An excess consumption of which of these compounds causes blindness and death?

Methanol

The correct answer is option 1. Methanol.

Methanol, also known as wood alcohol, is a simple alcohol compound. When ingested, it is metabolized in the liver by the enzyme alcohol dehydrogenase to formaldehyde, a highly toxic substance.

Optic Nerve Damage: One of the most significant and well-known effects of methanol poisoning is damage to the optic nerve, leading to vision impairment and even blindness. Formic acid is believed to be responsible for this optic nerve damage.

Fatality: In severe cases of methanol poisoning, if left untreated, it can lead to coma, seizures, respiratory failure, and ultimately death.

In contrast, ethanol (option 2), methanal (option 3, also known as formaldehyde), and methanoic acid (option 4, also known as formic acid) are not as toxic as methanol when ingested in moderate amounts. Ethanol is the type of alcohol found in alcoholic beverages and is metabolized differently from methanol. Methanal and methanoic acid are metabolites of methanol but are not as potent toxins as methanol itself.

Therefore, an excess consumption of methanol (option 1) is the most likely to cause blindness and death due to its toxic metabolites, particularly formic acid, and its damaging effects on the optic nerve and vital organs.