Flashcards · 9701 · AS Topic 19

Nitrogen compounds (AS Level) flashcards

8 cards on AS Topic 19, subtopics 19.1 to 19.2. Pick a subtopic or study them all.

Study mode needs JavaScript. Every card is listed below, so you can still cover the answers and test yourself.

All 8 cards

For a quick read-through or printing. Cover the right-hand side to test yourself.

How is a primary amine made from a halogenoalkane?: Heat with excess ammonia in ethanol under pressure (sealed tube). e.g. CH₃CH₂Br + 2NH₃ → CH₃CH₂NH₂ + NH₄Br
Why must ammonia be in excess when making a primary amine?: The primary amine is itself a nucleophile and would react further with the halogenoalkane, giving secondary and tertiary amines and quaternary salts.
What type of reaction forms an amine from a halogenoalkane?: Nucleophilic substitution: the lone pair on NH₃ attacks the δ+ carbon and the halide ion leaves.

Two ways to make nitriles (AS): Halogenoalkane + KCN in ethanol, heat under reflux → nitrile. Aldehyde or ketone + HCN with KCN → hydroxynitrile. Both add one carbon.
Hydrolysis of a nitrile with acid and with alkali: Dilute HCl, reflux: carboxylic acid + ammonium salt. Dilute NaOH, reflux: carboxylate salt + ammonia; then acidify to get the acid.
CN⁻ gives substitution with halogenoalkanes but addition with carbonyls. Why?: Halogenoalkane: sp³ carbon with a leaving group, so the halide leaves (substitution). Carbonyl: sp² carbon with a π bond and no leaving group, so the π bond breaks (addition).
Why does HCN with butanone give equal amounts of two enantiomers, but propanone does not?: The carbonyl carbon is planar, so CN⁻ attacks either face equally. Butanone has two different groups, so a chiral centre forms. Propanone has two identical CH₃ groups, so its product has no chiral centre.
Route: bromoethane → 2-hydroxypropanenitrile: 1 NaOH(aq), heat → ethanol. 2 Acidified K₂Cr₂O₇, distil → ethanal. 3 HCN with KCN → CH₃CH(OH)CN.