Halogenoalkanes and nucleophilic substitutionEdexcel A-Level Chemistry: Flashcards

What these 13 flashcards ask

What is a primary halogenoalkane?
What is a tertiary halogenoalkane?
What is a nucleophile?
What is the product of a halogenoalkane with aqueous KOH?
What does aqueous silver nitrate in ethanol show for the halogens?
What are the reagents and product for lengthening the carbon chain?
What happens when a halogenoalkane is heated with excess ammonia in ethanol in a sealed tube?
What reaction happens with ethanolic KOH?
Why is excess ammonia used?
Which halogenoalkane hydrolyses fastest: chloro-, bromo- or iodo-?
Which hydrolyses fastest: primary, secondary or tertiary?
Describe the one-step mechanism of a primary halogenoalkane with OH⁻.
Why is bond enthalpy, not polarity, used to explain the halogen trend?

Exam questions on Halogenoalkanes and nucleophilic substitution

A student has four halogenoalkanes labelled W to Z: 1-bromobutane (W), 2-bromobutane (X), 2-bromo-2-methylpropane (Y) and 1-iodobutane (Z). She plans to warm each with aqueous silver nitrate in ethanol and observe what happens.
Explain, with reference to the role of water, why a precipitate forms when a halogenoalkane is warmed with aqueous silver nitrate in ethanol.2 marks
A chemist wants to lengthen the carbon chain of bromoethane by one carbon atom. She heats bromoethane under reflux with ethanolic potassium cyanide, KCN, and obtains a nitrile.
Describe, in words, the movement of electrons when the cyanide ion reacts with bromoethane in this nucleophilic substitution.2 marks
2-Bromopropane is warmed separately with aqueous potassium hydroxide and with ethanolic potassium hydroxide, giving different organic products. In a separate experiment, bromoethane is heated with a large excess of ammonia dissolved in ethanol, in a sealed tube.
Name the organic product formed with each potassium hydroxide solution and state the role of the hydroxide ion in each reaction.3 marks

Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).