acetyls alicylic acid (aspirin) synthesis

8/10/2019 Acetyls Alicylic Acid (Aspirin) Synthesis

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Acetylsalicylic Acid (Aspirin) Synthesis

Telow AJV

Sumicad, CJ, Tavanlar, EMMT, Chem 4!", #nstitute o$ Chemistry, %niversity o$

the &hilippines 'os aos

#! #ntroduction

*r+anic synthesis is the process where a desired or+anic compound is

constructed or prepared $rom commercially availale materials! The o-ective o$

or+anic synthesis is to desi+n the simplest synthetic routes to a molecule!

Aspirin, also .nown as acetylsalicylic acid is assalicylate dru+o$ten used

as anal+esic to relieve minor aches and pains, as an antipyretic to reduce $ever,and as an anti/in0ammatory medication! The history o$ aspirin and its medical

use can e traced way ac. in the second millennium CE! Medicines $rom

willow and other salicylate/rich plants appear in the E+yptian pharmacolo+y

papyri! 1urin+ 4 CE in 2reece, 3ippocrates +ives women willow tree lea$ to

relieve the pain o$ childirth! 3e also used salicylic tea to reduce $evers! illow

ar. e5tract then ecame .nown $or its e6ectiveness in reducin+ $ever, pain and

in0ammation in the mid/ ei+hteenth century! y nineteenth century, pharmacists

were e5perimentin+ with and prescriin+ a variety o$ chemicals related to

salicylic acid, an active component o$ willow e5tract!

#n "789, chemist Charles :r;d;ric 2erhardt treated acetyl chloride with

sodium salicylate to produce acetylsalicylic acid $or the s chemical structure and devised more e6icient methods o$ synthesis!

#n "7?@, scientists at the dru+ and dye


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and remain stron+ in the twenty/


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###!Methodolo+y

A! Schematic 1ia+ram

" +ram salicylic acid in "8/m' Erlenmeyer 0as.

G 9/m' acetic anhydride

G " drop 78H phosphoric acid

/swirl

/ heat in steam ath $or "8 mins

G /m' d3*

G /m' ice cold 3*

/cool to IT

/place in an ice ath

/per$orm suction


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G ?8H ethanol dropwise

swirl until almost all dissolves

G cold d3* dropwise until almost all crystals appear

cool 0as. in a cool ath

suction


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/ warm the tue in water ath $or 8

mins!

/ e5amine mi5ture

Ieaction with :eCl9

pinch o$ the sample in test tue

G 9 drops !8H aDueous :eCl9

G "/m' d3*

/ e5amine mi5ture

1i6erentiation o$ the synthesiFed acetylsalycylic acid $rom commercially

availale aspirin

pinch o$ the sample test tue

G 8 drops 3* and iodine / e5amine

! Set/ups


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"8?LC and a

density o$

"!44+cm9

plenty o$ water

acetic

anhydride

Converts

salicylic acids

hydro5yl +roup

into an acetyl

+roup

a colorless

liDuid with a

density o$ "!7

+cm9

Corrosive and

0ammale

eep away

$rom heat!

ear +loves,

eye protection

and $ace

protection

phosphoric

acid

Serves as the

catalyst

a colorless

viscous liDuid

with a density

o$ "!77 +cm9

and a oilin+

point o$ "87LC

E5tremely

corrosive

Avoid direct

contact! ear

chemical

protective

clothin+

?8H ethanol %sed $or the

recrystalliFatio

n

a colorless

liDuid with a

meltin+ pointo$ ""4LC and a

density o$

@7?!.+m9

S.in and eyes

irritants! 'on+

term use canresult to

serious liver

dama+e

eep away

$rom heat!

ear +loves,eye protection

and $ace

protection

Mn*4 1i6erentiatin+

a+ent

a purple liDuid 3i+hly

e5plosive

when reacted

with

concentrated

sul$uric acid

#n case o$

contact,

immediately

0ush s.in with

plenty o$ water

$or at least "8minutes

:eCl9 :or the

characteriFatio

n o$ the

synthesiFed

aspirin and

commercial

aspirin

rown liDuid

with a molar

mass o$

"B!+mol, a

oilin+ point

o$ 9B LC and

a density o$

!?+m'

Corrosive,

to5ic and

acidic

:lush s.in with

water in case

o$ direct

contact

#V! 1ata


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Tale ""!! 1escription o$ rea+ents

SAM&'E 1ESCI#&T#*K

salicylic acid white, powder/li.e sustance

acetic anhydride clear liDuid with stron+ odor

phosphoric acid clear, colorless liDuid with stron+ odor

?8H ethanol clear, colorless liDuid with stron+ odor

Mn*4 purple liDuid

:eCl9 rown liDuid

#odine solution clear liDuid

Tale ""!9! &reparation o$ Aspirin

SAM&'E 1ESCI#&T#*K

Salicylic acid G acetic anhydride G

78H phosphoric acid

salicylic acid was dissolved

Mi5ture at room temperature crystals were $ormed

Mi5ture a$ter ice ath more crystals were $ormed

Suction :iltrationresidue


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ei+ht o$ watch +lass G


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V! Sample Calculations

"!+ SA ( " mol SA "97!"B +) ( " mol ASA" mol SA) ( "7!"+ " mol ASA) P

"!9+

9! m' AA ( "!7+ AA "m')( " mol AA "!""+)(" mol ASA " mol AA)

