Organic Synthesis of Aspirin Chemistry Formal Lab Sample Essay


The intent of this experiment is to synthesise a common organic merchandise called acetylsalicylic acid ( acetylsalicylic acid ) . and to go familiar with the optimal conditions needed for successful outputs. Aspirin is produced from an acid catalyzed reaction between salicylic acid with acetic anhydride. The crystalline acetylsalicylic acid is synthesized and purified by recrystallization. although there is non a 100 per centum output due to beginnings of mistake.


Aspirin is a medical specialty normally found in families around the universe. It besides is one of the least expensive and most utile drugs in the market. A Chemist named Felix Hoffmann foremost synthesized acetylsalicylic acid. otherwise known as acetylsalicylic acid. in 1897 from salicylic acid. 1

Salicylic acid is a of course formed substance. For illustration. willow trees have been recognized since antediluvian times as a natural beginning. Salicylic acid is found chiefly in the willow’s leaves and bark. The pure acid possesses several utile medicative belongingss. It is an antipyretic ( a febrility reducing agent ) . an analgetic ( a hurting reducing agent ) . and an anti-inflammatory ( a swelling reducing agent ) .

Unfortunately. pure salicylic acid makes for a peculiarly unpleasant medical specialty. The salicylic acid molecule contains two acidic functional groups. the phenol group and the carboxylic acid group. These groups make salicylic acid irritating because it burns the sensitive liners of the oral cavity. pharynx. gorge. and tummy.

These rough qualities are alleviated by replacing the acidic Hs with less reactive groups of atoms: the ethanoyl group group ( COCH3 ) . This consequences in acetylsalicylic acid or “aspirin” .

Acetylsalicylic acid is synthesized in labs and does non happen of course. It is produced from adding acetic anhydride to salicylic acid in the presence of sulphuric acid ( H2SO4 ) . an acerb accelerator: ( Diagram from 1 )

The drosss left over ( unreacted salicylic acid. acetic acid and sulphuric acid ) are removed by the procedure of recrystallization. This procedure separates pure acetylsalicylic acid by precipitating it out of the impure solution.

Pure acetylsalicylic acid contains merely one acidic functional group which bypasses most of the digestive system without doing Burnss. 2 Ultimately. acetylsalicylic acid hydrolyses with H2O. chiefly in the blood stream. to renew salicylic acid: ( Diagram from 1 )

There are four mathematical computations given by the teacher. They are:

1. Density = Mass / Volume

2. # of moles of the confining reagent = Weight of the confining reagent ( gms ) / Molecular weight restricting reagent ( grams/mole )

3. Theoretical Yield = # of moles of restricting reagent Ten

Of aspirinMolecular weight of acetylsalicylic acid ( Acetylsalicylic Acid )

4. Percentage existent Yield = ( Actual yield / Theoretical Yield ) X 100 %


Chemicals Used:

*Salicylic Acid: C7H6O3 ( S ) ( Provided )

*Acetic Anhydride: CH3COOCOCH3 ( cubic decimeter ) ( Provided )

*Sulfuric Acid: Conc. H2SO4 ( cubic decimeter ) ( Provided )

*Ethanol: C2H5OH ( cubic decimeter ) ( Provided )

*Acetic Acid: C2H4O2 ( cubic decimeter ) ( Prepared )

*Acetylsalicylic Acid: C9H8O4 ( S ) ( Prepared )


Followed the processs listed in the University of Winnipeg. Department of Chemistry Laboratory Manual. page 43.



PropertyMeasurement Method of Determination

Mass of salicylic acid1. 498 gAnalytical Balance

Volume of acetic anhydride5. 0 mLGlass Graduated Cylinder

Density of acetic anhydride1. 08 g/mLGiven by Lab Manual ( page 45 )

Weight of acetic anhydride5. 4 gSee # 1 in Calculations below

Molecular weight of salicylic acid138. 12 g/molGiven by Lab Manual ( page 45 )

Molecular weight of acetic anhydride102. 09 g/molGiven by Lab Manual ( page 45 )

Molecular weight of acetylsalicylic acid180. 16 g/molSee # 2 in Calculations below

Mass of filter paper + aspirin2. 103 gAnalytical Balance

Mass of filter paper0. 962 gAnalytical Balance

Mass of aspirin1. 141 gSee # 3 in Calculations below

Percent output of aspirin58. 42 % See # 4 in Calculations below


# 1 ) Density = Mass/Volume

Mass ( of acetic anhydride ) = Density X Volume

= 5. 0mL Ten 1. 08 g/mL

Mass ( of acetic anhydride ) = 5. 4 g

# 2 ) Molecular weight of

acetylsalicylic acid ( C9H8O4 ( S ) ) = molecular weight of its constituents.

