[Chemical Engineering Laboratory 1]
Preparation of Aspirin and Oil of Wintergreen Candidate’s Name
:
SAM KAR YEN
Student ID
:
SCM - 027837
Group Member’s Name
: NG LIANG AIK KOW JING YANG FONG KA W!I "AN "AN Y!N #ING #ING "AI "AI SIM Y!! #$!NDA COO M%N J!NG LIM SIN NI! "AN "AN WOAN WOAN GI%N $ONALD $ONA LD S!L& S!L&AM OLI&!$ '$ASA" '$ASA"
Le(turer) Super*isor
:
D$ WONG &OON LOONG
Date o+ Submission
:
,-t. MA$C /0,1
1. AB!"AC!
In this laboratory experiment, acetylsalicylic acid and methyl salicylate was synthesised. Acetylsalicylic acid is commonly known as aspirin while methyl salicylate as oil of wintergreen. To synthesis aspirin, acetic anhydride and five drops of concentrated sulphuric acid was added to salicylic acid. Sulphuric acid acts as a catalyst to increase the rate of reaction by lowering the activation energy. Suction filtration is performed to separate the residue. The residue was washed for several times as acetic anhydride is decomposed by the addition of water for the formation of aspirin. Formed aspirin is allowed to air dry. To synthesis oil of wintergreen, salicylic acid was mixed with methyl alcohol. Three drops of concentrated sulphuric acid was added as a catalyst to speed up the reaction. The odour released was noted before and after heating. Finally, both the products collected were tested with ! of iron "III# chloride, all the changes were recorded. Through this experiment, we can know that two different esters compound can be synthesised by the same chemical which is salicylic acid.
#. $%!"O&'C!$O%
$rganic compound synthesis and uses are very important section is this modern world. Acetylsalicylic acid and methyl salicylate are bo th an ester. An ester compound can be formed by reaction of a carboxylic acid "compound containing %&$$' group# and an alcohol "compound containing an %$' group#. The reaction is termed as esterification. (sters basically have strong and pleasant scents, such as odour of strawberries and mint. In this way, many esters will be used as flavourings and perfume agents, as well as ointments for the relief of muscle pain.
#.1 Acetylsalicylic acid
Acetylsalicylic acid also known as aspirin, has the potentiality as an analgesic to reduce minor pains, as an anti)inflammatory medication to reduce redness and as an antipyretic to reduce fever. Theoretically, aspirin can be synthesised by heating salicylic acid and acetic acid for a certain period of time. 'owever, to accomplish the esterification more *uickly, acetic anhydride was used instead of acetic acid in this experiment. It is because acetic anhydride is more reactive. O
+
O H+
O
O
HO
O
OH
+
OH
O O
OH
O
Sa2i(32i( a(id
A(eti( an.3dride A(et32sa2i(32i( a(id a(id
A(eti( a(id
#.# (ethyl salicylate
+ethyl salicylate has a common name as oil of wintergreen. +ethyl salicylate will release a pleasant minty scents. +ethyl salicylate is used as a flavouring agent and the in rubbing liniments that can relief the muscle cramping because it can penetrate through skin. It is prepared by esterification of the carboxylic acid group ")&$$'#, of salicylic acid with methyl alcohol. H+
+ OH
+
OH HO
OH
O
Sa2i(32i( a(id
H2O
O O
Met.32 a2(o.o2
Met.32 sa2i(32ate
henol is a compound in which the hydroxyl group ")$'# attached to a phenyl ring ")& -'#. This compound presents in both salicylic acid and methyl salicylate but not in acetylsalicylic acid. +ost of the phenols will form coloured complexes with iron "III# chloride, Fe&l /. Thus, ! Fe&l/ solution is added to test for the presence of phenol. The colours range from green through blue and red through violet.
). E*perimental (ethod
).1 Ob+ecti,es • • •
To synthesis acetylsalicylic acid To synthesis methyl salicylate To review the phenol function group reacts with iron"III# chloride.
).# Apparat-s • • • • • •
0ml (rlenmeyer Flask 1ml graduated cylinder Filter paper -11ml beaker 2arge test tube 3ater bath
).) Chemical • • • • • • • •
Acetic anhydride ! iron"III# chloride solution, Fe&l/ Salicylic acid Ice Absolute ethanol +ethyl alcohol &oncentrated sulphuric acid, '0S$4 5istilled water
). Ca-tions •
If acetic anhydride and concentrated '0S$4 come in contact with skin, can cause severe burns. Immediately wash the area with large amount of water if you get any of these
•
reagents on you. Instead of disposing any chemicals down the sink, use the waste containers provided.
)./ Proced-re
"i# Synthesis of Aspirin
Add /g of salicylic acid in a 0ml (rlenmeyer flask
Add -ml of acetic anhydride and drops of concentrated '0S$4
+ix the reagent by swirling the flask
lace the flask in 61o& of water bath for 01 minutes
&ool down to room temperature
Add 41ml of distilled water to the mixture.
&ool the mixture in ice bath
Filter the crystals and wash with water
Allow the crystal to air dry
$btain and record the mass of crystal.
