A couple of key points:
- Aldehydes and Ketones both contain a carbonyl group, but are also less reactive than acid chlorides.
- They do NOT react with organocopper reagents and weak hydride donors (as these weak reagents are involved in their own synthesis).
- The reactions are addition rather than substitution as there is no leaving group.
- They have one less bond to an electronegative atom than acid chlorides (no chlorine!).
They can be formed through reduction of Acid Chloride:
If an aromatic ring is being substituted then we must use friedel crafts acylation.
For Acid Chloride to Aldehyde we use Bu3SnH as a source of weak Hydride ions which displace a Cl-. We do not use a more obvious source such as LiAlH4 as this will result in the over reduction of the aldehyde into a primary alcohol.
For Acid Chloride to Ketone we use R’2CuLi as a source of nucleophilic R’ group.
and via reactions with Alcohols:
Simply, Primary alcohols lead to Aldehydes and secondary alcohols lead to Ketones when reacted with PCC. This is oxidation.
and finally with Alkanes:
Alkanes are just as simple as alcohols – just add O3 then PPh3 for an easy reaction!
Simple alkenes lead to aldehydes and more complex lead to ketones.
From Acid Chloride to Aldehyde – Bu3SnH (as a source of H-)
From Acid Chloride to Ketone – R2CuLi (as a source of R)
From Alcohol to Aldehyde/Ketone – PCC
From Alkene to Aldehyde/Ketone – O3 then PPh3
– Reactions with Carbon Nucleophiles and Hydride Donors
As mentioned earlier, aldehydes and ketones do not react with weak hydride donors (eh Bu3SnH) or organocopper reagents (eg R2CuLi) – they need more powerful reagents.
These come in the form of Grignard reagents (eg RMgBr) and powerful halide donors (eg LiAlH4).