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CAIE A-Level Chemistry 14.2.1 Preparation of Alkenes

Practise preparing alkenes by eliminating HX, dehydrating alcohols or cracking longer-chain alkanes.

Syllabus
2028–2030
Course
Chemistry 9701
Level
AS

Exam points

  • eliminate HX from a halogenoalkane using ethanolic NaOH and heat to form C=C
  • dehydrate an alcohol with hot Al2O3 or concentrated H2SO4 or H3PO4 and heat
  • crack a longer alkane with heat and Al2O3, balancing products that include an alkene

14.2.1—Preparation of alkenes question 1

[Maximum number: 1]

Species such as NH4+,CO32−\mathrm{NH}_{4}{ }^{+}, \mathrm{CO}_{3}{ }^{2-} and PO43−\mathrm{PO}_{4}{ }^{3-} are examples of molecular ions.

OH−(aq)\mathrm{OH}^{-}(\mathrm{aq}) reacts with 2-bromo-2-methylpropane in an SN1\mathrm{S}_{\mathrm{N}} 1 reaction. The molecular ion (CH3)3C+\left(\mathrm{CH}_{3}\right)_{3} \mathrm{C}^{+}forms as the intermediate in this reaction.

Organic compound M forms when 2-bromo-2-methylpropane is heated with ethanolic OH−\mathrm{OH}^{-}.

Draw the structure of M.

Figure for Question 14.2.1—Preparation of alkenes question 1 — CAIE A-Level Chemistry AS
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