Final answer:
The most acidic compound among the given choices is 1-hexyne because it is a terminal alkyne with a hydrogen that forms a more stabilized acetylide anion upon deprotonation.
Step-by-step explanation:
To determine which of the following is the most acidic compound, we need to look at the stability of the anion that would form upon deprotonation. The compounds to consider are: 1-hexene (a), 1-hexyne (b), 3-hexyne (c), and 2,5-dimethyl-3-hexyne (d).
Since acidic strength in hydrocarbons typically increases with the presence of electron-withdrawing groups and sp hybridized carbons (as in alkynes), the most acidic compound would be 1-hexyne or 3-hexyne. The terminal alkyne in 1-hexyne has a hydrogen that can be deprotonated to form an acetylide anion, which is stabilized through sp orbital interaction with the remaining carbon atom. The internal alkyne in 3-hexyne is less acidic because the cation that forms is less stable. Therefore, between the given options, 1-hexyne is the most acidic.
However, if we also consider 2,2-dimethyl-3-hexyne, this molecule contains two methyl groups at the second carbon which are electron-donating by induction, making the nearby acetylenic hydrogen less acidic compared to 1-hexyne.