Chemical reactions of the alkenes
4 marks · NormalButene (C4H8) is an alkene that can undergo combustion and addition reactions.
Write the balanced chemical equation for the complete combustion of butene (C4H8) in oxygen.
Describe what happens to the C=C double bond when butene reacts with bromine, Br2.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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(a)
(b) The C=C double bond breaks and bromine atoms add to the carbons. Product is a dibromo compound.
Common mistakes: Incorrect coefficients in combustion equation; Not mentioning that double bond breaks in addition reaction
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Marking points
M1 (a) · 1 mark · Writes a correct unbalanced equation or correct formulae for reactants and products.
A1 (a) · 1 mark · Equation is correctly balanced:
B1 (b) · 1 mark · States that the C=C double bond breaks (or opens).
B2 (b) · 1 mark · States that bromine atoms add to the carbons (or product is a dibromo compound).
Worked solution
a)
b) The C=C double bond breaks. Each carbon becomes bonded to a bromine atom, forming a dibromo compound.