Chemistry 9701 · AS & A Level · States of matter

States of matter — practice question

(a)[4]

Compare the relative acidities of butanoic acid, ethanol, ethanoic acid and water, and explain your answer. $\ldots\ldots\ldots\ldots\ldots > \ldots\ldots\ldots\ldots\ldots > \ldots\ldots\ldots\ldots\ldots > \ldots\ldots\ldots\ldots\ldots$ most acidic \hfill least acidic

(b(i))[3]

Three carboxylic acids, methanoic acid, $\text{HCO}_2\text{H}$, ethanedioic acid, $\text{HO}_2\text{CCO}_2\text{H}$, and butanedioic acid, $\text{HO}_2\text{CCH}_2\text{CH}_2\text{CO}_2\text{H}$, are considered. Two tests were performed on separate samples of each organic acid, as shown. The results obtained were as follows (\checkmark = observed change, \times = no observed reaction). Fill in the table with the reagents and conditions and the observation for a positive test. Assume that these organic acids all have similar acid strength.

(b(ii))[2]

Each compound, $\text{HCO}_2\text{H}$, $\text{HO}_2\text{CCO}_2\text{H}$ and $\text{HO}_2\text{CCH}_2\text{CH}_2\text{CO}_2\text{H}$, is dissolved separately in $\text{CDCl}_3$. Proton ($^1\text{H}$) NMR and carbon-13 ($^{13}\text{C}$) NMR spectra are then obtained. Complete the table.

(b(iii))[1]

The proton NMR spectrum of $\text{HCO}_2\text{H}$ in $\text{D}_2\text{O}$ is obtained. Describe and explain how this spectrum differs from the proton NMR spectrum of $\text{HCO}_2\text{H}$ in (b)(ii).

(ii)[2]

Each compound, $\text{HCO}_2\text{H}$, $\text{HO}_2\text{C CO}_2\text{H}$ and $\text{HO}_2\text{CCH}_2\text{CH}_2\text{CO}_2\text{H}$, is dissolved separately in $\text{CDCl}_3$. Proton ($^1\text{H}$) NMR and carbon-13 ($^{13}\text{C}$) NMR spectra are then obtained. Complete the table showing the number of peaks in the proton NMR and the number of peaks in the carbon-13 NMR for each compound.

(iii)[1]

The proton NMR spectrum of $\text{HCO}_2\text{H}$ in $\text{D}_2\text{O}$ is obtained. Describe and explain how this spectrum differs from the proton NMR spectrum of $\text{HCO}_2\text{H}$ in (b)(ii).

(c(i))[2]

$1,4$-dibromobutane, $\text{Br(CH}_2)_4\text{Br}$, is used in the synthesis of the dicarboxylic acid $\text{J}$ and diamine $\text{K}$ as shown. Draw the structures of $\text{G}$ and $\text{H}$ in the boxes.

(c(ii))[4]

Suggest reagents and conditions for steps 1 to 4.

(d)[2]

Polyamide $\text{L}$ can be synthesised from dicarboxylic acid $\text{J}$, $\text{HO}_2\text{C(CH}_2)_2\text{CO}_2\text{H}$, and diamine $\text{K}$, $\text{H}_2\text{N(CH}_2)_6\text{NH}_2$. Draw the repeat unit of the polymer formed in the box. Any functional groups should be shown displayed.

Worked solution & mark scheme

This 21-mark question has a full step-by-step worked solution and mark scheme. One marking point: ethanoic acid > butanoic acid > water > ethanol

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