Concentrated sulfuric acid reacts with alkenes, alcohols and sodium halides - AQA - A-Level Chemistry - Question 2 - 2017 - Paper 3

1. The concentrated sulfuric acid acts as an electrophile and donates a proton (H⁺) to the alkene (propene). This forms a carbocation intermediate.

2. The most stable carbocation will form, which is the secondary carbocation.

3. The bisulfate ion (HSO₄⁻) then attacks the carbocation, resulting in the formation of the major product, isopropyl hydrogen sulfate.

4. Finally, upon hydrolysis, the product converts to isopropanol.

The minor product, which is formed under specific conditions, is likely to be propyl hydrogen sulfate or a less stable alkyl sulfate.

The major product is favored due to the stability of the secondary carbocation formed during the reaction. Secondary carbocations are more stable than primary carbocations due to hyperconjugation and inductive effects, which explains the preferential formation of the isopropyl hydrogen sulfate.

1. But-2-ene:

2. Isobutylene (2-methylpropene):

3. But-1-ene:

1. But-2-ene
2. 2-Methylpropene (Isobutylene)
3. But-1-ene

The by-product is butan-2-ol. The role of sulfuric acid is to protonate the alcohol, facilitating the elimination reaction leading to alkene formation. A suitable method for separation could be distillation.

The observation would include the formation of a white precipitate of sodium bisulfate.

The role of sulfuric acid in this reaction is to act as a dehydrating agent, promoting the reaction between sodium chloride and the release of hydrogen chloride.

The black solid observed is likely iodine.

The yellow solid is likely sulfur.

The gas produced with the smell of bad eggs is hydrogen sulfide (H₂S).