What is the correct IUPAC name of the alkyne with the condensed structural formula H3C–C≡C–H?

Introduction / Context:
This organic chemistry question tests your ability to apply IUPAC nomenclature rules to a simple alkyne. The given condensed structural formula H3C–C≡C–H represents a linear chain of carbon atoms with a triple bond. Correctly counting the carbon atoms and numbering the chain allows you to select the correct IUPAC name.

Given Data / Assumptions:

• The condensed formula is H3C–C≡C–H.
• We assume a straight chain with no branching.
• We must name the compound according to IUPAC rules for alkynes.
• Options include acetylene, propyne, propene, butan-1-ol and decanoic acid.

Concept / Approach:
Alkynes are hydrocarbons that contain at least one carbon carbon triple bond and are named by replacing the suffix “ane” with “yne” in the corresponding alkane name. First, count the total number of carbon atoms in the longest chain containing the triple bond. Then, number the chain from the end nearer to the triple bond to assign the lowest possible number to the triple bond position. For a three carbon chain with a triple bond starting at carbon 1, the IUPAC name is prop-1-yne, commonly shortened to propyne.

Step-by-Step Solution:
1) Examine the formula H3C–C≡C–H and count the carbon atoms: CH3 (one carbon), then the central C in the triple bond and the terminal C≡C–H carbon, giving a total of 3 carbon atoms.2) Since there are three carbon atoms in a straight chain, the parent alkane name is propane.3) The presence of a carbon carbon triple bond means we replace “ane” with “yne,” so the base name becomes propyne.4) Number the carbon chain from the end nearer to the triple bond. If we start from the terminal –C≡C–H end, the triple bond starts at carbon 1.5) The detailed IUPAC name is therefore prop-1-yne, which can be written simply as propyne.6) Among the options, the correct IUPAC based choice is “Propyne (prop-1-yne).”

Verification / Alternative check:
Acetylene, also called ethyne, has the formula HC≡CH and contains only two carbon atoms. The given compound clearly has three carbons, so acetylene cannot be correct. Propene (prop-1-ene) has a double bond, not a triple bond. Butan-1-ol has four carbons and a hydroxyl group, and decanoic acid is a ten carbon carboxylic acid. None of these match the three carbon, triple bonded structure. Only propyne satisfies both the carbon count and the triple bond requirement, confirming that it is the correct IUPAC name.

Why Other Options Are Wrong:
Acetylene (ethyne): Contains two carbons and a triple bond (C2H2), not three carbons.
Propene (prop-1-ene): Has three carbons but contains a double bond, not a triple bond.
Butan-1-ol: Has a four carbon chain and an –OH group, so the functional group and carbon count do not match.
Decanoic acid: A ten carbon carboxylic acid, completely different from a simple three carbon alkyne.

Common Pitfalls:
Some students see the triple bond and think of acetylene, but forget to count the carbon atoms. It is essential to count the carbon chain length before naming any hydrocarbon. Others may overlook the difference between a double bond (alkene) and triple bond (alkyne) and choose propene by mistake. Always identify the functional group (single, double or triple bond) and then apply the appropriate suffix and numbering for the chain.

Final Answer:
The correct IUPAC name of H3C–C≡C–H is propyne (prop-1-yne).