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WAChemistryQuick questions
Unit 4: Organic Chemistry and Chemical Synthesis
Quick questions on Addition reactions of alkenes: WACE Year 12 Chemistry
5short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What are addition to unsymmetrical alkenes?Show answer
When an unsymmetrical reagent (such as HBr or water) adds to an unsymmetrical alkene (such as propene), two products are possible depending on which carbon gains the hydrogen. The major product is usually the one where the hydrogen adds to the carbon that already has more hydrogens (Markovnikov's rule), giving the more substituted product. At WACE level you should recognise that two products are possible and identify the major one.
What is hydrogenation?Show answer
With a nickel or platinum catalyst, hydrogen adds across the double bond to give the saturated alkane:
What is halogenation?Show answer
A halogen adds across the double bond, with no catalyst or light needed. The rapid decolourising of orange bromine water is the standard test for unsaturation:
What is hydration?Show answer
With steam and an acid catalyst (such as phosphoric acid), water adds across the double bond to form an alcohol. This is an industrial route to ethanol:
What is hydrogen halide addition?Show answer
A hydrogen halide adds to give a haloalkane:
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