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Topic 6: Organic Chemistry I - Introduction, Alkanes and Alkenes

Quick questions on Organic Chemistry I: Alkanes and Alkenes (Topic 6) - Edexcel A-Level Chemistry

4short 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 alkane reactions?
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Alkanes are saturated and fairly unreactive (strong, non-polar C-C\text{C-C} and C-H\text{C-H} bonds). They undergo: - Complete combustion to CO2\text{CO}_2 and H2O\text{H}_2\text{O} in plenty of oxygen. - Incomplete combustion to CO\text{CO} (toxic) or soot when oxygen is limited. - Free-radical substitution with halogens in UV light, by a three-stage mechanism: initiation (homolytic bond fission of X2\text{X}_2 forming radicals), propagation (chain-carrying steps that regenerate a radical), and termination (two radicals combine to end the chain).
What are alkene reactions?
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The C=C\text{C=C} double bond is electron-rich (a pi bond above and below the sigma bond) and attracts electrophiles, so alkenes undergo electrophilic addition with Br2\text{Br}_2 (the test for unsaturation, orange to colourless), HBr\text{HBr}, and H2O\text{H}_2\text{O} (steam with a phosphoric acid catalyst, to make alcohols).
What is q1?
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Name the three stages of the free-radical substitution mechanism. [3 marks]
What is q2?
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Predict the major product of the reaction between propene and hydrogen bromide, and explain your choice. [3 marks]

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