#15 Synthesis of Ethyl Salicylate from Salicylic Acid

#15 Synthesis of Ethyl Salicylate from Salicylic Acid
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Purpose: Salicylic acid is converted to the liquid ethyl salicylate by addition of ethanol.
Yields of salicylic acid (week 1) and ethyl salicylate will be found, as well as the overall yield of the 2-step conversion of acetyl salicylic acid to ethyl salicylate.
Introduction:
Esters are formed from the reaction of acids and alcohols: O O || || R-C-OH + HO-R’ → R-C-OR’ + H2O acid alcohol ester water
The pleasant smelling oil of ethyl salicylate is made by reacting salicylic acid (week 1) with excess ethanol. An acid catalyst is also needed. salicylic acid (SA) ethanol ethyl salicylate (ES)
The overall yield is determined from multiplying yields of the two reactions:
1. ASA + HCl(aq) →SA and 2. SA + ethanol → ES + water
Apparatus
The reaction takes place by refluxing (gentle boiling) in a 100-mL round bottom flask. This time the ice-cooled condenser is essential, otherwise the ethanol reactant (b.p.79˚C) would evaporate before the reaction was over.
Melting points of acetyl salicylic acid and salicylic acid (dried from week 1) are taken with MelTemp devices.
If you have never used one your instructor will demonstrate. MelTemp
C
OH
O
OH H OC H2CH3
H
+
C
OH
O
+ OCH2CH3
+ H2O2
Procedure
Part A: Esterification of Salicylic Acid with Ethanol
1. Before starting remove a spatulaful (that will be < 0.1 g) of SA (salicylic acid) and place in a labeled plastic vial to use for melting points.
2. In a 100 mL round bottom flask, mix at least 5 g dry salicylic acid (0.043 mol) with 20 mL 100% ethanol. The salicylic acid should be weighed out to two decimal places and recorded on the data sheet. The alcohol is in excess. It can be poured from a