Nitriles & Hydroxynitriles (CIE A Level Chemistry)

Propanal undergoes nucleophilic addition with a mixture of HCN and NaCN to make 2-hydroxybutanenitrile, CH₃CH₂CH(OH)CN.

The mechanism for this reaction occurs in two main steps. The first step involves a nucleophile attacking the carbonyl carbon of propanal.

Explain which species acts as the nucleophile during this reaction. 

The second step in the mechanism involves an intermediate species, CH₃CH₂C(O)HCN^–, reacting with HCN to form 2-hydroxybutanenitrile.

Draw the mechanism for this step.

• Identify the intermediate species that reacts with HCN.
• Include all charges, partial charges, lone pairs and curly arrows. 

The structure of the 2-hydroxybutanenitrile product is shown in Fig. 1.1.

Predict the values for the bond angles a and b shown in the diagram.

The product 2-hydroxybutanenitrile exists as a pair of stereoisomers.

Two students try to prepare butanoic acid from a halogenoalkane in the laboratory.

Both students perform a nucleophilic substitution reaction to form P in reaction 1 of Fig. 2.1.

They both form butanoic acid from P but student A uses a single reaction, while student B uses two reactions.

Fig. 2.1

Student A converts P into butanoic acid in a single step, reaction 2.

Student B converts P into Q using dilute sodium hydroxide in reaction 3. This is followed by acidification of the product in reaction 4 to form butanoic acid.

Draw the structural formula of Q.

Explain why it is likely that student A will have a higher overall yield of butanoic acid from their halogenoalkane than student B.

Halogenoalkanes are often used as intermediates in organic reactions.

Three reactions of bromoethane, CH₃CH₂Br, are shown if Fig. 3.1.

Fig. 3.1

For each reaction, state the reagent and solvent used.

Reactions 1 and 3 require specific reaction conditions to occur as shown in Fig. 3.1.

For each reaction, give another solvent and the alternative product that will be formed.

The product of reaction 2 can be converted into CH₃CN.

The product of reaction 3 can be used to produce propanoic acid by two different hydrolysis reactions.

Compare the two types of hydrolysis reaction in the production of propanoic acid from the product of reaction 3.

2-hydroxy-2-phenylpropanenitrile is shown in Fig. 1.1.

Fig. 1.1

Deduce the number of sigma (σ) and pi (π) bonds in 2-hydroxy-2-phenylpropanenitrile.

A molecule of 2-hydroxy-2-phenylpropanenitrile contains sp, sp² and sp³ hybridised carbon atoms.

State the number of sp, sp² and sp³ hybridised carbon atoms in a molecule of 2-hydroxy-2-phenylpropanenitrile.

2-hydroxy-2-phenylpropanenitrile can be produced from compound X, a secondary alcohol, in a two-step synthesis.

compound X

compound Y

State the reagents and conditions required for step 1 and step 2.

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2,2-dimethylpentanenitrile is useful in the synthesis of a variety of medicines and pharmaceuticals. 

Draw the skeletal formula of 2,2-dimethylpentanenitrile.

2,2-dimethylpentanenitrile undergoes hydrolysis when heated with dilute hydrochloric acid.

Write an equation for the hydrolysis of 2,2-dimethylpentanenitrile.

2,2-dimethylpentanoic acid can also be produced by the hydrolysis of 2,2-dimethylpentanenitrile using sodium hydroxide but this occurs in two steps.

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