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Lab Report

Introduction

Rivastigmine is an FDA (Food and Drug Administration, United States) approved drug for treating Alzheimer’s disease (Soiza, Donaldson, & Myint 2018).  Synthesis of rivastigmine takes place via an acetophenone intermediate (Bhanja & Jena 2012) requiring for higher quantities of this intermediate at commercial scale. The aim of this experiment is to synthesize 4-MethoxyAcetophenone using Anisole and Acetyl Chloride via formation of an electrophilic aromatic substitution thereby forming the acylated product. The AlCl3 facilitates the production of electrophile in the reaction.  Further, reductive amination was carried out using 4-MethoxyAcetophenone and dimethylamine to form n,n-dimethoxy-1-(4-methyl phenyl)ethanamine. Further, 4-MethoxyAcetophenone and form n,n-dimethoxyl-1-(4-methylphenyl)ethanamine was purified. The percentage yield of both the compound was determined. Qualitative analysis such as NMR and FTIR was done for -Methyl Acetophenone and for n,n-dimethoxyl-1-(4-methylphenyl)ethanamine. Based on the results and discussion, the acetophenone intermediate, namely the 4-MethoxyAcetophenone can be recommended to the cholinergic drug company for the pilot-scale production along with the qualitative information about n,n-dimethoxyl-1-(4-methylphenyl)ethanamine.

Results

H1 NMR for 4-MethoxyAcetophenone and form n,n-dimethoxyl-1-(4-methylphenyl)ethanamine was recorded and shown in the figure 1 and 2 respectively. The H1 NMR spectrum for n,n-dimethoxyl-1-(4-methylphenyl)ethanamine shows peaks at 1.3 ppm corresponding to alkyl hydrogen, 2.5 ppm aromatic methyl group hydrogen, 3.7 ppm corresponding to methyl hydrogen, 3.8 ppm corresponding to imidazolium hydrogen , 6.8 ppm and 7.2 ppm corresponding to the aryl hydrogen. The spectrum for 4-MethoxyAcetophenone shows peaks at 2.2 ppm corresponding to methoxy carbons hydrogen (carbon next to the C=O), 3.8 ppm corresponds to hydrogen attached to the C=O bond, 7.2 and 7.9 ppm corresponding to the aryl hydrogens.

Figure 1: H1 NMR spectrum for 4-MethoxyAcetophenone

Figure 2: H1 NMR spectrum for n,n-dimethoxyl-1-(4-methylphenyl)ethanamine

C13 NMR for 4-MethoxyAcetophenone and form n,n-dimethoxyl-1-(4-methylphenyl)ethanamine was recorded and shown in the figure 3 and 4 respectively. The C13 NMR spectrum for n,n-dimethoxyl-1-(4-methylphenyl)ethanamine shows peaks at 20 and 40 ppm corresponding to alkanes, 55 ppm corresponding to secondary carbon, 65 ppm for carbon attached to a amine group, 115 and 125 ppm for C=C and aryl carbon respectively, 143 ppm corresponding to C=C and 160 ppm corresponding to carbon attached to the benzene ring. The C13 NMR spectrum for 4-MethoxyAcetophenone shows peaks at 25 ppm and 55 ppm corresponding to methyl carbons, 115 and 125 ppm corresponds to  C=C and aryl carbon respectively, 160 ppm corresponds to C=O and 195 ppm corresponds to RHC=O ketone.

 

Figure 3: C13 NMR spectrum for 4-MethoxyAcetophenone

 

Figure 4: C13 NMR spectrum for n,n-dimethoxyl-1-(4-methylphenyl)ethanamine

 

The Fourier transform infrared spectroscopy for 4-MethoxyAcetophenone and form n,n-dimethoxyl-1-(4-methylphenyl)ethanamine was recorded and simulated respectively and shown in the figure 5 and 6 respectively. The FTIR spectrum for 4-MethoxyAcetophenone shows many peaks, of which the required peaks for confirmation of the structure are 1686 cm-1 for ketone, 1650 cm-1 for the presence of aromatic ring and 1465 cm-1 for the presence of methyl group.  The FTIR spectrum simulated for n,n-dimethoxyl-1-(4-methylphenyl)ethanamine with important peaks at 1200 cm-1 for the presence of amine group, 1686 cm-1 for ketone, 1650 cm-1 for the presence of aromatic ring and 1465 cm-1 for the presence of methyl group. 

