Chemistry (AS Level)·Carbonyl compounds · NSSCAS 4.6.1
Aldehydes & Ketones
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Meet the carbonyl compounds — the aldehydes and ketones. Learn the carbonyl group C=O, how an aldehyde (–CHO at the end) differs from a ketone (C=O in the middle), how to read and draw their displayed, condensed and skeletal formulae, how to name them up to six carbons, how to deduce a molecular formula from a structure, and how they are made by oxidising primary and secondary alcohols with acidified potassium dichromate — watching the orange-to-green colour change.
What you'll learn in this lesson
By the end you should be able to (NSSCAS Chemistry (AS Level) 4.6.1):
- Interpret and use general, structural (condensed/semi-structural and displayed) and skeletal formulae of aldehydes and ketones, recognising the carbonyl group C=O
- Distinguish an aldehyde (C=O at the end of the chain, carrying an H, –CHO) from a ketone (C=O in the middle, –CO–)
- Name aldehydes and ketones up to six carbons, e.g. propanal, butanal, propanone, pentan-2-one
- Deduce the molecular formula of an aldehyde or ketone from a given structure
- Describe the formation of aldehydes from primary alcohols and ketones from secondary alcohols using Cr₂O₇²⁻/H⁺, including the orange→green colour change and the distinction that aldehydes can be oxidised further but ketones cannot
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