Chemistry 9701 · AS & A Level · Halogen compounds

Halogen compounds — practice question

Although halogenoalkanes are seldom found in nature, they are significant as intermediates in organic reactions and as solvents. The bromoalkane B has the following mass composition: C, 29.3%; H, 5.7%; Br, 65.0%. The relative molecular mass of B is 123.
(a)[3]

Calculate the molecular formula for B.

(b(i))[4]

When hot aqueous $\text{NaOH}$ is used, $\text{C}_2\text{H}_5\text{Br}$ is hydrolysed to ethanol, $\text{C}_2\text{H}_5\text{OH}$. Describe the mechanism for this reaction. Your answer should include any relevant charges, dipoles, lone pairs of electrons and the movement of electron pairs shown with curly arrows.

(b(ii))[1]

What is produced when $\text{C}_2\text{H}_5\text{Br}$ is reacted with $\text{NaOH}$ under different conditions?

(b(iii))[1]

Which condition is used?

(b(iv))[1]

What type of reaction is shown here?

(c(i))[1]

Draw the displayed formula of the product formed when 1,4-dichlorobutane, $\text{ClCH}_2\text{CH}_2\text{CH}_2\text{CH}_2\text{Cl}$, is reacted with hot aqueous $\text{NaOH}$ as in (b)(i).

(c(ii))[1]

Draw the skeletal formula of the product formed when 1,4-dichlorobutane is reacted with $\text{NaOH}$ in the manner described in (b)(ii) and (b)(iii).

Worked solution & mark scheme

This 12-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Empirical atom ratio $\text{C} : \text{H} : \text{Br} = 3 : 7 : 1$” …

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