Transcript Slide 1

Experimental Reports
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Next week is the final week of practicals
Make sure you are up to date with your
reports by next week – all reports
Final reports must be handed up no later
than one week after completion of final
practical – otherwise marks will be forfeited
Experiment 17
Reactions of Alcohols and
Carboxylic Acids
Introduction
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Given samples of various alcohols and
carboxylic acids
Establish some of their physical and chemical
properties & perform various reactions
HO
HO
ethanol
HO
pentanol
benzyl alcohol
O
HO
O
ethanoic acid
OH
propanoic acid
Introduction
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You will perform solubility and acidity
tests on all the compounds provided
Ester formation from an alcohol and
carboxylic acid
Oxidation of an alcohol to a carboxylic
acid using permanganate solution
Solubility Tests
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To 1ml of water in three test tubes, add
each of the alcohols dropwise until they
cease to dissolve or until 10 drops have
been added
Record your observations
Repeat with the two carboxylic acids
Comment on your conclusions regarding
the solubilities in water
Acidity Tests
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Use the aqueous solutions of ethanol
and ethanoic acid from the solubility
tests
Test both with blue litmus paper
Add 1ml of 10% NaHCO3 to each
Record your observations in each case
Acidity Tests
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Dissolve 0.5g of sodium acetate in 5ml
water – note if there is any odour
Add 1ml dilute H2SO4 and again note if
there is any odour
Record your observations in each test
and explain any reactions observed
Ester Formation
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Already encountered in Experiment 14
Heat 2ml of ethanol, 1ml ethanoic acid and a
few drops of conc H2SO4 for 5 mins
Note any changes you observe – odour?
O
O
OH
ethanol
+
H+
HO
ethanoic acid
O
ethyl acetate
Ester Formation - Mechanism
H+
H
O
OH
O
HO
HO
Include mechanism
for ester formation
in your report
HO
O
HO
H+
OH2
O
-H2O
O
-H+
HO
O
Oxidation of Phenylmethanol
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Phenylmethanol (benzyl alcohol) can be
oxidized to give benzoic acid
To 1ml of phenylmethanol in a conical
flask add 25ml of KMnO4 solution and
0.5g of sodium carbonate
Heat on the water bath for 20 mins
Cool & acidify with conc HCl
Oxidation of Phenylmethanol
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Add sodium sulphite solution until the
brown maganese dioxide dissolves
Cool to room temperature – white
precipitate of benzoic acid settles out
HO
HO
KMnO4
O
benzyl alcohol
benzoic acid
Oxidation of Phenylmethanol
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Isolate crystals on the Hirsch funnel,
wash with water & dry
Get melting point when dry
Calculate % yield from number of moles
of phenylmethanol you began with
Calculations
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Density of phenylmethanol = 1.05 gml-1
Use the density & volume to calculate
the mass of phenylmethanol used
m

V
m   .V
m
n
MR
Calculations
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Use the mass of phenylmethanol to
calculate the number of moles
When dry, weigh the benzoic acid
product and thus calculate the number
of moles of product
% yield = moles benzoic acid/moles
phenylmethanol
Report
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Introduction
All observations from the solubility and
acidity tests & reactions
Mechanism for ester formation
Weight and melting point
% yield of benzoic acid
Discussion & conclusions