 

Figure 5: FTIR spectrum record for 4-MethoxyAcetophenone

Figure 6: FTIR spectrum simulated for n,n-dimethoxyl-1-(4-methylphenyl)ethanamine

 

Discussion

The experiment was conducted as outlined in the method section. The total percentage of yield for 4-MethoxyAcetophenone and n,n-dimethoxyl-1-(4-methylphenyl)ethanamine was found to be 92% and 63% yield respectively. This shows that the friedel crafts reaction gave better yield compared to the reductive amination reaction. The difference in the yield of the reaction may have risen due to the catalytic efficiencies of each reaction and the laboratory conditions. Several studies have shown that the prevailing conditions affect the reaction in synthesis of the product, ultimately affecting the yield of the reaction (Deng et al. 2011, Ansari et al. 2018).

Several reports were used for deducing the peaks in the NMR and FTIR spectra (Martinelli & Nordstierna 2012, Laurie n.d.). 4-MethoxyAcetophenone was confirmed by analysis all the peaks in the C13, H1 and FTIR. For example, H1spectrum identified peaks for methoxy carbons hydrogen (carbon next to the C=O), hydrogen attached to the C=O bond and the aryl hydrogens. 4-MethoxyAcetophenone has 6 hydrogen atoms, a methyl group attached to the oxygen atom at the ortho position of the benzene ring. Moreover, hydrogen is present in the acyl group. C13 spectrum identified C=C in the aromatic ring, as well as the aromatic carbon (at 115 ppm and 125 ppm respectively). The carbon atom of the ketone group was identified using the peak obtained at 195 ppm. Apart from the confirmation from the C13 and H1, the FTIR spectrum shows the presence of strong vibration of the ketone, aromatic and methyl group. All the evidences shows that the product is a 4-MethoxyAcetophenone.

Similarly, H1spectrum for second compound gave peaks for alkyl hydrogen, aromatic methyl group hydrogen, methyl hydrogen, imidazolium hydrogen and aryl hydrogen. It is to be noted that all these hydrogens are present in n,n-dimethoxyl-1-(4-methylphenyl)ethanamine. The C13 spectrums result revealed the presence of alkanes, secondary carbons, amine group and aryl carbon. Additionally, the FTIR spectrum shows the presence of amine group, ketone, aromatic ring and methyl group, all of which are present in the n,n-dimethoxyl-1-(4-methylphenyl)ethanamine. Hence the compound was identified to be n,n-dimethoxyl-1-(4-methylphenyl)ethanamine.

Conclusion

From the results and discussion, it is evident that Methyl Acetophenone and n,n-dimethoxyl-1-(4-methylphenyl)ethanamine was synthesized successfully. The reaction along with the procedure for the synthesis of product is approved for synthesis of Acetophenone intermediate, which in turn can be used for production of Rivastigmine.

Experimental method

A three-necked flask, condenser, HCl trap1 and addition funnel were set up in preparation for the experiment. A stopper was placed on right side of the three-necked flask, the condenser set in the centre and the addition funnel connected to the left side. The HCl trap was connected to the condenser via a downward funnel. DCM (dichloromethane, 25 mL) was combined with anhydrous AlCl3 (14.00 g, 104 mmol) in the three-necked flask. The solution was then cooled to 0 °C (in an ice bath). Then, acetyl chloride (2.8 g, 100 mmol) was combined in an Erlenmeyer flask and swirled with DCM (30 mL). This mixture was then put in addition funnel, then the funnel was sealed with a test tube layered with cotton and calcium chloride, to prevent water from reacting with AlCl3. Acetyl chloride was added over 15 minutes at (0 °C). Anisole (16.12 ml, 150 mmol) was dissolved in DCM (20 mL) and added to the mixture over another 15 minutes. In a separate beaker, HCl (50 ml, 6 M) was combined with ice (100 g). The anisole and acetyl chloride mixture in the flask was pipetted into the beaker and stirred for 20 minutes (at a continued 0 °C).

 

Organic material was run through the separation process. The separated aqueous layer was run through the process again, with an added DCM (60 mL). The collected organic mixture was extracted with aqueous saturated sodium bicarbonate (100 mL). The organic layer was then dried with the use of anhydrous sodium sulphate3. Then, DCM was removed from solution via rotary evaporation. Finally, the residue was purified using a chromatography column. Then, organic matter was combined with a mixture of hexane and ethyl acetate (in a 3:1 ratio) and then added to the column. The eluted products were collected in fractions and categorised by TLC plates. The product was analysed by H1-NMR and IR spectroscopy.

