We carried out a great lab in school today, making esters. Have you ever done this? What was good about it was that we used a good range of reagents and got some very different results.
I set the class up with a range of alcohols and carboxylic acids and told them it was up to them what they wanted to make.
We used microscale quantities for two important reasons:
1, As a safety precaution
The beauty of using the microscale quantities is that I could get away with using 2 mol dm-3 sulfuric acid instead of concentrated sulphuric acid.
2, Students could also potentially use butan-1-ol and butanoic acid (more on this later).
The students were told to use a plastic dropper to measure out 10 drops of alcohol and 10 drops of carboxylic acid. This was then added to 10cm3 of the 2 mol dm-3 sulfuric acid. The boiling tube was appropriately labelled and the ester and catalyst mixture was heated in a water bath at 50 oC for approx. 10 – 15 min. During this heating time students were encouraged to make esters using other combinations of alcohols and carboxylic acids. At the end of the heating process, the solution was put into an excess of saturated sodium carbonate solution to neutralise any unread sulphuric acid catalyst and carboxylic acid.
The following reagents were available for the students to react:
Ethanol, Propan-1-ol, Propan-2-ol and Butanol-1-ol
Ethanoic acid, Propanoic acid, Butanoic acid
Anything that involved Butanoic acid or Butan-1-ol was heated in the fume cupboard as a safetly precaution. This is because Butanoic acid smells of vomit and to me Butan-1ol smells of body odour (not everyone agrees with this analogy but everyone does agree that Butan-1-ol smells really bad!).
Bad smells aside, the results were great and the pleasant fruity smells of the different esters soon outweighed the bad smells generated by Butanoic acid and Butan-1-ol.
And the best ester to make? Well, Butyl butanoate is in my opinion the best. It is made from two really dad smelling reagents but smells of pineapples and has a very pleasant odour.
NB – if you do decide to make esters following this method it is up to you, the teacher to adequately risk asses the practical and brief the students.
What method do you use to make esters? There are some larger and grander methods out there so what do you do? It would be great to read your ideas below.