How To Find Theoretical Yield Of Aspirin

Introduction

Aspirin, chemically known as acetylsalicylic acid, is an over-counter pharmaceutical drug commonly used to reduce hurting and inflammation. Salicylic acrid, in which aspirin is organically derived from, is bitter and irritable to the stomach, so in club to form the drug, salicylic acid and acetic anhydride must be reacted in the presence of an acid based goad. Nonetheless, this reaction is tiresome and has a relatively low yield. If acetic anhydride is used instead of acetic acid, the reaction is much faster and has a college yield. "Acetylsalicylic acid does not have the bad taste and tummy bug of salicylic acid. Once acetylsalicylic acrid is absorbed from the intestine, it is converted back to salicylic acid" (CHEM 322, 2013). It is an aromatic compound containing both a carboxylic acid and ester functional group. German chemist Felix Hoffman was the first to experiment in the synthesizing of aspirin and was credited with the success of the revolutionary drug. The experiment conducted in this report will synthesize, purify and determine the percentage yield of aspirin. The purity of the product formed will then be determined by a series of tests. Iron (lll) Chloride testing, melting signal range and Thin Layer Chromatography tests will all be conducted.

Effigy one: Reaction produced in the forming of Aspirin.

Figure 2: Compound structure of Aspirin containing carboxylic acrid and ester functional groups.

Equilibrium of Aspirin

The state in which the rate of the forward reaction equals the rate of the astern reaction can be divers equally chemic equilibrium. This also ways that no net change in concentrations of reactants and products. Many factors influence the country of equilibrium. Increasing the temperature will shift the equilibrium towards the endothermic reaction, whereas decreasing the temperature will shift in the direction of the exothermic reaction. As well as temperature, a goad tin change the mechanisms of a reaction by lowering the activation free energy as for both the forward and backward reaction.

Effigy 3: Equilibrium Graphed

Le Chatelier's principle and esterification of the phenolic hydroxyl group of salicylic acid will be used to synthesize aspirin within this reaction. Le Chatelier'due south principle states that if a constant, in this case a catalyst, is applied to a system in equilibrium, "the equilibrium will shift and then every bit to tend to annul the effect of the constraint." (Linfield, 2015). The reaction that is used for the synthesis of aspirin shown below (Figure four) uses an excess of acerb anhydride, sulfuric acid as a catalyst, and heat to push the equilibrium toward the products.

Figure 4: Equilibrium of Aspirin

Ferric Iron (lll) Chloride Test

Salicylic acid contains a phenol group, and phenols are known to be irritating to the tum, in the original synthesis of aspirin, The Bayer Company this phenol group with an ester. This esterified compound, which is acetylsalicylic acid, proved to be significantly less irritating than salicylic acrid. Inside the process of synthesizing aspirin, the phenol group on the salicylic acid forms an ester with the carboxyl grouping on the acetic acid, seen beneath in Effigy iv.

Figure 5: Carboxyl and Ester Groups forming.

Iron (lll) Chloride is known to react with phenol groups. A phenol group is distinguished as the -OH that is coming off a ring system. If iron chloride is added to a reactant containing a phenol group, the solution would plow purple. Aspirin does non incorporate a phenol grouping, nonetheless, salicylic acid, contains a phenol group. Therefore, fe chloride is added to aspirin samples to test for the presence of unreacted salicylic acid. If there is unreacted salicylic acid, the substance will turn a deep royal colour, if non the substance should show a yellow colour.

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Thin Layer Chromatography Test

Thin Layer Chromatography (TLC) is a common technique used in guild to separate a mixture of compounds, as well as identifying and determining the purity of a compound. Through capillary activeness, "compounds can split due to their different affinities for the mobile and stationary phases." (Mohrig, 2012).  The stationary stage in TLC tin be described equally the adsorbent, coated on a sheet of metal. It is usually silica or alumina. The mobile stage is the solvent which slowly rises because of the capillary action and polarity. The polarity of a chemical compound is determined past its functional groups and masses. Salicylic acid is more than polar than aspirin. Acetylsalicylic acid contains an ester and acetyl functional groups, therefore giving it a larger mass than salicylic acrid. Hydroxyl groups are more polar than acetyl groups, indicating that salicylic acid is more probable to absorb to the silica because of its hydrogen bonding. Furthermore, "the acetylsalicylic acid will exist in a free country and travel further considering the ester and acetyl functional groups no longer take hydrogen bonds that bond to the polar silica plate." (ChemGuide, 2016). If an aspirin sample is completely pure, only one spot volition be displayed on the TLC plate. The rough aspirin might have two different spots because it is not entirely pure. UV low-cal is used to visualize the compounds on the plate.

