Carbonyl Compounds Flashcards
What are the most common carbonyl compounds?
Aldehydes and ketones
What bond is the carbonyl group of the compound able to form?
Hydrogen bonds with water. Therefore carbonyl groups are soluble in water
How are aldehydes oxidised?
Initially oxidised from primary alcohols.
If it is performed under reflux, primary alcohols will be oxidised further to produce carboxylic acids.
Check equation on pmt
How are ketones formed?
Secondary alcohols can be oxidised to ketones when heated in the presence of acidified potassium dichromate
How can aldehydes and ketones form alcohols?
Nucleophilc Addition
A reducing agent of NaBH4 is used.
It provides an H: nucleophile.
first a salt is formed, and then a dilute acid is added to release the alcohol from the salt.
What happens when NaCN and an Aldehyde or a ketone reacts?
Nucleophilic Addition
:CN- nucleophile
H+ is also required. HCN would be used but it is hard to store and is a toxic gas which reacts to produce dangerous byproducts.
this then forms a hydroxynitrile
Draw a two step mechanism for the nucleophilc addition reaction between NaCN and either and aldehyde or a ketone.
Check pmt
Draw a mechanism for NaBH4 and an aldehyde or a ketone
Check pmt
How can the presence of a carbonyl compound be detected?
Using 2,4-dinitrophenylhydrazine a yellow, orange or reddish-orange precipitate will form.
The exact colour depends on the identity of the compound.
Alcohols and other molecules which don’t contain carbonyl groups do not produce a precipitate.
How can specific aldehydes/ketones be identified?
By using 2,4-DNP a precipitate will form.
The solid is then purified though recrystallisation.
The melting point of the pure crystals formed can then be compared with the melting points of 2,4dinitrophenylhydrazones of all common aldehydes and ketones.
How can I identify that a compound contains Aldehydes?
Using Tollen’s reagent
A layer of silver will form.
If a ketones is present the solutions will remain colourless.
How does Tollen’s reagent work?
It is ammoniacal silver nitrate. It oxidises the aldehyde to a carboxylic acid and reduces silver ions to silver in the presence of an aldehyde.
