(a)

The reaction between propane and chlorine produces a mixture of many compounds, four of which are structural isomers with the molecular formula $\mathrm{C}_{3} \mathrm{H}_{6} \mathrm{Cl}_{2}$ .
Draw the structural or skeletal formulae of these isomers, and indicate any chiral atoms with an asterisk (*).

[ 3 ]

[Maximum number: 3]

Methylpropane, $\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CHCH}_{3}$ , is an isomer of butane, $\mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{2} \mathrm{CH}_{3}$ .

(a)

(i)

Explain why methylpropane and butane are a pair of isomers.

[ 2 ]

(ii)

Identify the type of isomerism shown by methylpropane and butane.

[ 1 ]

[Maximum number: 4]

Combustion data can be used to calculate the empirical formula, molecular formula and relative molecular mass of many organic compounds. Combustion data cannot distinguish between different structural isomers.

(a)

Define the term structural isomers.

[ 2 ]

(b)

P is a hydrocarbon, $\mathrm{C}_{x} \mathrm{H}_{y^{\prime}}$ . A gaseous sample of P occupied a volume of $25 \mathrm{~cm}^{3}$ at $37^{\circ} \mathrm{C}$ and 100 kPa .

The sample was completely burned in $200 \mathrm{~cm}^{3}$ of oxygen (an excess).
The final volume, measured under the same conditions as the gaseous sample (so that the water produced is liquid and its volume can be ignored), was $150 \mathrm{~cm}^{3}$ .

Treating the remaining gaseous mixture with concentrated alkali, to absorb carbon dioxide, decreased the volume to $50 \mathrm{~cm}^{3}$ .

The equation for the complete combustion of P can be represented as shown.

\mathrm{C}_{x} \mathrm{H}_{y}+\left(x+\frac{y}{4}\right) \mathrm{O}_{2} \rightarrow x \mathrm{CO}_{2}+\frac{y}{2} \mathrm{H}_{2} \mathrm{O}

[ 2 ]

(i)

P is unbranched.

Give the skeletal formulae for two possible structures of P that are positional isomers of each other.

[ 2 ]

[Maximum number: 2]

Combustion data can be used to calculate the empirical formula, molecular formula and relative molecular mass of many organic compounds.

(a)

T is an alcohol, $\mathrm{C}_{x} \mathrm{H}_{y} \mathrm{O}$ . A gaseous sample of T occupied a volume of $20 \mathrm{~cm}^{3}$ at $120^{\circ} \mathrm{C}$ and 100 kPa .

The sample was completely burned in $200 \mathrm{~cm}^{3}$ of oxygen (an excess). The final volume, measured under the same conditions as the gaseous sample, was $250 \mathrm{~cm}^{3}$ .

Under these conditions, all water present is vaporised. Removal of the water vapour from the gaseous mixture decreased the volume to $170 \mathrm{~cm}^{3}$ .

Treating the remaining gaseous mixture with concentrated alkali, to absorb carbon dioxide, decreased the volume to $110 \mathrm{~cm}^{3}$ .

The equation for the complete combustion of T can be represented as shown.

\mathrm{C}_{x} \mathrm{H}_{y} \mathrm{O}+z \mathrm{O}_{2} \rightarrow x \mathrm{CO}_{2}+\frac{y}{2} \mathrm{H}_{2} \mathrm{O}

[ 2 ]

(i)

Give the skeletal formulae for two possible structures of T.

Name each alcohol.

[ 2 ]

[Maximum number: 2]

Compound A is an organic compound which contains carbon, hydrogen and oxygen.
When 0.240 g of the vapour of A is slowly passed over a large quantity of heated copper(II) oxide, CuO , the organic compound A is completely oxidised to carbon dioxide and water. Copper is the only other product of the reaction.

The products are collected and it is found that 0.352 g of $\mathrm{CO}_{2}$ and 0.144 g of $\mathrm{H}_{2} \mathrm{O}$ are formed.

