Chemistry 9701 · AS & A Level · Hydrocarbons

Hydrocarbons — practice question

Tulobuterol is present in some medicines.
(a)[3]

Tulobuterol contains a benzene ring in its structure. Describe and explain the shape of benzene. In your answer, include: the bond angle between carbon atoms; the hybridisation of the carbon atoms; how orbital overlap forms $\sigma$ and $\pi$ bonds between the carbon atoms.

(b(i))[1]

Write an equation showing how $\text{Cl}_2$ reacts with $\text{AlCl}_3$ to produce an electrophile.

(b(ii))[3]

Complete the mechanism in Fig. 5.3 for the reaction between benzene and the electrophile formed in b(i). Include every relevant curly arrow and charge, and draw the intermediate structure.

(c(i))[1]

Name the mechanism for the reaction in step 2.

(c(ii))[1]

Draw an isomer of $Q$ that is formed as an organic by-product in step 2.

(c(iii))[3]

The reactants used in step 2 include acyl chloride, alkyl chloride and aryl chloride functional groups. State and explain how readily acyl chlorides, alkyl chlorides and aryl chlorides undergo hydrolysis.

(d)[3]

Suggest reagents and conditions for steps 3 and 4, and draw the structure of $Z$ in the box.

(e(i))[1]

Define enantiomers.

(e(ii))[1]

Suggest one disadvantage of making two enantiomers in this synthesis.

(e(iii))[1]

Suggest a method of adapting the synthesis to give a single enantiomer.

(f(i))[1]

Predict how many peaks would be seen in the carbon-13 NMR spectrum of tulobuterol.

(f(ii))[3]

The proton ($^1\text{H}$) NMR spectrum of tulobuterol dissolved in $\text{D}_2\text{O}$ shows peaks from four different proton environments. The peak for the $-\text{CH}_2-\text{N}-$ environment is a doublet in the chemical shift range $\delta = 2.0$-$3.0\,\text{ppm}$. Give details for each of the other three peaks in the proton NMR spectrum of tulobuterol, including the chemical shift, proton environment, splitting pattern, and number of $^1\text{H}$ atoms responsible.

Worked solution & mark scheme

This 22-mark question has a full step-by-step worked solution and mark scheme. One marking point: Any three aromaticity features, for example $120^\circ$ bond angles, a planar ring, $sp^2$ carbon, or delocalised $\pi$ electrons

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