Reflux

Reflux condensing is the application of estrus to a reaction to overcome the issue of evaporating likewise much solvent and drying the reaction vessel. Reflux involves heating the chemical reaction for a specific corporeality of time, while continually cooling the vapor produced dorsum into liquid course, using a condenser. Because the vapors produced to a higher place the reaction continually undergo condensation, it guarantees that the temperature of the reaction remains constant.  Reactants for reflux experiments are usually both liquids, but tin be both solid and liquid. The temperature at which the reaction is heated depends on the boiling points. Whilst the reaction is taking place, the condenser is e'er completely filled with water to ensure efficient cooling. "The vapors, which are given off from the liquid reaction mixture, change from gas phase back to liquid phase due to estrus loss. This then causes the liquid mixture to fall dorsum into the circular bottom flask." (University of Birmingham, 2019).

Effigy half dozen: Reflux Condenser Setup

In a reflux reaction with aspirin, the best yield should exist obtained by heating the mixture of reactants effectually in a higher place the solvents humid betoken. This will let for optimal heat and higher rate of collisions during reaction, allowing more production to be produced. Notwithstanding if the reaction is heated at too higher temperature, the reflux can fail and gas can escape, causing loss of product.

Recrystallization

After the crude aspirin product is prepared, information technology is likely to be impure and needs to be purified by the process of recrystallization, the solvent used for this process is ethanol and water. In general, recrystallization is a process for purifying compounds. In order to recrystallized the crude product the solid must exist dissolved in an appropriate solvent at a high temperature.  If a solid production is dissolved in hot solvent first, crystals should form when the hot solution begins to cool. For case, an ice-water bath is often used to cool the solution. The solid should be recovered with greater efficiency at these temperatures, provided the solvent itself does not freeze.

Melting Point Test

The Carboxylic acid group in aspirin's structure allows molecules of aspirin to grade hydrogen bonds with each other. Because of the permanent dipole bonds within the aspirin molecule. Because of such a stiff attraction, it indicates that aspirin's melting signal is relatively high. However, the melting indicate of salicylic acid is expected to be college than the melting betoken of aspirin equally there are more hydrogen bonds formed which means that more than energy is needed to interruption the bonds. So when testing the purification of aspirin, pure salicylic acid's melting signal should be higher than the aspirin sample.

Enquiry Question:

What are the optimum weather for the manufacture of aspirin?

Aim:

To determine the effect of a catalyst and reflux methods on the synthesis of salicylic acid and acetic anhydride.

Hypothesis:

If the variables being tested alter the manufacture conditions, in which the aspirin can be synthesized then it can be proven that they significantly bear on the outcome, producing in pure aspirin.

Preliminary Experiment

Controlled Variables:

Goad: The purpose of a goad within a reaction is accelerate it. Too as speeding upward the reaction, it presents an alternative way for the reaction to occur, therefore lowering the activation free energy needed. Dissimilar other compounds within the mixture, a catalyst lasts the reaction without being changed. The 2 catalysts used in the following experiment are sulfuric acid and phosphoric acid.

Reflux and Non-Reflux: The aspirin sample being manufactured will be synthesized using 2 unlike methods, processed through a reflux condenser and then heated alone with a reflux condenser. The purpose of this is to examination whether refluxing the product has effect on its purity.

Method:

REACTION WITH REFLUX

1. 2g of 2-hydroxybenzoic acrid was weighed out and then transferred to the reflux flask.
2. 5ml of acetic anhydride was added to ensure that it would be present in backlog.
3. The flask was continuously swirled subsequently the addition of ethanoic anhydride.
4. A total of 8 drops of sulfuric acid (60% concentration) was added, the flask continued to be swirled subsequently each drib.
5. Once the mixture was cooled two anti-bumping granules were added to assist the mixture eddy smoothly.
6. The mixture was and so refluxed for twenty minutes.

