CAIE A-Level Chemistry A2 29 An Introduction to a Level Organic Chemistry Questions

Practise the functional-group, structural and reaction conventions needed for advanced organic chemistry questions.

Covered syllabus points

A Level organic chemistry conventions and functional group reference 29.1 Formulas, functional groups and nomenclature 29.2 Characteristic organic reactions 29.3 Shapes of aromatic organic molecules; σ and π bonds 29.4 Optical isomerism

[Maximum number: 1]

Procaine is used as an anaesthetic in medicine. It can be synthesised from methylbenzene in five steps as shown in Fig. 7.1.

Fig. 7.1

Name all the functional groups present in procaine.

[Maximum number: 5]

(a)

Describe the shape of delocalised benzene.

Include the geometry of each carbon, the C-C-H bond angle and the type of bond(s) between the carbon atoms and between the carbon and hydrogen atoms.

[ 2 ]

M1 $120^{\boldsymbol{\circ}}$ AND hexagonal/trigonal planar

M2 C -C has $\pi$ -bonds and $\sigma$ -bonds AND C-H have $\sigma$ -bonds only

(b)

The reaction of phenylethanone with 1,4-dibromobutane, $\mathrm{BrCH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{Br}$ , in the presence of $\mathrm{FeBr}_{3}$ is shown in Fig. 6.2.
phenylethanone

Fig. 6.2

The mechanism of this reaction is similar to that of the alkylation of benzene.

[ 3 ]

(i)

Complete the mechanism in Fig. 6.3 for the reaction of phenylethanone with $\mathrm{BrCH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2}^{+}$ ions.

Include all relevant curly arrows and charges.
Draw the structure of the organic intermediate.

Fig. 6.3

[ 3 ]

Figure for Answer to Question (i) — CAIE A-Level Chemistry A2

$\text { product } \quad+\ldots \mathrm{H}^{+}$

M1 curly arrow from inside the hexagon towards $\mathrm{C}^{+}$

M2 structure of the intermediate

M3 curly arrow from C-H bond into the ring AND $\mathrm{H}^{+}$

[Maximum number: 4]

The amino acid serine, $\mathrm{HOCH}_{2} \mathrm{CH}\left(\mathrm{NH}_{2}\right) \mathrm{COOH}$ , exists in two optically active forms. These optical isomers, isomer P and isomer Q, are shown in Fig. 8.1.

Fig. 8.1

(a)

Isomer P and isomer Q have identical physical and chemical properties, with the exception of two specific properties. One of these two properties is their differing effect on plane polarised light.

State the other property by which they differ.

[ 1 ]

(b)

A solution of pure isomer P of a particular concentration rotates plane polarised light by $5.0^{\circ}$ in a clockwise direction.

Describe how a solution of pure isomer Q of the same concentration affects plane polarised light.

[ 1 ]

rotates plane polarised light $5.0^{\circ}$ in anticlockwise direction

[1]

(c)

Give the term used to describe a mixture containing equal amounts of isomer P and isomer Q.

[ 1 ]

(d)

Describe one way in which a single pure optical isomer of serine can be produced, instead of making a mixture of isomer P and isomer Q.

[ 1 ]

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Covered syllabus points

Question 1

Question 2

Question (a)

Question (b)

Question (i)

Question 3

Question (a)

Question (b)

Question (c)

Question (d)