26.5 Acylation Flashcards
What is acylation
what is acyl group
It is the process where the acyl group is introduced to another molecule
An acyl group R- C=O
What are acid derivitives
Group of compounds that all have acyl group as part of their structure
Eg acid chlorides and acid anhydrides
Acid derivitives may come from carboxylic acids
How do acid derivatives react
The acyl group is polarised so the C is f+ and the O is f-
So it is Z-C=O and R group also attached
It is attacked by nucleophiles at the C f+ so as a result the C-Z bond breaks so nucleophile therefore acquires the acyl group
so had been acylated
And the :Z- is released from it
What factors affect how the reaction of acylation occurs
1) The magnitude of the f+ on the carbonyl atom which in turn depends on the electron releasing or attracting power of z
2) How easily z is lost
3) How good the nucleophile is
What is an example of an acid derivitive
What do z groups do
Acid chlorides have Cl as the z group and also acid anhydrides
Z groups withdraw electrons from the carbonyl atom, which makes the carbon more positive so makes them more reactive towards nucleophiles
What are some good nucleophiles used in these acylation reactions
Nucleophiles must have a lone pair of electrons to attack f+ carbon
Best nucleophile is a primary amine with N: connected to two hydrogens and R group
Then, ammonia NH3 with lone pair, then alcohol with oxygen having lone pair then water
What are addition elimination reactions
The reaction of these nucleophiles with acyl chlorides and acyl anhydrides
The nucleophiles here are all neutral so must lose a hydrogen ion at the same time as donating a lone pair
What is reaction of acyl chloride and ammonia as nucleophile
What is reaction of acyl chloride and primary amine as nucleophile
An amide is made so R-C=O with C also attached to NH2
Product is N substituted amide, so the NH2 above is now R-N-H
What is reaction of acyl chloride and alcohol as nucleophile
What is reaction of acyl chloride and water as nucleophile
An ester is formed
carboxylic acid
Why is ethanoic anhydride more useful than ethanoyl chlorid
. Cheaper
.Less corrosive
. Doesn’t react with water as readily
. It is safer and end product is ethanoic acid rather than HCl gas
