Acylation

Question 1

What happens during acylation?

Answer 1

the process by which the acyl group (R-C=O) from an acylating agent (eg. acyl chlorides) is incorporated into the nucleophile by replacing the H that is on the O of an alcohol or the N of an amine/ammonia in the nucleophile

Question 2

What are acylating agents?

Answer 2

acyl chlorides or acid anhydrides

Question 3

Draw the general chemical equation of water + acyl chlorides.

Answer 3

Question 4

Draw the general mechanism for water + acyl chlorides

Answer 4

Question 5

Draw the general chemical equation of alcohols + acyl chlorides

Answer 5

Question 6

Draw the general mechanism for alcohols + acyl chlorides

Answer 6

Question 7

Draw the general chemical equation for ammonia + acyl chlorides

Answer 7

Question 8

Draw the general mechanism for ammonia + acyl chlorides

Answer 8

(you need 2 ammonia)

Question 9

Draw the general chemical equation for amine + acyl chlorides

Answer 9

Question 10

Draw the general mechanism for amines + acyl chlorides

Answer 10

(you need 2 amine)

Question 11

Draw the general chemical equation of water + acid anhydrides

Answer 11

the product is 2 carboxylic acid

Question 12

Draw the general chemical equation of alcohol + acyl anhydrides

Answer 12

Question 13

Draw the general chemical equation of ammonia + acyl anhydrides

Answer 13

Question 14

Draw the general chemical equation of amine + acyl anhydrides

Answer 14

Question 15

State two advantages and two disadvantages (compared to carboxylic acids aka esterification) of using acyl chlorides in the preparation of esters.

Answer 15

Advantages:

The reaction is a non-reversible reaction with a good yield, hence it is a more efficient method of making an ester than making alcohol with a carboxylic acid.

The reaction happens at room temperature, unlike carboxylic acids. Therefore, it saves energy.

Disadvantages:

Acyl chlorides are very reactive compounds and react vigorously. They can react with the water at the surface of the eye producing HCl and organic acids irritating the eye. Hence, they are more dangerous to use in labs than propanoic acid.

Typically, acyl chlorides are synthesised from acid anydrides, themselves synhesised from esters, presumably synthesised from carboxcylic acids. So you are really adding an extra 3 steps to the reaction, each of which will be less than 100% efficient.

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Question 16

Why are acid anhydrides often used instead of acid chlorides?

Answer 16

• cheaper
• less corrosive
• less vulnerable to hydrolysis as acid chlorides are very reactive and can react to the moisture in the air
• less dangerous to use

Question 17

Why are acid chlorides so corrosive?

Answer 17

c-cl bond is very electronegative so the chlorine leaves more easily (the chlorine is a very good leaving group)

Question 18

How is asprin made?

Answer 18

by reacting salicylic acid with ethanoic anhydride or ethanoyl chloride

Question 19

Why is ethanoic anhydride used in industry to make asprin rather than ethanoyl chloride?

Answer 19

• cheaper
• after due to being less corrosive and reacting more slowly with water
• doesn’t produce dangerous hydrogen chloride fumes

Question 20

Draw the equation to make asprin (with ethanoic anhydride)

Answer 20