Statement I: In the human body, methanol is oxidised first to methanal and then to methanoic acid, which may cause blindness.
Statement II: A methanol-poisoned patient is treated by giving intravenous infusions of diluted ethanol.
In the light of the above statements, choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Both Statement I and Statement II are correct.
In the body, alcohols undergo biological oxidation: an alcohol is oxidised to the corresponding aldehyde and then to the acid. For methanol these products are poisonous.
Statement I: In the human body, methanol is oxidised first to methanal and then to methanoic acid, which may cause blindness. — True. The oxidation goes through the aldehyde to the acid, and the methanoic acid formed may cause blindness and even death:
\( \displaystyle \ce{CH3OH -> HCHO -> HCOOH} \)
Statement II: A methanol-poisoned patient is treated by giving intravenous infusions of diluted ethanol. — True. The ethanol swamps the enzyme that oxidises methanal (HCHO) to the acid. This allows time for the kidneys to excrete the methanol.
NCERT (2026-27 edition):
7.4.4 Chemical Reactions – “Biological oxidation of methanol and ethanol in the body produces the corresponding aldehyde followed by the acid.” … “In the body, methanol is oxidised first to methanal and then to methanoic acid, which may cause blindness and death. A methanol poisoned patient is treated by giving intravenous infusions of diluted ethanol. The enzyme responsible for oxidation of aldehyde (HCHO) to acid is swamped allowing time for kidneys to excrete methanol.”