9701 · 19.2
Nitriles and hydroxynitriles flashcards
Revision flashcards for Cambridge 9701 Nitriles and hydroxynitriles (syllabus 19.2). Flip, recall, then mark a real past-paper question.
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What is the functional group of a nitrile?
The –C≡N group, where a carbon atom is triple-bonded to a nitrogen atom.
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What are the reagents and conditions to form a nitrile from a halogenoalkane?
Reagent: Potassium cyanide (KCN) dissolved in ethanol. Conditions: Heat under reflux.
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What type of reaction is the formation of a nitrile from a halogenoalkane?
Nucleophilic substitution.
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Why is an ethanolic solvent used instead of an aqueous one when forming a nitrile from a halogenoalkane?
To minimise the competing elimination reaction (where CN⁻ acts as a base) and to prevent hydrolysis of the halogenoalkane by water, which is a competing nucleophile.
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What are the reagents to form a hydroxynitrile from an aldehyde?
Potassium cyanide (KCN) or sodium cyanide (NaCN) followed by a dilute acid (e.g., H₂SO₄). This generates toxic HCN in situ.
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What type of reaction is the formation of a hydroxynitrile from a carbonyl compound?
Nucleophilic addition.
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What are the products of the acid hydrolysis of propanenitrile?
Propanoic acid (CH₃CH₂COOH) and an ammonium salt (e.g., ammonium chloride if HCl is used).
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What are the reagents and conditions for the acid hydrolysis of a nitrile?
Reagent: Dilute aqueous acid (e.g., HCl(aq) or H₂SO₄(aq)). Conditions: Heat under reflux.
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What is the product of the reduction of butanenitrile (CH₃CH₂CH₂CN)?
Butylamine (CH₃CH₂CH₂CH₂NH₂), a primary amine.
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What is a suitable reducing agent for converting a nitrile to a primary amine?
Lithium tetrahydridoaluminate (LiAlH₄) in dry ether, followed by an aqueous workup.
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Why does the reaction of propanal with KCN/H⁺ produce a racemic mixture?
Propanal's carbonyl group is planar. The CN⁻ nucleophile can attack from above or below the plane with equal probability, forming two non-superimposable mirror images (enantiomers) in equal amounts.
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What is the key synthetic utility of reactions forming nitriles?
They increase the length of the carbon chain by exactly one carbon atom.