The IUPAC name of methyl acetylene is:

1. Propyne
2. Ethene
3. Propane
4. Ethyne

Propyne

Reason — Methyl acetylene is a common name for a compound that has three carbon atoms and a triple bond between two of them.

• The compound has 3 carbon atoms, so the root name is "prop-".
• It contains a triple bond, which is indicated by the suffix "-yne".
• So the IUPAC name becomes Propyne.

Let's analyze the given options:

1. Propyne — Correct IUPAC name of methyl acetylene.
2. Ethene — Has 2 carbon atoms and a double bond → Incorrect.
3. Propane — Has 3 carbon atoms but only single bonds → Incorrect.
4. Ethyne — Has 2 carbon atoms and a triple bond → Incorrect.