Friedel-Crafts Reaction Lab Essay

1363 Words Mar 24th, 2011 6 Pages
Experiment 10A Post-Lab
Feb. 10, 2010
Lab: CHEM2212
W 3:30-6:30

Title: The Friedel-Crafts Alkylation Reaction Synthesis of 1,4-di-t-butyl-2,5-dimethoxybenzene with 1,4-dimethoxybenzene and t-butyl alcohol and sulfuric acid

Introduction:

A Friedel-Crafts reaction is a type of electrophilic aromatic substitution reaction that consists of the introduction of an alkyl group onto the benzene ring, otherwise known as alkylation. The first step of Friedel-Crafts alkylation requires the generation of an intermediate carbocation to act as the electrophile during the aromatic substitution process. This is typically done through a reaction of an alkyl halide with a Lewis acid, but this can also be done by the addition of\ H+ to the
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A common characteristic of all activating groups is that they donate electrons to the ring, which in turn makes the ring more electron-rich, stabilizing the carbocation intermediate, and lowering the activation energy for its formation. In order to generate the electrophilic carbocation, t-butyl alcohol was treated with concentrated sulfuric acid. During this experiment, two equivalents of t-butyl alcohol were actually used to encourage disubstitution. The t-butyl groups substituted on the aromatic ring of 1,4-dimethoxybenzene. The first t-butyl group attached to the number two carbon of the ring, and then the second t-butyl group substituted at the position farthest from the first group (number five carbon) for steric reasons.

Conclusion:
In this experiment, 1,4-dimethoxybenzne reacted with two equivalents of t-butyl alcohol to form 1,4-di-t-butyl-2,5-dimethoxybenzene via a Friedel-Crafts alkylation mechanism. The electrophilic intermediate carbocation for the reaction was formed through the treatment of t-butyl alcohol with concentrated sulfuric acid. The percent yield was 31.07%, which is fairly low. This was lower due to the fact that many of the crystals remained stuck in the Pasteur pipet during removal of the solvents, and there may have possibly been crystals lost when removing them from the funnel for weighing, etc. There were multiple opportunities when crystals may have been lost.

The

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