Mass Of Crude During Synthesis Lab Report

Part 1

Table 10: Mass of crude acetaminophen produce during synthesis.

Substance Mass

Crude acetaminophen 2.0222

Table 11: Mole calculation of 4-aminophenol and acetic anhydride.

Compound 4-aminophenol Acetic anhydride Acetaminophen

Mass/ volume used 2.0126 g (1.08 g)/mol x 2.2 ml=2.376 g

-

Molecular weight 109.13 g/mol 102.09 g/mol 151.63 g/mol

Mole (2.0126 g)/(109.13 g/mol)

=0.018 mol (2.376 g)/(102.09 g/mol)

= 0.023 mol

4-aminophenol acts as limiting reagent during the synthesis of acetaminophen. Thus, the theoretical mole of acetaminophen same as the mole of 4-aminophenol present in the starting of reaction. Since, there from the chemical equation, it showed that 1 mole of 4-aminophenol produces 1 mole of acetaminophen.

Percentage

yield = (Actual mol of product)/(Theoretical mol pf product ) x 100%
Actual mole pf acetaminophen = (2.0222 g)/(151.63 g/mol)
= 0.014 mole
Percentage yield of crude acetaminophen = (0.014 mole)/(0.018 mole ) x 100%
= 77.78%
The infrared spectrum of synthesised acetaminophen was similar to the USP grade acetaminophen. Acetaminophen is an amide group, thus a sharp peak of NH bond stretching found at wavenumber 3325.81 cm-1 and 3325.44 cm-1 in synthesised and USP grade acetaminophen infrared spectrum14. The bending of NH bond in synthesised and USP grade acetaminophen showed a peak at wavenumber of 1612.81 cm-1 and 1613.30 cm-1 14. There was two weak broad band found in both spectrum around wavenumber 3200 cm-1. This indicated presence of OH group in the compound14. The aromatic ring breathing gave a numbers of peak from wavenumber range from 1600 cm-1 to 1450 cm-1 14. At wavenumber 1663.50 cm-1 and 1664.71 cm-1 in synthesised and USP grade acetaminophen spectrums, it indicated the presence of carbonyl (C=O) group in the compounds14. A band found at wavenumber 837.24 cm-1 and 837.43cm-1 in synthesised and USP grade acetaminophen showed acetaminophen is a para-substitution compound14. Refer to appendixes 1 and 2 on page
Table 12: Melting point of synthesised and USP grade acetaminophen
Compound Melting point (℃)
Synthesised acetaminophen 160-170
USP grade acetaminophen 160-173

The melting point of synthesised and USP grade acetaminophen do not comply with the USP Monograph.

The melting point on the USP monograph is 168 ℃ to 172 ℃15. The melting point of these two acetaminophen was lower compared to the standard specification it may contain water molecule. The range of melting point for both acetaminophen was wide as well, this should that these two acetaminophen contain not pure enough. It contained two or more compounds in it. The USP grade acetaminophen may contaminated as it used for a period of time.

Table 13: Maximum wavelength of synthesised and USP grade acetaminophen

Compound Maximum wavelength (nm)

Synthesised acetaminophen 244.0

USP grade acetaminophen 246.0

In visualise, maximum wavelength of USP grade acetaminophen should be around 247 nm instead of 246 nm. However, the spectrometer failed to form a peak in the USP grade acetaminophen spectrum at 247 nm. The maximum wavelength of synthesised acetaminophen was 244 nm. This was close to the USP grade acetaminophen. The peak in synthesised acetaminophen does not form a sharp peak as USP grade acetaminophen. This may because the solution was too diluted. This affect the concentration of synthesised acetaminophen in the solution. Refer to appendixes 3 and 4 on page

Diagram 4: TLC of synthsised and USP grade acetaminophen

Rf of synthesised acetaminophen= (5.50 cm)/(5.90 cm )

=

0.93
Rf of USP grade acetaminophen= (5.60 cm)/(5.90 cm )
= 0.94
The retention factor of synthesised acetaminophen was very close to the USP grade acetaminophen. This showed that the purity of synthesised acetaminophen was almost same as USP acetaminophen. The composition in the both acetaminophen were identical.
Table 14: Absorbance of synthesised and USP grade acetaminophen
Compound Absorbance
Synthesised acetaminophen 1.6387
USP grade acetaminophen 0.0008

