(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: 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 ]

(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 ]

[Maximum number: 8]

One reason for the wide variety of organic compounds is isomerism, either structural isomerism or stereoisomerism.

(a)

(i)

Explain the meaning of the term structural isomerism.

[ 2 ]

(ii)

Explain the meaning of the term stereoisomerism.

[ 2 ]

(b)

Pent-1-ene, $\mathrm{CH}_{2}=\mathrm{CH}\left(\mathrm{CH}_{2}\right)_{2} \mathrm{CH}_{3}$ , does not show stereoisomerism.

[ 4 ]

(i)

Give two reasons why pent-1-ene does not show stereoisomerism. reason 1
reason 2

[ 2 ]

(ii)

A different structural isomer of pent-1-ene shows geometrical isomerism.

Draw the structure of one of the two geometrical isomers with the formula $\mathrm{C}_{5} \mathrm{H}_{10}$ .
Give the full name of this isomer.

[ 2 ]

[Maximum number: 5]

G belongs to a group of compounds called ethers.

Fig. 3.1

(a)

The functional group in G is an oxygen atom bonded to two carbon atoms.

Fig. 3.3

G, H and J are structural isomers with molecular formula $\mathrm{C}_{4} \mathrm{H}_{10} \mathrm{O}$ . H and J are straight chain molecules.

Table 3.3 shows the boiling points and reactions of G, H and J when heated under reflux with excess acidified $\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}$ .

Table 3.3

[ 5 ]

(i)

Identify the type of structural isomerism shown between G and H using the information in Table 3.3.

[ 1 ]

(ii)

Identify the type of structural isomerism shown between H and J using the information in Table 3.3.

[ 1 ]

(iii)

Draw a possible structure for H and for J. State the systematic name for each structure.

```
J
name
```

[ 3 ]