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Transcript
NCSU – Dept. of Chemistry – Lecture Demonstrations
Organic Chemistry
Esterification and Odors of Esters
Description: An alcohol and acid are mixed together to generate an ester with a
pleasant odor.
Materials:
Conc. H2SO4
Glacial acetic acid
Salicylic acid
Isoamyl alcohol
Methanol
Ethanol
Plastic pipets
Thin-stemmed pipet
Small cork stoppers
Beaker (for water bath)
Hot plate
Procedure:
Cut the tip off of the plastic pipet and use this as the reaction vessel.
Prepare the following three esters by combining the proper number of drops
(from thin-stemmed pipet) of corresponding alcohol and acid, sealing the vessel
with a cork stopper, and heating at 70-80 oC in a hot water bath for 10 minutes.
After heating, carefully remove the cork stopper and waft vapors of ester to
observe the smell.
Ester
Isoamyl acetate
Ethyl acetate
Methyl salicylate
ROH (# of drops)
Isoamyl (10)
Ethanol (10)
Methanol (20)
Acid (# of drops)
Acetic (10)
Acetic (10)
0.25 g salicylic
H2SO4 (# of drops)
1
1
4
The esters synthesized should have the following scents: isoamyl acetate
(banana), ethyl acetate (fruity), methyl salicylate (wintergreen). A collection of
other “scented” chemicals can be found with the ester synthesis kit in
Dabney 114.
NCSU – Dept. of Chemistry – Lecture Demonstrations
Organic Chemistry
Discussion: These reactions demonstrate a Fischer esterification in which an
alcohol reacts with a carboxylic acid to generate an ester and water as the two
products. The structures of the esters generated in this experiment are shown
below.
HO
O
O
O
O
O
isoamyl acetate
O
ethyl acetate
methyl salicylate
Safety: Wear proper protective equipment including gloves and safety glasses
when preparing and performing this demonstration. Concentrated acids will
cause burns so extreme care must be taken when handling these acids.
Disposal: Dispose of contents in an appropriate waste container.
References:
Newton, T.; Rothenberger, O.; Bunting, R. J. Chem. Educ. 1991, 68, 502.