 

The second part of the experiment is to synthesize an amine formed by following the reductive amination process. 4-MethoxyAcetophenone and Dimethylamine were added into the flask containing 15 ml of MeOH under inert/nitrogen atmosphere. The solution was stirred for 1-2 hours. The Sodium cyanoborohydride was added to the flask and stirred for 16 hours.  The stirring is stopped for a while and 20 ml of 1 M HCl was added to the flask and the stirring was continued until the bubbles disappear. The mixture is then separated using separating funnel and extracted with two 10 ml ethyl acetate and discarded. The resulting solution’s pH was adjusted to 10 using 10 M NaOH and extracted with three 10 ml DCM. The organic phase of the solution was washed twice with 10 ml of brine and was subjected to the rotary evaporator to get the crude product.

Acknowledgement

Kindly specify your tutor, class instructor and the lab assistant name as acknowledgement. I hereby extend acknowledgment to Dr. XYZ and Mr. ZYX.

References

Ansari, KB, Arora, JS, Chew, JW, Dauenhauer, PJ, & Mushrif, SH 2018, ‘Effect of Temperature and Transport on the Yield and Composition of Pyrolysis-Derived Bio-Oil from Glucose’, Energy and Fuels, Vol. 32, No. 5, pp. 6008–6021.

Bhanja, C & Jena, S 2012, ‘Synthesis Design of ‘Rivastigmine’-A Potent Therapeutic Agent for Alzheimer’s disease using Retrosynthetic Analysis’, , Vol. 4, No. 6, pp. 3171–3183.

Deng, S, Wang, Z, Gu, Q, Meng, F, Li, J, & Wang, H 2011, ‘Extracting hydrocarbons from Huadian oil shale by sub-critical water’, Fuel Processing Technology, Vol. 92, No. 5, pp. 1062–1067, Elsevier B.V., ,  http://dx.doi.org/10.1016/j.fuproc.2011.01.001.

Laurie, S n.d., ‘California State Polytechnic University , Pomona Dr . Laurie S . Starkey , Organic Chemistry Lab CHM 318L 1 H NMR Chemical Shifts Protons on Carbon Protons on Oxygen / Nitrogen *’, , p. 318.

Martinelli, A & Nordstierna, L 2012, ‘An investigation of the sol-gel process in ionic liquid-silica gels by time resolved Raman and 1H NMR spectroscopy’, Physical Chemistry Chemical Physics, Vol. 14, No. 38, pp. 13216–13223.

Soiza, RL, Donaldson, AIC, & Myint, PK 2018, ‘Vaccine against arteriosclerosis: an update’, Therapeutic Advances in Vaccines, Vol. 9, No. 6, pp. 259–261.

 

Appendix

Code: ORG-02

Name

m/v

n

eq

Mw

C

4 methoxy acetophenone

1.23

0.0087

1

150.17

-

DMA

0.451

0.010

1.2

45.1

2M

NaBH3CN

0.628

0.010

1.2

62.8

-

 

M (Flask+Product): This data has to be collected from the experiment and it cannot be blank. Anyways, I had assumed the weight of the product to be 1.3 grams (92 % yield). Therefore, total weight is 67.7787 +1.300  = 69.0787

M (Product):  1.3 g

N (Product):  1.3/163.26 = 0.007962

Code: ORG-01

Chemical name

m/v

n

eq

MW

D

Methyl benzene

5.0677

0.055

1

92.14

(We normally don’t add anything to it)

Ac.Cl

5.101

0.065

1.1

78.49

100mM in DCM

AlCl3

8.667

0.065

1.1

133.34

-

 

(Normally any one data is needed in eq to find the exact amount of Methyl benzeneto be used. Since there is no other data available, I have to go with the thumb rule: AcCl and AlCl3 are always equimolar and higher than methyl benzene. Hence 1:1.1:1.1 )

M (Flask+Product): This data has to be collected from the experiment and it cannot be blank. Anyways, I had assumed the weight of the product to be 0.8 grams (63 % yield). Therefore, total weight is 67.7787 +0.8  = 122.2765

M (Product):  0.8 g

N (Product):  0.8/97.17 = 0.0082

Short procedure

  • Add 25 ml of DCM and 14 g of 104 mmol Aluminium Chloride (3) in three necked flask, cooled at 0 °C
  • Add acetyl chloride (2) (2.8g, 100mmol) and DCM 30 ml to the flask
  • Add Anisole (1) (16.12 ml, 150mmol) and DCM of 20 ml to the flask.
  • Meanwhile, add HCl (50 ml, 6M) in a beaker and add the mixture from the flask into the beaker.
  • The organic layer was separated and extracted using sodium sulphate (100ml) the process was repeated again with DCM (60 ml).
  • The residual DCM was removed using rotary evaporator.

 

 

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