie oplosbaar in organiese oplosmiddels is nie. Om die selfpolimerisasie moontlikhede van 4 uit te skakel is 5 gesintetiseer. ʼn Poging om 1,3-bis([1,3]dioksolaan)- 4,6-diaminobenseen (6a) vanaf 5 te sintetiseer het egter tot geen reaksie gelei nie. Molekuulmodellering van die Ullmann-tipe reaksies om 6a en 4,6-dimetielbenseen-1,3- diamien te sintetiseer is gedoen om die reaksie te ondersoek. Daar is gevind dat ʼn 1,3- diketoonligand wat aan die koperkatalisator bind, nodig is om die reaksie te verbeter. Vanuit die resultate van die studie is ook gevind dat ʼn Ullmann-tipe reaksie nie met 5 sal plaasvind nie, aangesien dit energeties nie so voordelig is nie. Spektroskopiese analise van die poeiers wat tydens die sintese van 4 gevorm het, bevestig dat die poeiers polimere is. Dit blyk egter dat dit nie die voorgestelde rigiede polimeer is wat gevorm het nie, maar dat dit eerder ʼn amorfe kinasolientipe produk is.

The quest for strong high performance polymers led to the idea of the development of a fully conjugated polymer for possible use in the automotive industry. These polymers have similar characteristics to those of Kevlar, since the new polymer is intended for the body of battery-powered vehicles. The self-polymerisation of 4,6-diaminoisophthalaldehyde is intended as the desired conjugated polymer. The study focused on the synthesis of the monomer, 4,6-diaminoisophthalaldehyde. The synthesis of monomers containing both functional groups reacting during polymerisation on the same molecule is challenging because these monomers easily undergo selfpolymerisation. This study also investigated shorter and greener synthesis routes to synthesise 4,6-diaminoisophthalaldehyde or derivatives thereof as the synthesis of 4,6- diaminoisophthalaldehyde used long synthesis routes and dangerous chemicals in the past. Synthesis of 1,5-dibromo-2,4-dimethylbenzene (1), 1,5-dibromo-2,4-bis(dibromomethyl)-benzene (2), 4,6-dibromoisophthalaldehyde (3) and 1,3-bis([1,3]dioxolane)-4,6-dibromobenzene (5) have been successfully carried out. During the copper-catalysed Ullmann-type reactions to synthesise 4,6-diaminoisophthalaldehyde (4) only powders formed that do not dissolve in solvents. In order to prevent the self-polymerization of 4, 5 was synthesised. Synthesis of 1,3-bis([1,3] dioxolane)-4,6-diaminobenzene (6a) from 5 yielded no results. Molecular modelling of the Ullmann-type reactions to synthesise 6a and 4,6-dimethylbenzene-1,3-diamine was done to investigate the reaction. It was found that a 1,3-diketone ligand bonded to the copper catalyst is needed to improve the reaction. From the results of the study it was also found that an Ullmann-type reaction with 5 will not occur because it is energetically unfavourable. Spectroscopic analysis of the powders formed during the synthesis of 4, confirmed that the powders are polymers. However, it seems that it is not the proposed rigid polymer that is formed, but rather an amorphous quinazoline-type product.

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