The synthesised acetaminophen has higher absorbance compared to USP grade acetaminophen. The free 4-aminophenol in the samples absorb the radiation. This indicated that presence of free 4-aminophenol in synthesised acetaminophen was much higher compared to USP grade acetaminophen. The USP monograph stated that absorbance of synthesised acetaminophen solution should not exceed the standard solution which was 0.0008 absorbance15. Purification of synthesised acetaminophen has to carry out a few times, in order to comply the USP monograph standard.
Table 15: Summarize mean, standard deviation and relative standard deviation of ten 500mg tablets.
Tablet length (mm) Thickness (nm) Tablet weight (g)
Mean 17.58 7.30 0.5941
Standard deviation 0.03 0.04 0.0071
% R.s.d 0.17 0.55 1.1951

The standard deviation of length, thickness and weight of the ten tablets were relatively small. The relative standard deviation was 0.17%, 0.55% and 1.1951% for the length, thickness and weight of tablets. This showed the equipment which used to produce this batch of tablets was very high consistency. It produced uniform tablets.
There was some human errors in this experiment. The vacuum filtration was not carry out properly. Some of the crude product was leaked into the conical flask during filtration. The lower the percentage yield of crude product. From the infrared spectrum and melting point of synthesised and USP grade acetaminophen. It showed both of the acetaminophen were not pure. It may contained some water or unreacted starting ingredients in it. The apparatus used to prepare both acetaminophen solution to undergo infrared spectrum was not dry enough. The synthesised acetaminophen might be too diluted during preparing for the ultraviolet spectrum identification step. The USP grade acetaminophen was not handle with care, this make it not fulfilled with the specification of USP Monograph.
The vacuum filtration can be carry out again and two pieces of filter papers should be use to prevent the product from leaking into the conical flask. This may improve the yield of crude acetaminophen. All the apparatus have to be dried properly before use, in order to provide accurate result during the tests. Dilution technique has to practice more, to prevent the solution from too diluted.
Conclusions
The crude acetaminophen and some testes were carried on it.

The percentage of crude acetaminophen was 77.78%. The infrared spectrum of synthesised acetaminophen was similar to the USP grade acetaminophen. The functional groups and type of bonds in acetaminophen were identified. The NH bond stretching at wavenumber 3325.81 cm-1 and 3325.44 cm-1 in USP grade acetaminophen and synthesised acetaminophen. The bending of NH bond formed a band around 1610 cm-1. The presence of carbonyl group in both synthesised and USP grade acetaminophen gave a peak at wavenumber 1663.50 cm-1 and 1664.71 cm-1. Acetaminophen is para-disubstitution, it formed a peak around wavenumber 837cm-1. There were two small broad peaks found in both spectrum around wavenumber 3160 cm-1 to 3210 cm-1, this indicated the presence of OH group in the solutions. The melting point of synthesised and USP grade acetaminophen were 160 ℃-170 ℃ and 160 ℃-173 ℃. Both of these acetaminophen do not comply with the USP monograph melting point which is 168 ℃ to 172 ℃. This indicated there are some impurity presence in both of the synthesised and USP grade acetaminophen. The maximum wavelength of synthesised acetaminophen was 244.0 nm which was close to the wavelength of USP grade acetaminophen. The retention factor of synthesised and USP grade acetaminophen were 0.93 and 0.94. This showed that the purity of synthesised acetaminophen was similar to the USP grade acetaminophen. The absorbance value of synthesised and USP grade

acetaminophen were 1.6387 and 0.0008. The indicated the synthesised acetaminophen contained higher amount of free 4-aminophenol compared to the USP grade acetaminophen. USP monograph stated that absorbance of test solution should not exceed standard solution. In order to comply this specification, crude acetaminophen should undergoes purification for a couple of times. This will that reduce the amount of free 4-aminophenol presence in the solution. The yield can be improved by carry out vacuum filtration again and use two pieces of filter paper instead one. From the infrared spectrum and melting point of synthesised and USP grade acetaminophen, it showed it may contain some water molecules. All the apparatus must be dried properly before use. The USP grade acetaminophen might be contaminated, thus it has wide range of melting point. An unused USP grade acetaminophen should be use or have to handle it with care. This is to prevent any contaminated occurred. Dilution technique has to improve, to prevent a solution from over diluted. The equipment used to manufacture panadol with batch number 1056 has high consistency. The relative standard deviation of length, thickness and weight of the ten Panadol tablets were 0.17%, 0.55% and 1.1951%. This showed that the tablets produced were uniform.