Ethanol can be produced by the fermentation of glucose using yeast. Ethanol belongs to a homologous series of organic compounds called alcohols. Explain why ethanol is classified as an alcohol and describe what happens when ethanol is oxidised.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Ethanol is a widely used organic compound found in alcoholic drinks and as a fuel. It is produced industrially and can also be made by the fermentation of glucose.
Model answer (4 marks)
Ethanol contains a hydroxyl group –OH, which is the defining functional group of the alcohol series.
The presence of this –OH group is what classifies ethanol as an alcohol.
When ethanol is oxidised, the –OH group is converted to a carboxyl group –COOH.
The oxidation product is ethanoic acid (acetic acid), which contains the –COOH functional group and is a member of the carboxylic acid homologous series.
The presence of this –OH group is what classifies ethanol as an alcohol.
When ethanol is oxidised, the –OH group is converted to a carboxyl group –COOH.
The oxidation product is ethanoic acid (acetic acid), which contains the –COOH functional group and is a member of the carboxylic acid homologous series.
Examiner tips
- Show the –OH group first to justify the alcohol classification. Mention the conversion to –COOH when describing oxidation. Use the exact terms ‘hydroxyl group’, ‘carboxyl group’, ‘ethanoic acid’. Keep the answer concise – 4 marks only.
- common_mistakes
- :
- Forgetting to mention the –OH group as the defining feature. Saying ethanol oxidises to a ‘ketone’ instead of a carboxylic acid. Using vague terms like ‘oxidised to a more oxidised compound’ without naming ethanoic acid.
Mark scheme (4 marks)
- Ethanol contains the functional group –OH
- The –OH functional group is what defines/characterises the alcohol homologous series
- When ethanol is oxidised, a carboxylic acid is produced
- The product (ethanoic acid) contains the –COOH functional group / is a member of the carboxylic acid homologous series
Key terms in this question
alcohol · oxidised · homologous series
Related
- All OCR GCSE Chemistry A: Gateway Science (J248) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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