Abstract
This lab experiment involved P-Methyl-Acetanilide synthesis from acetic anhydride and a solution of sodium acetate. Different techniques were used in this lab exercise including; vacuum filtration, crystallization, and spectral analysis. The main aim of performing this experiment was to synthesise, isolate, evaluate and analyse P-Methyl-Acetanilide product. We synthesised the product and then, isolated the product by the process of the vacuum filtration. We evaluated the products purity by melting point analysis and performed a spectral analysis (1HNMR spectroscopy) later. The 1HNMR spectroscopy interpretation is a method/ technique used to determine the structures of organic compounds that are unknown (Pavia 128). It stands for proton nuclear magnetic resonance (1HNMR), and it provides information concerned in organic compounds. For example, hydrogen types that are present in a molecule, the number of hydrogen present, and the hydrogen’s electronic environment.
There was much to learn from the experiment for example filtration techniques. Filtration is used to remove solid particles or impurities from a solution and to isolate organic solids. We learned that types of filtration mainly used in organic chemistry were vacuum and gravity filtration. Vacuum filtration is said to be faster as compared to gravity filtration since reduced pressure is applied to force the solution and the air through a filter paper. In this experiment, vacuum filtration was used. We followed all the experimental procedures as required and obtained the results. The importance of lab safety was emphasized during the entire experiment to avoid any hazards from occurring.
Objectives
Materials and chemicals
Erlenmeyer flask
Sodium acetate tri-hydrate (CH3CO2Na. 3H2O)
Water
P-toluidine
Hydrochloric acid HCL
Acetic anhydride
Procedures
A solution of sodium acetate was prepared by mixing 2.1597 g of Sodium acetate trihydrate, and 6 ml of water in an Erlenmeyer flask.
The mixture in the Erlenmeyer flask was then swirled vigorously to dissolve. The solution of sodium acetate was put aside to be used later.
1.6127 g of P-toluidine was added to 40 ml of water in a 125-ml Erlenmeyer flask fitted with a stir bar.
With stirring, 1.3 ml of concentrated hydrochloric acid (HCL) was added.
We stirred for 2 minutes.
With stirring, 2.1 ml of acetic anhydride was added, and sodium acetate solution was also added immediately.
The reagents were well mixed by stirring them vigorously.
The product was then cooled in an ice bath. During this time, we continued stirring vigorously until the product crystallized.
The product was isolated by vacuum filtration, and the crystals with several portions of ice-cold water were used to wash the product.
The product was allowed to dry
We weighed the product and saved at least 25mg for spectral analysis and characterization.
For the infrared spectroscopy, a Nujol mull or K Br of the solid was to be prepared, IR spectrum recorded and finally interpreted.
During the NMR spectroscopy evaluation, the product obtained was dissolved in deuterated DMSO. The 1HNMR spectrum for 0-10 ppm was recorded and interpreted. The 1HNMR spectrum for P-Methyl-Acetanilide in the deuterated DMSO was given.
Results and Discussion
The total weight of P-Methyl-Acetanilide synthesised was 1.4845g
We determined the melting point of the dry product and recorded it as;
The melting point of P-Methyl-Acetanilide = 145-150oC
We determined the purity of P-Methyl-Acetanilide product by comparing the theoretical value to the experimental value of the product obtained.
We learned that melting point (M.P) of pure solids was one of the most important characteristics of compounds. The melting point is usually used to identify a product and to determine the purity of a substance. A solid containing impurity exhibits lower and broader melting point (M.P) ranges, but pure solids have sharp melting point characteristics. A substance is impure if it has a melting point (M.P) range greater than5oC. In our case, the P-Methyl-Acetanilide product obtained can be said to be relatively pure. The melting point of a substance can be affected by several factors such as the molecule size and the attraction force existing between molecules. The peaks in the IR spectra are at 0.05ppm, 2.1ppm, 2.3ppm, 7.05ppm and 7.5ppm.
Conclusion
We were able to synthesize the P-Methyl-Acetanilide product on following all the procedures provided carefully and precisely. From the lab experiment, we learnt more about different techniques of vacuum filtration and crystallization process. We obtained the experimental melting point M.P results of the product and compared it to the theoretical melting point (M.P) values. The comparison of the two melting points enabled us to determine the degree of purity of P-Methyl-Acetanilide synthesized from the lab exercise. From the spectral analysis performed, the product was analysed based on its structure. Hydrochloric acid and acetic anhydride are corrosive and might cause burns and therefore gloves and eye protection were provided for safety precautions. At the end of this experiment, we were able to achieve all our objectives, and the lab was, therefore, successful.
Reference
Pavia, Donald L. Introduction to Organic Laboratory Techniques: A Microscale Approach. Belmont, CA: Thomson Brooks/Cole, 2007. Print.
