Some chemical reactions of organic compounds
5 marks · HardThe following reactions involve organic compounds. Answer all parts.
Classify the reaction:
State the reason for your answer in part (a).
Classify the reaction:
State the reason for your answer in part (c).
Classify the reaction:
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(a) Addition
(b) Water is added to ethene with no atoms taken away; all atoms become part of the product.
(c) Substitution
(d) A chlorine atom replaces a hydrogen atom in the molecule; one atom is substituted for another.
(e) Combustion
Also accept: Accept 'burning' for combustion; Accept 'chlorine replaces hydrogen' for substitution
Common mistakes: Misclassifying addition and substitution; Misidentifying products
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Marking points
B1 (a) · 1 mark · Identifies (a) as an addition reaction
B2 (b) · 1 mark · Gives correct reason for addition (nothing removed, atoms added to molecule)
B3 (c) · 1 mark · Identifies (c) as a substitution reaction
B4 (d) · 1 mark · Correct reason for substitution (hydrogen replaced by chlorine)
B5 (e) · 1 mark · Identifies (e) as a combustion reaction
Worked solution
(a) The first reaction is addition because water is added to ethene to give ethanol, with all atoms remaining in the product.
(b) The reason: addition reactions add atoms to an unsaturated molecule, without removing any.
(c) The second reaction is substitution because a chlorine atom replaces a hydrogen atom on propane, producing a new compound and HCl.
(d) In substitution reactions, an atom (chlorine) substitutes a hydrogen atom in the organic molecule.
(e) The third reaction is combustion because butane reacts with oxygen to form carbon dioxide and water.