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

1. The concentrated sulfuric acid donates a proton (H⁺) to the double bond in propene, forming a carbocation intermediate.
2. The hydrogen from H₂SO₄ attaches to one of the carbon atoms in the double bond, leading to the more stable carbocation being formed.
3. The bisulfate ion (HSO₄⁻) then attacks the carbocation, leading to the formation of the major product, isopropyl hydrogen sulfate.

The structure of the minor product is drawn as follows:

 CH3
  |  

CH3- C - OH |
O- H

The product is the major product due to the stability of the carbocation formed during the reaction. The more stable secondary carbocation leads to preferential formation of the isopropyl hydrogen sulfate over any potential minor products.

1. CH3-CH=CH-CH3 (2-butene)
2. CH3-CH(CH3)-CH=CH2 (2-methylpropene)
3. CH2=CH-CH2-CH3 (1-butene)

Names:

1. But-2-ene
2. 2-Methylpropene
3. But-1-ene

By-product: Butanol (C4H10O)

Role of sulfuric acid: It acts as a dehydrating agent, facilitating the elimination reaction to form the alkenes while producing the by-product.

Name of separation method: Distillation could be used to separate the products.

Observation: The reaction between concentrated sulfuric acid and solid sodium chloride would produce sodium hydrogen sulfate and hydrogen chloride gas, which is visible as white fumes.

Role of sulfuric acid: It acts as a catalyst in the reaction, helping to produce hydrogen chloride from sodium chloride.

Observation: The black solid is typically iodine formed during the reaction with iodide.

Observation: The yellow solid produced is likely iodine monochloride.

Observation: The gas produced, which smells like bad eggs, is hydrogen sulfide (H₂S).