ESTUDO DA CINÉTICA DA REAÇÃO QUÍMICA TRADICIONAL E ELETROQUÍMICA DE TETRABROMAÇÃO DO P-XILENO E DO 2,5-DICIANO-PXILENO

Abstract

The text of this paper is divided into three chapters. In Chapter 1 there is a bibliographic review where the application of brominated organic compounds is presented, the main form of synthesis of these and the changes that have been occurring due to the use of solvents harmful to the ozone layer. It will be described alternative methods of synthesis, and the most approached is the electrochemical method used, therefore in this work, through which it is possible to perform the bromination of aromatic rings and bromination of aromatics in the benzylic position. The applications of the synthesized compounds: α, α, α', α'-tetrabromo-p-xylene and α, α, α ', α'-tetrabromo-2,5-dicyano-p-xylene will also be presented. In Chapter 2 we present experimental and theoretical studies, where an explanation was sought for the differences observed in the traditional chemical reaction of benzylic tetrabromination in 2,5-dicyano-p-xylene compared to p-xylene. In order to do this, the reactions of Wohl-Ziegler were carried out for 10 hours. Samples were collected at each determined time. These samples were analyzed by Hydrogen Nuclear Magnetic Resonance (H1 NMR) and Gas Chromatography Coupled to Mass Spectrometry (CG-MS). A theoretical load study was also carried out from a computer simulation. What is observed is that the compound containing the nitrile substituent has a slower bromination reaction with the formation of four intermediate compounds, whereas for the compound without substituent the reaction is faster and only two intermediate compounds are observed. In Chapter 3 an alternative method of synthesis for the benzylic tetra-bromination of 2,5-dicyano-p-xylene and p-xylene is described. The production of these compounds occurs using electrochemical reactions, where it is not necessary to use solvents of prohibited sale (CCl4). Also, a kinetic monitoring was performed, analyzing the samples collected by H1 NMR and CG-MS, to make the comparison of synthesis by the traditional and electrochemical method. As the main difference observed is that in the electrochemical method the reactions are slower, also with this method it is possible to continue adding bromines in the benzylic position to the compound p-xylene, obtaining this compound pentabromado and hexabromado.