"ii# Synthesis of $il of 3intergreen
lace g of salicylic acid and ml of methyl alcohol in large test tube
Add / drops of concentrated '0S$4
lace the test tube in 71o& of water bath for minutes
8ote the odour
Add a drop of ! Fe&l/
8ote the colour changes
. "es-lts and Analysis
"i# Synthesis of Aspirin •
+ass of salicylic acid 9 /.11 g
•
+ass of crystalli:ed aspirin
9 Total mass of crystalli:ed aspirin ) mass of filter paper 9 /.g % 1.7 g 9 0./- g The total mass of crystalli:ed aspirin was weighed 0./g, but to get the mass of dry crystalli:ed aspirin, the aspirin was left for two days from the experiment da y to air dry. The mass of dried aspirin weighed /.g and the mass of filter paper is 1.7g. •
+oles of salicylic acid used "mol wt of salicylic acid9/6amu# 1 mol × 2.36 g 0,02 mol 9 138 g g " amu 9 # mol =
•
Theoretical number of moles of aspirin 9 +oles of salicylic acid used 91.10 mol
•
Theoretical grams of aspirin "mol wt of aspirin 9 61 amu# 180 g × 0.02 mol 9 mol 9 /.-1 g
•
ercent yield grams aspirin obtained × 100 9 theoretical grams aspirin 2.36 g × 100 9 3.60 g 9 -.- !
3hen Fe&l/ was added to salicylic acid, the colour changed from white to purple colour. Then it slightly changed to brownish colour after few seconds.
3hen Fecl/ was added to aspirin, the colour changed from very light pink to purple colour. Then part of it changed to brownish colour after few seconds.
3hen Fecl/ was added to recrystalli:ed aspirin, the colour changed from light pink to purple.
"ii# Synthesis of $il of 3intergreen +ethyl salicylate releases a pleasant minty odour. 3hen Fe&l/ was added to the product, a change of colour is observed from colourless to purple colour.
/.0 &isc-ssion
"i# Synthesis of acetylsalicylic acid O
OH
+
O H+
O
HO
O O
OH
+ O
O OH
O
Sa2i(32i( a(id
A(eti( an.3dride A(et32sa2i(32i( a(id a(id
A(eti( a(id
Acetylsalicylic acid is also well known as aspirin. To obtain the percentage yield, divide mass of aspirin obtained with theoretical mass of aspirin. Theoretically, number of moles
of aspirin is e*ual to number of moles of salicylic acid used. It is because according to the e*uation above, ratio of salicylic acid used and aspirin formed is ;mol in the process of esterification.
'0S$4 acts as a catalyst in this experiment. '0S$4 will not increase the aspirin obtained but will lower the activation energy to formed a product, so that the rate of reaction is faster. 'owever, to accomplish the esterification more *uickly, acetic anhydride was used instead of acetic acid in this experiment. It is because acetic anhydride is more reactive.
The suction filtration process in this experiment is to separate the residue which is unreacted salicylic acid and acetic anhydride. The residue was washed for several times as acetic anhydride is decomposed b y the addition of water for the formation of aspirin. To obtain the mass of aspirin without the water content, the product formed is allowed to air dry.
&old as opposed to warm water was used to wash the aspirin that prepared because aspirin is more soluble in warm water. &old water would not dissolve as much as warm water do. As the temperature lowers, more precipitates is gained, this minimi:es the product loss. The crystal can only be caught by the filter paper, if the aspirin dissolves in warm water, a bad yield will be gained.
There is a colour change from white to purple colour when ! of Fe&l/ is added to the salicylic acid because of the presence of phenol ring in it. 3hen ! of Fe&l/ is added to the aspirin obtained, the colour changed from light pink to purple because it was impure. 'owever, no changes of colour will occur when F e&l/ were added to pure aspirin because the phenolic ")$'# of salicylic acid is protected by the acetate group ")$$&) &'/#.
If the experimental yield of aspirin obtained is greater than 11!, means the aspirin is not completely dry, there is still water content in the aspirin. Thus, the mass of aspirin recorded is higher than the mass of the theoretically aspirin.
"ii# Synthesis of +ethyl salicylate The reaction occurred between salicylic acid and methyl alcohol is also known as esterification. The concentrated '0S$4 added in the reaction acts as a catalyst to overcome the activation energy to form methyl salicylate.
+ethyl salicylate has a common name which is $il of 3intergreen. From the common name, can know that methyl salicylate will release a pleasant minty odour. The minty odour released is because esters basically will release strong and p leasant odour.
3hen Fe&l/ is added to oil of wintergreen, the colour changed from colourless to purple colour. It is because the phenol group in it.
.0 Concl-sion
In this experiment, both the synthesised product is formed b y the common chemical which is salicylic acid undergoes the process of esterification.
2.0 "eferences
•
Acetylsalicylic Acid "Aspirin# Synthesis, online, retrieved on =th +arch 01, from
•
http;>>www.academia.edu>4706==->Acetylsalicylic?Acid?Aspirin?Synthesis Synthesis of Aspirin and $il of 3intergreen, online, retrieved on =th +arch 01, from https;>>www.apsu.edu>sites>apsu.edu>files>chemistry>S?10?Synthesis?of?Aspirin?a
•
nd?$il?of?3intergreen.pdf (xperiment ; reparation of aspirin and $il of 3intergreen from 2aboratory 'andbook
