Organic Chemistry Question: Consider the nucleophilic displacement of chloride i

Question

Organic Chemistry Question:

Consider the nucleophilic displacement of chloride in an aryl sulfonyl chloride by an aniline nitrogen (methanol solvent). Either ring may have substituents. The second aniline molecule in the equation simply serves as a base.

                 ArSO2Cl + 2H2NAr’ -> ArSO2NHAr’ + H3N(+)Ar’Cl(-)

A Bronsted plot may be constructed by varying the substituent on Ar’ (with Ar
constant) and plotting log k vs. pKa (for the conjugate acid of the amine). If such
a plot is made for each member of the Ar series, different values of are
obtained. For example, for p-NO2 in Ar, is 0.93; for p-OCH3, is 0.65. What
is the significance of this variation?

Explanation / Answer

The Bronsted plot gives the relationship between acid strenght and the acid catalysis. The gibbs free-energy is for the proton dissociation is proportional to the activation energy.

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