Q51E - Organic Chemistry (Mcmurry)

Question

Predict the major product (s) you would obtain from sulfonation of the following compounds:

1. Fluorobenzene
2. m-Bromophenol
3. m-Dichlorobenzene
4. 2,4-Dibromophenol

Step-by-Step Solution

Answer

1. p-fluorobenzene-sulfonic acid and o-Fluorobenzenesulfonic acid Phenol.
2. 2-Bromo-4-Hydroxy-benzenesulfonic acid and 4-Bromo-2 hydroxybenzenesulfonic acid.
3. 2,4-Dichlorobenzene-sulfonic acid.
4. 3,5-Dibromo-2-hydroxy-benzenesulfonic acid.

Step-by-Step Solution Step 1: Sulfonation

Sulfonation is a reaction where a sulfonic acid functional group is introduced into the molecule.

If the sulfonic acid group is introduced in aromatic compounds, then it is aromatic Sulfonation. For example- The method of heating benzene with fuming sulphuric acid to form benzenesulfonic acid is known as sulfonation of benzene.

Step 2: Sulfonation of Fluorobenzene

Sulfonation of fluorobenzene gives p-fluorobenzene-sulfonic acid and o-Fluorobenzenesulfonic acid as fluorine increases the electron density at the ring through mesomeric effect and is ortho and para directing group.

Sulfonation of Fluorobenzene

Step 3: Sulfonation of m-bromophenol

Sulfonation of m-bromophenol

Both, -OH and –Br are ortho and para directing and since, substitution between two groups rarely occurs, so the two products formed are 2-Bromo-4-Hydroxy-benzenesulfonic acid and 4-Bromo-2-hydroxybenzenesulfonic acid.

Step 4: Sulfonation of m-dichlorobenzene

Sulfonation of m-dichlorobenzene gives   2,4-Dichlorobenzene-sulfonic acid as –Cl is ortho and para directing group.

Sulfonation of m-dichlorobenzene

Step 5: Sulfonation of 2,4-Dibromophenol

Sulfonation of 2,4-Dibromophenol

The product formed as a result of sulfonation of 2,4-Dibromophenol is 3,5-Dibromo-2-hydroxy-benzenesulfonic acid.