Manufacture & PURIFICATION:

Used Method A:

1. 150mL of cold distilled water and 10mL of diluted sulfuric acid (2moL) were placed in a 250mL beaker.
2. Very slowly, the reaction mixture was poured into the water.
3. The mixture was stirred and left to stand up for roughly 15 minutes.  Both 2-hydroxybenzoic acid and aspirin are almost insoluble in acidic solution, and will separate equally fine white crystals.
4. The filter paper was cutting to shape to fit the Buchner funnel attached to the vacuum filtration equipment.
5. The scout drinking glass and filter paper were pre-weighed.
6. The crystals were rinsed out onto the filter paper and stale through the vacuum filtrations system.
7. The crystals were then warmed in an oven roughly set to 105^oC.
8. The mass of the raw product was so adamant.
9. Summate the % yield of raw product as a % of the mass of aspirin that was theoretically possible if all of the 2-hydroxybenzoic acid was converted to aspirin.

RECRYSTALLIZATION

1. The solid was transferred from the filter newspaper to a clean, dry 125ml conical flask.
2. The crude product was then dissolved in 5ml of warmed (via water bathroom) 100% ethanol.
3. If the crystals do non all dissolve, add 2 mL more than of the ethanol and continue to warm the mixture to deliquesce the crystals.
4. 50ml of warm water was added to the articulate booze solution, per 20ml. The flask connected to be heated in order to dissolve whatsoever forming crystals.  (17.5ml)
5. The flask was fix bated to cool, close fully observed.
6. Once the crystals had formed, the flask was cooled with common cold water. The crystals were then formed and the process went to completion.
7. Afterward 10 minutes of cooling, the beaker was placed in an water ice bathroom and crystals formed afterward 1 calendar week.
8. The filter newspaper was cutting to shape in order to fit the Buchner funnel.
9. The watch glass and filter paper were pre-weighed.
10. The crystals were scraped out on to the filter newspaper from the Buchner funnel to the watch glass, drying them through vacuum filtration.
11. The mass of the purified recrystallized product was determined and recorded.

Purification Test Results

Melting Point Examination:

Non-Reflux Sulfuric Acid

	Salicylic Acid	Shop Bought Aspirin	Own Sample
Trial ane	133oC	139oC	133oC
Trial ii	133oC	137oC	132oC

Reflux Sulfuric Acrid

	Salicylic Acid	Store Bought Aspirin	Own Sample
Trial ane	164oC	145oC	130oC
Trial 2	155oC	140oC	135oC

Not-Reflux Phosphoric Acid

	Salicylic Acid	Store Bought Aspirin	Ain Sample
Trial 1	146oC	142oC	130oC
Trial 2	144oC	138oC	144oC

Reflux Phosphoric Acid

	Salicylic Acrid	Store Bought Aspirin	Own Sample
Trial 1	145oC	140oC	138oC
Trial 2	149oC	142oC	146oC

Sparse Layer Chromatography Plate Test:

Non-Reflux Sulfuric Acrid Non-Reflux Phosphoric Acid

Trial 1                                                                                               Trial 1

Salicylic Acid

Store Bought Aspirin

Own Aspirin Sample

Salicylic Acid

Shop Bought Aspirin

Own Aspirin Sample

Reflux Sulfuric Acid

Trial 1

Salicylic Acid

Store Bought Aspirin

Own Aspirin Sample

Table ane: Synthesis of Aspirin Non-Reflux Sulfuric (Trial i)

Mass of Salicylic Acrid used (m)	2.00g
Book of Acerb Anhydride used (mL)	5.00mL
Mass of Filter Newspaper (g)	0.59g
Mass of Watch Glass (g)	34.93g
Mass of filter paper, watch glass and aspirin (g)	36.63g
Mass of aspirin synthesized (g)	1.11g

Table 2: Synthesis of Aspirin Not-Reflux Sulfuric (Trial 2)

Mass of Salicylic Acid used (g)	two.00g
Book of Acerb Anhydride used (mL)	5.00mL
Mass of Filter Newspaper (g)	0.61g
Mass of Sentry Drinking glass (g)	35.21g
Mass of filter paper, watch drinking glass and aspirin (g)	36.91g
Mass of aspirin synthesized (g)	ane.09g

Table 3: Synthesis of Aspirin Reflux Sulfuric (Trial i)

Mass of Salicylic Acid used (g)	2.00g
Volume of Acetic Anhydride used (mL)	5.00mL
Mass of Filter Newspaper (g)	0.58g
Mass of Watch Glass (yard)	94.17g
Mass of filter newspaper, watch glass and aspirin (m)	95.19g
Mass of aspirin synthesized (g)	0.44g

