Chemistry 9701 · AS & A Level · Analytical techniques

Analytical techniques — practice question

(a)[2]

Define what is meant by the term partition coefficient, $K_{pc}$.

(b(i))[2]

For benzoic acid, $K_{pc}$ between octan-1-ol and water is $79.4$.\n\nA $0.400\,\text{g}$ portion of benzoic acid in $25.0\,\text{cm}^3$ octan-1-ol is shaken with $125\,\text{cm}^3$ of water. Calculate the mass of benzoic acid taken into the water layer.

(b(ii))[1]

The $K_{pc}$ of benzophenone, $\text{C}_6\text{H}_5\text{COC}_6\text{H}_5$, between octan-1-ol and water is not the same as the $K_{pc}$ of benzoic acid in (b)(i). Explain why.

(c(i))[2]

Benzophenone may also be prepared in two steps from benzoic acid as shown. In step 1, compound J, a reactive intermediate, is formed. Compound J then reacts with an organic compound, K, to make benzophenone.\n\nDeduce the identities of organic compounds J and K and draw their structures in the boxes.

(c(ii))[1]

Suggest suitable reagents and conditions for step 1.

(d(i))[1]

Benzophenone can also be made in two steps from bromomethylbenzene.\n\nDeduce the identity of compound L and draw its structure in the box.

(d(ii))[2]

Name the mechanism of step 3 and suggest reagents and conditions for step 3.\n\nmechanism of step 3 ...............\n\nreagents and conditions ...............

(d(iii))[1]

Deduce the reaction type in step 4.

(e(i))[1]

Deduce how many peaks would appear in the carbon-13 NMR spectrum of benzophenone.

(e(ii))[2]

Identify two different carbon environments that would cause different chemical shift ranges in the carbon-13 NMR spectrum of benzophenone.

Worked solution & mark scheme

This 15-mark question has a full step-by-step worked solution and mark scheme. One marking point: the concentration ratio of a solute in two immiscible solvents

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