Lab 2 a - This is a lab report for experiment 2 PDF

Preview

Summary

This is a lab report for experiment 2...

Description

SEPARATING THE COMPONENTS OF PANACETIN HINA WAZIRI CHEM C343 DAN GODFREY LAB REPORT 2 : 14 FEB 2018

Lab 2: Separating the Components of Panacetin Introduction

The purpose of this lab is to separate the components of panacetin and later determine the identity of the unknown compound. The components of panacetin in this experiment to be tested are sucrose, aspirin and the unknown. The experiment was conducted to test the hypothesis that percent composition of each components in Panacetin is accurate and to conclude the ‘label is accurate’.

Panacetin is both an analgesic drug and an antipyretic drug. Analgesic drugs reduce pain while antipyretic drugs reduce fever. The Panacetin used in this lab is made up of aspirin, sucrose, and an unknown compound that may either be acetanilide or phenacetin. Aspirin is an analgesic and an antipyretic. Acetanilide and phenacetin are both pain killers and Sucrose is a simple sugar that is an inactive ingredient in this medication. Using techniques such as extraction, evaporation, and filtration, the three components will be isolated based on their solubilities and acid-base properties.

Mixing the Panacetin with dichloromethane will dissolve away the aspirin and the unknown substance, leaving just the sucrose behind and can be separated using gravity filtration. Sucrose is insoluble in dichloromethane and is left behind as the residue and the filtrate is the aspirin and the unknown. Aspirin can be removed from the dichloromethane solution by extraction in a separatory funnel with an aqueous solution of sodium hydroxide. It forms two layers the aqueous and the organic layer. The aspirin can be separated using vacuum filtration. Finally, evaporating the solvent from the dichloromethane can isolate the unknown component.

Reaction Mechanism/Discussion

Separation of Sucrose: 3.01 grams of panacetin was mixed with 50 ml of dichloromethane. The mixture was stirred to dissolve as much of the solid as possible and then the sucrose was separated by gravity filtration. The residue was collected and left to dry for the next lab period. After drying the residue was weighed and mass of sucrose recorded to be 0.28grams. The observations seen can be explained by the fact that sucrose is insoluble in organic solvent such as dichloromethane.

Separation of Aspirin: The filtrate obtained was transferred to a separatory funnel and extracted with sodium hydroxide. 2.25 grams of sodium hydroxide pellets were used to prepare a mixture of 50ml NaOH. Two layers were seen the top layer being the aqueous layer and the bottom layer the organic layer. After the layers separated, the dichloromethane layer was placed into another container, then returned to the separatory funnel to repeat the process. 7.0 mL of 6M hydrochloric acid was combined with the aqueous extracts obtained from the previous step. The pH was tested to be less than 2. The mixture was then cooled in an ice bath for ten minutes. Vacuum filtration was used to collect the aspirin which was washed with cold water then left to dry for a week for the next lab period. After drying mass of the aspirin was weighed and recorded to be 0.9grams.

Aspirin, acetanilide and phenacetin are soluble in dichloromethane but relatively insoluble in water. Aspirin reacts with bases such as sodium hydroxide to form a salt sodium acetylsalicylate which is insoluble in dichloromethane and soluble in water. This salt thus migrates from the dichloromethane layer to the aqueous layer. Acetanilide and phenacetin are not converted to salts by sodium hydroxide thus the unknown stays in the dichloromethane layer as the organic layer.

To recover the aspirin from the precipitate HCl was added to the solution until the pH reached approximately 2. A low pH indicated that the entire amount of the sodium acetylsalicylate reacted with the acid to produce aspirin. H+ is excess in the reaction.

Isolation of the unknown component: Evaporation technique was used to evaporate the solvent from the dichloromethane solution (organic layer collected). The evaporation was discontinued when only a solid residue remained in the flask. The unknown was transferred to a watch glass and weighed to be 1.10 grams

Data collected was recorded as in Table 1 below:

Table 1

Mass of panacetin used

3.01 grams

Mass of sucrose

0.28 grams

Mass of aspirin

0.9 grams

Mass of the unknown

1.10 grams

Percent recovery

75.7 %

Percent composition of sucrose

12.28 %

Percent composition of aspirin

39.5 %

Percent composition of the unknown

48.24 %

According to the data the percent composition for each of the components fall within the accepted ranges of 8-12% sucrose, 35-45% aspirin and 45-55% unknown. But the percent recovery for the experiment was 75.7% meaning 24.3% of components were lost during the experiment. There are many possible sources of error in this experiment and a huge amount of

error is contributed to all the different transfers. Each time the compound was transferred a small amount was left behind. One other source of error could have been the incomplete mixing with dichloromethane or incomplete extraction or precipitation of the aspirin.

Conclusion

Panacetin used in this experiment was separated according to the flow chart below:

“Panacetin” (sucrose, aspirin, unknown)

Mix with dichloromethane, filter

Solid Residue

Filtrate

sucrose

Aspirin and unknown in dichloromethane Extract with NaOH

Aqueous Layer

Sodium acetylsalicylate in water Add HCI, filter

aspirin

Organic Layer Unknown in dichloromethane evaporate

unknown

According to the results of the experiment the percent composition of sucrose was determined to be 12.28%, aspirin 39.5% and the unknown 48.24%. Observations recorded for percent composition and percent recovery supports the hypothesis that the ‘label is accurate’. However

there was a percent recovery of only 75.7% due to the fact that some of the components were lost during transfer to the containers....