Table 4: Synthesis of Aspirin Reflux Sulfuric (Trial 2)

Mass of Salicylic Acid used (g)	2.00g
Book of Acetic Anhydride used (mL)	5.00mL
Mass of Filter Newspaper (chiliad)	0.62g
Mass of Watch Glass (1000)	37.98g
Mass of filter paper, lookout drinking glass and aspirin (1000)	39.12g
Mass of aspirin synthesized (yard)	0.52g

Table 5: Synthesis of Aspirin Non-Reflux Phosphoric (Trial 1)

Mass of Salicylic Acid used (k)	2.00g
Volume of Acerb Anhydride used (mL)	five.00mL
Mass of Filter Paper (1000)	0.56g
Mass of Watch Glass (grand)	82.59g
Mass of filter newspaper, watch glass and aspirin (g)	84.17g
Mass of aspirin synthesized (g)	1.02

Table half dozen: Synthesis of Aspirin Non-Reflux Phosphoric (Trial 2)

Mass of Salicylic Acid used (one thousand)	two.00g
Volume of Acetic Anhydride used (mL)	5.00mL
Mass of Filter Paper (g)	–
Mass of Watch Drinking glass (1000)	–
Mass of filter newspaper, lookout man glass and aspirin (g)	–
Mass of aspirin synthesized (thou)	–

Table 7: Synthesis of Aspirin Reflux Phosphoric (Trial 1)

Mass of Salicylic Acrid used (1000)	2.00g
Volume of Acerb Anhydride used (mL)	five.00mL
Mass of Filter Paper (g)	0.50g
Mass of Watch Drinking glass (1000)	82.01g
Mass of filter paper, spotter glass and aspirin (grand)	82.96
Mass of aspirin synthesized (1000)	0.45g

Table eight: Synthesis of Aspirin Reflux Phosphoric (Trial two)

Mass of Salicylic Acid used (g)	two.00g
Volume of Acerb Anhydride used (mL)	5.00mL
Mass of Filter Paper (g)	0.59g
Mass of Watch Glass (g)	81.88g
Mass of filter paper, lookout man glass and aspirin (thousand)	84.40g
Mass of aspirin synthesized (g)	0.93g

Assay and Give-and-take

The initial reaction and formation of the product produced excessive samples both raw and pure aspirin. The 'raw' sample, withal, seemed to retain more water than the other sample and held a tackier texture. Through recrystallization of the aspirin, the pure sample turned out more like powder and much purer white in color. In one case the samples were made, the tests to analyze them began. Commencement, was the atomic number 26 (III) chloride exam in which each sample was combined with the iron solution to observe the color produced. The presence of salicylic acid creates a night purple colour, varying from sample to sample based on the amount independent. The raw and recrystallized samples both produce a relatively nighttime purple colour, very different from the burnt orange colors of the store bought aspirins. The raw should accept contained amounts of salicylic acid inside the sample, although the recrystallized sample should have contained a smaller amount. This could have been due to a faulty recrystallization and/or the contamination of the samples. A vacuum filtration was used to filter out the crystals from the solution, which could have not completely filtered correctly. If the process was rushed, and the crystals were not allow to dry out long enough, the samples may take retained any bit of water and/or salicylic acrid. Still, pure synthesized samples produced slightly lighter regal colours, indicating the presence of salicylic acid. This proves a trouble as the samples synthesized through the experiment should be pure. Whilst it is understandable that the raw sample holds hints of salicylic acrid, the pure aspirin should take extracted the traces through the recrystallization process. This indicates the synthesized samples held a low percentage purity.

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When observing the given TLC plate however, the salicylic acid column contains a large spot that has travelled upwards. Suggesting the salicylic acrid was completely dissolved into the sample, allowing the sample to run to the finish of the plate. Even so when comparison it against the shop bought aspirin, the store bought aspirin had a stronger presence. This shows that at that place was very few traces of salicylic acrid within the shop bought aspirin, beingness the most pure out of the 3 samples. In regards to the experimentally synthesized aspirin, the marks on the TLC plate fluctuate proving a presence of salicylic acid in the recrystallized samples. Finally, the melting point test proved that the synthesized samples, salicylic acid and store bought aspirin were accurate. Each sample melting under the estrus fell inside the normal ranges of each sample. While the melting point examination proved to be the most accurate, the consistency of the other tests proved unreliable, questioning the purity of the sample synthesized.

Sample Calculations:

References

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