Carbonyls, carboxylic acids and esters. Flashcards
Aldehyde classification.
Carbonyl functional group found at the end of the carbin chain
Carbon atom of carbonyl group is attached to 1 or 2 H atoms
CHO.
Carbonyl functional group.
C=O.
Ketones classification.
Carbonyl functional group is attached to 2 carbon atoms in the carbon chain
CO.
Rules for naming carbonyl compounds.
Add a suffix to the stem of the longest carbon chain
-al for an aldehyde
-one for a ketone
In an aldehyde the carbon atom of the carbonyl group is always carbon 1
In a ketone the carbonyl carbon atom needs to be numbered.
Oxidation of aldehydes.
Oxidised to carboxylic acids
When refluxed with dichromate(VI) ions, Cr2O7(2-)/H+.
Oxidiation of ketones.
Do not undergo oxidation reactions
Can help distinguish between these.
Why is carbonyl reactivity different to alkene reactivity?
C=C bond in alkenes is non-polar
C=O bond in carbonyls is polar.
Why is the C=O bond polar?
O is more electronegative than C
e- density in the bond lies closer to O than the C atom
C end is slightly positive and O end slightly negative.
What does a nucleophile do?
Is attracted to and attacks the C + atom resulting in addition across the double bond
Nucleophilic addition.
Reducing an aldehyde.
NaBH4 is used as a reducing agent
Reduced to a primary alcohol.
Reducing a ketone.
Reduced to secondary alcohols
By NaBH4.
Explanation for the mechanism for the reaction w/ NaBH4.
Explanation for the mechanism for the reaction w/ NaCN/H+.
How to detect the presence of a carbonyl group.
2,4-DNP/brady’s reagant
In the presence of a carbonyl group, a yellow or orange precipitate is formed.
Distinguishing between aldehydes and ketones.
A fresh sample of the compound can be classified using Tollen’s reagant-solution of silver nitrate in aq ammonia
Aldehyde group=silver mirror produced
Acts as an oxidising agent
Silver ions are reduced to silver
Aldehyde oxidised to carboxylic acid.