(a)

Compound A is a liquid which does not react with 2,4-dinitrophenylhydrazine reagent or with aqueous bromine.

Suggest two structural formulae for A.

[ 2 ]

[Maximum number: 1]

The structures represent three compounds, each with four carbon atoms per molecule.

Which row is correct?

lowest

boiling point

$\longrightarrow$

highest

boiling point

X

Y

Z

Y

X

Z

X

Y

Z

Y

X

[Maximum number: 3]

The molecular formula $\mathrm{C}_{3} \mathrm{H}_{6}$ represents the compounds propene and cyclopropane.

propene

cyclopropane

(a)

Under suitable conditions, propene and cyclopropane each react with chlorine.

[ 3 ]

(i)

When cyclopropane reacts with chlorine, three different compounds with the molecular formula $\mathrm{C}_{3} \mathrm{H}_{4} \mathrm{C} l_{2}$ can be formed.

Draw displayed structures of each of these three compounds.

[ 3 ]

[Maximum number: 12]

When 0.42 g of a gaseous hydrocarbon A is slowly passed over a large quantity of heated copper(II) oxide, CuO, A is completely oxidised.

The products are collected and it is found that 1.32 g of $\mathrm{CO}_{2}$ and 0.54 g of $\mathrm{H}_{2} \mathrm{O}$ are formed. Copper is the only other product of the reaction.

(a)

(i)

It is thought that A is an alkene rather than an alkane.

Use your answers to (i) and (ii) to deduce whether this is correct.
Explain your answer.

[ 5 ]

(b)

Analysis of another organic compound, B, gave the following composition by mass: $\mathrm{C}, 64.86 \% ; \mathrm{H}, 13.50 \%, \mathrm{O}, 21.64 \%$ .

[ 7 ]

(i)

The empirical and molecular formulae of B are the same.

B is found to be chiral.
Draw displayed formulae of the two optical isomers of this compound, indicating with an asterisk (*) the chiral carbon atom.

(ii)

There are three other structural isomers of B which are not chiral but which contain the same functional group as B.

In the boxes below, draw the structural formulae of these isomers. \begin{tabular}{|l|l|l|}
\hline & & \\
\hline
\end{tabular}

[ 7 ]

(a)

When heated with HCl(aq), organic isocyanates, RNCO , are hydrolysed to the amine salt, $\mathrm{RNH}_{3} \mathrm{Cl}$ , and $\mathrm{CO}_{2}$ .

\mathrm{RNCO}+\mathrm{H}_{2} \mathrm{O}+\mathrm{HCl} \rightarrow \mathrm{RNH}_{3} \mathrm{Cl}+\mathrm{CO}_{2}

A1.00 g sample of an organic isocyanate, RNCO, was treated in this way, and the $\mathrm{CO}_{2}$ produced was absorbed in an excess of aqueous $\mathrm{Ba}(\mathrm{OH})_{2}$ according to the equation shown. The solid $\mathrm{BaCO}_{3}$ precipitated weighed 1.66 g .

\mathrm{Ba}(\mathrm{OH})_{2}(\mathrm{aq})+\mathrm{CO}_{2}(\mathrm{~g}) \rightarrow \mathrm{BaCO}_{3}(\mathrm{~s})+\mathrm{H}_{2} \mathrm{O}(\mathrm{l})

[ 1 ]

(i)

Suggest a possible structure of the amine $\mathrm{RNH}_{2}$ , which forms the amine salt, $\mathrm{RNH}_{3} \mathrm{Cl}$ . □

[ 1 ]

(a)

(i)

There are two isomers of $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CHClCH}_{3}$ that have fewer peaks in their carbon-13 NMR spectra than $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CHClCH}_{3}$ .

Draw the structures of the isomers and state the number of peaks for each isomer.
isomer 1
isomer 2
number of peaks = number of peaks =

[ 3 ]