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Unformatted text preview: Mapua I nstitute of Technology Organic Chemistry Laboratory 2 Final Report Factors Affecting the Relative Rates of Electrophilic Aromatic Substitution Reactions Von Joby M. Romero, K ristine S. Salvador School of Chemical Engineering and Chemistry, Mapua Institute of Technology, Intramuros, Manila, Philippines Experiment No. 1, Submitted on October 26, 2010 at N402 ABSTRACT This experiment centers the discourse on the electrophilic aromatic substitution reactions particularly, the factors which affects the rates for such reactions. On the first part, reaction of benzene, chlorobenzene, aspirin, acetanilide, p-nitrophenol, anisole, phenol with the reagent bromine were observed. It suggests that the compounds which reacts faster than benzene do probably have an activator substituents, and those that are slower has substituents that are deactivator. On the other hand, the effect of solvent, which are acetic acid and cyclohexane) on the bromination of anisole was also obtained. The reaction favors the reaction in the presence of more polar solvent. Lastly, the rates of reaction of acetanilide in ethyl acetate is determined based on varied temperature. By graphing, it can be easily observed that as temperature increases, reactivity increases. Keywords: electrophilic substitution, substituent effects, temperature effects, solvent effects, bromination of aromatic compounds 1 I N TRODUCT ION Aromatic compounds are compounds that contain a benzene ring – six-membered ring with alternating double and single bonds. These aromatic compounds although have multiple double bonds do not undergo addition reactions like alkenes. This weak reactivity of the compound towards addition reaction is due to stability of the ring systems which results from complete electron delocalization or resonance. π However, these compounds undergo electrophilic aromatic substitution reactions, in which aromaticity of the ring is preserved. I t is proven that benzene, which is a perfect example of aromatic compound, is unreactive due to stability. This stability is primary caused by the multiple resonance or complete π electron delocalization. Unlike alkenes which undergo addition reaction, aromatic compounds which also has multiple bonds rather reacts under electrophilic substitution. Such reactions are halogenation, nitration, sulfonation, alkylation and acylation. For that substitution, the reaction consists of an electrophile (E + ) and an electon rich aromatic ring (nucleophile). That electrophile would then be substituted to one of the H + which is attached to the benzene ring. For this experiment, we will focus the reaction of aromatic compound with bromine. In the mechanism, the determining rate of formation of electrophilic bromine is to be obtainef first. One of the double bond of the aromatic ring will attack the electrophilic bromine. The carbocation containing a bromine substituent will form. In order to be stable again, the hydrogen sharing the carbon bond with bromine will...
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