Carbonyl compounds 26.1 Flashcards
How can aldehydes be oxidized to carboxylic acids?
- Reflux
- with acidified potassium dichromate (Cr2O7 2-/H+)
- usually H2SO4 used as h+ donor
- an oxidising agent
Do ketones undergo oxidation reactions?
- No
- This gives a way to distinguish between aldehydes and ketones
What reaction does the carbonyl group undergo?
Nucleophilic addition
Why does the carbonyl group undergo nucleophilic addition?
Oxygen more electronegative than Carbon.
The electron density lies closer to oxygen atom than to carbon.
This makes carbon end of the bond slightly positive and the oxygen end of the bond slightly negative
How does the carbonyl group undergo nucleophilic addition?
Due to the polarity of carbon oxygen bond, aldehydes and ketones react with some nucleophiles. The nucleophile is attracted to and attacks the slightly positive carbon atom resulting in addition across the c=o bond.
What chemical is used to reduce aldehydes and ketones to alcohols?
NaBH4
How is NaBH4 used to reduce aldehydes and ketones?
Usually warmed with the aldehyde or ketone in aqueous solution
What type of alcohol is produced from a reaction between an aldehyde and NaBH4?
primary alcohol
What type of alcohol is produced from a reaction between a ketone and NaBH4?
secondary alcohol
How does HCN react with carbonyl compounds?
It adds across the double bond.
Why is HCN + carbonyl compound rarely done in labs?
Hydrogen Cyanide is a colourless, extremely poisonous liquid that boils slightly above room temp so it cannot be used safely in an open laboratory.
How is the HCN often produced for the reaction?
Sodium cyanide + sulfuric acid
Why is HCN + carbonyl so useful?
It provides a way of extending the carbon chain
Draw out mechanism for reaction with NaBH4
see p194
Draw out a mechanism for reaction with NaCN/H+
see p195
