SolutionsElectrophilic Addition

Theory
Problems and exercises
Solutions
Where I am
Molecular panel (opens in a new tab)

1. Reactions of 1-pentyne

Predict the result of the following processes:

1-Pentyne with: H₂SO₄, H₂O, HgSO₄; 9-BBN then H₂O₂, NaOH; HBr (2 eq); HCl (1 eq); Br₂ (2 eq) in CCl₄; NaNH₂, NH₃ then MeI

Products: 2-pentanone, pentanal, 2,2-dibromopentane, 2-chloro-1-pentene, 1,1,2,2-tetrabromopentane and 2-hexyne

Acid hydration and HX addition follow Markovnikov's rule; hydroboration is anti-Markovnikov. With 2 equivalents of reagent the alkyne adds two molecules.

2. From alkyne to ketone

Which alkyne would you use to obtain 2-pentanone as the only hydration product? Why does 2-pentyne not work?

1-Pentyne. 2-Pentyne has two carbons with similar substituents and would give a mixture of 2-pentanone and 3-pentanone.

← Back to the exercises