("7! "+ " mol ASA) P 8!@+

H yield P Actual yield Theoretical yield Q "H

P !@7+ "!9+ Q "H P BH

H recovery P Iecovery yield Actual yield Q "H

P !48@+ !@7+ Q "H P 8?H

V#! Iesults and 1iscussion

#n this e5ercise, the +oal was to produce acetylsalicylic acid

throu+h the or+anic synthesis $rom the reaction o$ salicylic acid to acetic

anhydride, the startin+ materials! #nstead o$ usin+ acetic acid, acetic anhydride

was used as solvent since the anhydride reactin+ with water to $orm acetic acid

tends to drive the reaction to the ri+ht! #t results $rom the elimination o$ a

molecule o$ water $rom two molecules o$ acetic acid (see :i+! ""!)! :i+ure ""!9

elow shows the alanced chemical reaction o$ the synthesis o$ acetylsalicylic

acid!

:i+ure ""!! Structure o$ Acetic Anhydride


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:i+ure ""!9! The alanced chemical reaction o$ the $ormation o$

aspirin!

ecause the reaction is slow in pure acetic anhydride, the catalyst,

commonly stron+ acids li.e phosphoric acid was used $or the reaction!

Accordin+ to 'e Chateliers principle, the presence o$ e5cess acetic anhydride

$orces the eDuilirium towards the desired product, which in this case is the

aspirin! #n addition to this, the catalysts were also used to ensure that sidereactions, which may cause the percenta+e yield to increase, will e avoided!

The reaction ehind the synthesis is nucleophilic acyl sustitution!

Accordin+ to McMurry (), nucleophilic acyl sustitution happens when the

initially $ormed intermediate e5pels one o$ the sustitutes ori+inally onded to

the caronyl caron leadin+ to the $ormation o$ a new caronyl compound! #n

this e5periment, the speci


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anhydride resultin+ to a tetrahedral intermediate! The hydro5yl +roup (/*3)

attached to the electrophilic caron removed the hydro+en as proton thus

donatin+ the electron to $orm a doule ond (CP*)!The loss o$ the proton

re+enerates the phosphoric acid and thus, producin+ acetylsalicylic acid!

To enhance the synthesis reaction, addition o$ heat and water a$ter

heatin+ were done! The synthesis o$ reaction is $avored y heatin+ the mi5ture

ecause it speeds up the dissolution process o$ salicylic acid and increases its

soluility as well! ecause this speci


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Since the phenol +roup is asent in the synthesiFed aspirin, a ne+ative result

should e otained!

Another test was conducted to di6erentiate the synthesiFed aspirin $rom

the commercially/availale aspirin! :or the iodine test, the positive result is the

solution turnin+ lue or violet ecause o$ the presence o$ starch! #n this

particular e5periment, it is the commercially/availale aspirin that has a colorchan+e which is the solution e5hiited a $aint violet color! Theoretically, this

holds true ecause pharmaceutical companies add starch to talet medicines to

+ive them its characteristic shapes!

'astly, the meltin+ point determination was conducted! *ne way o$

identi$yin+ a sustance is throu+h its meltin+ point! The ran+e o$ the meltin+

point can +ive one an idea on the purity o$ the sample! The theoretical meltin+

point ran+e o$ aspirin is "7/"9@LC! #n this e5periment, the otained meltin+

point ran+e o$ o$ the crude aspirin is "B/ ""LC and $or the recrystalliFed

aspirin, it is ""4/""7LC! The result o$ meltin+ point determination means that

the samples have impurities in it! Karrow di6erence in the meltin+ point ran+eo$ the sample and the theoretical meltin+ point ran+e means that the sustance

is pure ecause o$ the uni$orm $orces present in the molecules! hen the ran+e

is wide, it means that the sample contains impurities! #n this e5ercise, meltin+

point determination is done! And the results show that it has a wide di6erence

$rom the theoretical meltin+ point ran+e o$ aspirin! Thus it can e in$erred $rom

the results that the sample is not pure!

V##! Summary and Conclusion

Synthesis o$ or+anic compounds involves +uidelines and steps that shoulde $ollowed! The


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starch in it! %n$ortunately, :eCl9, did not +ive the theoretical results!

V###! Ie$erences Aspirin timeline! ("9)! Ietrieved on *ctoer 8, "9 $rom

httpwww!tele+raph!co!u.healthhealthnews7"78"B4Aspirin/timeline!html

3istory o$ Aspirin! ("9)! Ietrieved on *ctoer 8, "9 $rom

httpen!wi.ipedia!or+wi.i3istoryo$aspirin

#nstitute o$ Chemistry! (")! asic *r+anic Chemistry 'aoratory

Manual! %niversity o$ the &hilippines 'os aos Colle+e 'a+una! @/@8!

Material sa$ety data sheet! ("9)! Ietrieved on *ctoer B, "9 $romhttpwww!inchem!com!phproductpa+es$ecl9msds!pd$

McMurry, John! ()! *r+anic Chemistry! @thEdition %SA!

MS1S $or potassium perman+anate! ("9)! Ietrieved on *ctoer B, "9

$rom httpwww!sciencela!commsds#dP??@4B

&hosphoric acid! ("9) retrieved on *ctoer B, "9 $rom

httpwww!ccohs!caoshanswerschemicalschempro

acetyls alicylic acid (aspirin) synthesis

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