=molecular weight of 9 ( C ) +8 ( H ) +4 ( O )

= 9 ( 12. 01g/mol ) + 8 ( 1. 00g/mol ) +

4 ( 16. 00g/mol )

Molecular weight of

acetylsalicylic acid ( C9H8O4 ( S ) ) = 180. 16 g/mol

# 3 ) Mass of aspirin = ( Mass of filter paper + acetylsalicylic acid ) – Mass of filter paper

= ( 2. 103g ) – 0. 962g

Mass of aspirin = 1. 141 g

Calculations continued:

# 4 ) # of moles of the confining reagent = Weight of the confining reagent ( gms ) / Molecular weight restricting reagent ( grams/mole )

= weight of salicylic acid / molecular weight of salicylic acid

= 1. 498g / 138. 12g/mol

= 0. 01085 moles of salicylic acid

Theoretical Yield = # of moles of restricting reagent Ten

Of aspirin Molecular weight of acetylsalicylic acid ( Acetylsalicylic Acid )

= 0. 01085 mol X 180. 16 g/mol

= 1. 953 g

Percent existent output of aspirin = ( Actual output of aspirin/ Theoretical Yield of acetylsalicylic acid ) X 100 %

= ( 1. 141g/ 1. 953g ) X 100 %

Percent existent output of aspirin = 58. 41 %

# 5 ) # of moles of salicylic acid = 0. 01085 mol ( see Calculation # 4 above )

# of moles of acetic anhydride = weight of acetic anhydride / molecular weight of acetic anhydride

= 5. 4 g/ 102. 09 g/mol

=0. 052 mol

Since: 0. 052 mol & gt ; 0. 01085 mol

Therefore: # of moles of acetic anhydride & gt ; # of moles of salicylic acid


Lab Manual Questions ( page 44 )

1 ) The confining reagent is salicylic acid. From the reaction equation ( located in the Introduction of this study ) one mole of Salicylic acid reacts with one mole of acetic anhydride to organize merchandise. Since there are fewer moles of salicylic acid relative to acetic anhydride ( see Calculation # 5 above ) . the sum of merchandise that can be formed depends on the sum of Salicylic acid. doing it the restricting reagent.

The theoretical output is 1. 935g and the percent output of the acetylsalicylic acid is 58. 41 % . The computations for the theoretical output and the per centum output can be seen in the consequences subdivision above.

2 ) The acetylsalicylic acid is washed with cold H2O in order to maintain the acetylsalicylic in a solid ( precipitate ) signifier. Cold H2O would take down the kinetic energy of the molecules. decelerate down their vibrational motion. and let them to crystallise into a solid. This makes it easier for us to filtrate and roll up the acetylsalicylic acid solid. Warm H2O would increase the kinetic energy of the acetylsalicylic acid molecules. increase their vibrational velocity. and interrupt their crystal constructions. This would fade out the acetylsalicylic acid into solution and do it much more hard for us to roll up and mensurate the acetylsalicylic acid.

Although acetylsalicylic acid was obtained utilizing recrystallization. the per centum output ( 58. 41 % ) was low. This due to the many beginnings of mistake nowadays in the lab. For illustration. residuary sums of acetylsalicylic acid were left over on many of the equipment used. particularly on stir rods and the interior of flasks. Even with distilled H2O. the acetylsalicylic acid was hard to take from the filter paper and glass surfaces in stairss three to five in the research lab manual3 ( Page 44 ) . Some of it was left over on the paper and glass surfaces. A solution for this is taking more attention when reassigning the merchandise from the different surfaces. Another solution is that in measure 5 of the lab3 ( page 44 1 could seek to rinse down the acetylsalicylic acid with four little 5mL parts of H2O instead than two big 10 mL parts as stated in the lab manual.

Another beginning of mistake is non leting adequate clip for the acetylsalicylic acid to recrystallize and precipitate in the ice bath. This would intend that some of the acetylsalicylic acid would be dissolved in solution and non be caught by the filter. A simple solution to this is leting the acetylsalicylic acid to recrystallize for a longer period without perturbation. One could besides add more ice to the ice bath which would chill the solution further and let precipitate to organize faster.

An extra beginning of mistake can happen during the drying of the filter paper in measure 5 of the lab manual3 ( page 44 ) . If one does non dry the paper plenty. so the residuary wet on the filter paper could do the weight measurings inaccurate. This can be solved by heating the filter paper for a longer period of clip.

Human mistakes. such as inaccurate measurings due to carelessness could besides impact the consequences. The obvious redress to this job is to pay attending and seek to make the lab work exactly.


Aspirin. besides known as acetylsalicylic acid. is derived from an acid catalyzed reaction between salicylic acid and acetic anhydride. This rough merchandise has drosss such as unreacted salicylic acid. acetic acid. and sulphuric acid that need to be separated from the pure acetylsalicylic acid. Recrystallization is a procedure which allows pure acetylsalicylic acid to precipitate out of this rough merchandise. In ideal fortunes. the theoretical output should be 1. 935 gms of acetylsalicylic acid. Yet the existent output was merely 1. 141 gms of acetylsalicylic acid. This gives a low per centum output of merely 58. 41 % . Although the method used in the lab works. it is in inefficient procedure of bring forthing pure acetylsalicylic acid. This is due most likely to the many mistakes. most of which are solvable. that can happen during the processs.


1Shusterman. Alan. Reed College Laboratory Reference. November 20. 2003. .

2Shlafer. Marshal. Ototoxic Drugs. November 20. 2003.

3The University of Winnipeg Department of Chemistry. Laboratory Manual of Introduction to the Chemical Properties of Matter 1111. 2003.


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