Question

An organic compound with molecular formula C7H8O dissolves in NaOH and gives a characteristic colour with FeCl3. On treatment with bromine, it gives a tribromo derivative C7H5OBr3. The compound is

• A. m - Cresol
• B. Benzyl alcohol
• C. p - Cresol
• D. o - Cresol

Answer 1

Answer: (A)

m - Cresol

Answer 2

Cresols are aromatic compounds with the general formula $\text{C}_6\text{H}_4(\text{CH}_3)(\text{OH})$
They are derivatives of phenol, where the methyl group $(CH_3)$ is substituted on the benzene ring.
Cresols have three isomers:

• o-cresol (ortho-cresol),
• m-cresol (meta-cresol), and
• p-cresol (para-cresol).

When m-cresol $(\text{C}_7\text{H}_8\text{O})$ is treated with bromine $(Br_2)$, it undergoes electrophilic aromatic substitution and forms a tribromo derivative, $\text{C}_7\text{H}_5\text{OBr}_3$
In this case, the compound is brominated at the meta position on the benzene ring, resulting in tribromination.
The given molecular formula $\text{C}_7\text{H}_8\text{O}$ corresponds to the molecular formula of m-cresol. Furthermore, m-cresol is known to dissolve in NaOH and gives a characteristic color with $FeCl_3.$
Therefore, the organic compound in question is m-cresol (option A).