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Narrative
An aqueous solution of aniline is added to each of two Petri dishes containing a yellow aqueous solution of iodine and potassium triiodide. One dish also contains the anionic detergent sodium lauryl sulfate. The rate of iodination of aniline is shown by the disappearance of the yellow color.

Discussion
The electrophilic aromatic substitution reaction proceeds through positively charged intermediates which are stabilized by anionic detergents such as sodium lauryl sulfate with a subsequent enhancement in rate. The amine group is an ortho-para director. The mechanism for the formation of the ortho isomer is shown.