Chemistry 9701 · AS & A Level · Organic synthesis

Organic synthesis — practice question

The preparation of 4-nitromethylbenzene can be carried out by the electrophilic substitution reaction shown.
(a(i))[1]

As a side-product, this reaction also produces an isomer of 4-nitromethylbenzene. Draw the structure of that side-product.

(a(ii))[1]

Write an equation for the reaction of $\text{HNO}_3$ with $\text{H}_2\text{SO}_4$ that generates the electrophile for this reaction.

(a(iii))[3]

Describe the ways in which the structure and bonding of the six-membered ring in intermediate T are different from those in methylbenzene.

(b(i))[1]

Give the systematic name for compound W.

(b(ii))[6]

Suggest the reagents and conditions needed for steps 1-5.

(c)[2]

Suggest how the basicity of benzocaine compares with that of ethylamine. Explain your answer.

(d(i))[1]

Predict how many peaks would appear in the carbon-13 NMR spectrum.

(d(ii))[1]

Benzocaine was dissolved in $\text{CDCl}_3$, and the proton NMR spectrum of the solution was recorded. Suggest why $\text{CDCl}_3$ is chosen instead of $\text{CHCl}_3$ as the solvent for recording a proton NMR spectrum.

(d(iii))[4]

Use the Data Booklet together with the spectrum in (d)(ii) to complete the table for the proton NMR spectrum of benzocaine. The actual chemical shifts, $\delta$, for the four absorptions are shown.

(d(iv))[1]

Explain why the absorption at $\delta 1.2\,\text{ppm}$ has that splitting pattern.

(d(v))[1]

The proton NMR spectrum of benzocaine dissolved in $\mathrm{D_2O}$ was recorded. Suggest how this spectrum would be different from the spectrum in (d)(ii). Explain your answer.

(e(i))[1]

Suggest the reagents for step 1.

(e(ii))[2]

Suggest the structures of compounds R and S and draw them in the boxes.

Worked solution & mark scheme

This 25-mark question has a full step-by-step worked solution and mark scheme. One marking point: Nitrotoluene structure drawn correctly

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