Methods
There was three different test was performed which were simple test, test for specific elements which was nitrogen and functional groups test.
First of all, before the experiment was started, the table was drawn for recording the observation. The first thing was 5 simple tests were performed for preliminary information regarding on sample drug (81) which was related to functional groups. First was heating the sample on nickel foil, second was damping red and blue litmus paper and finally was solubility of water (6 drops), hydrochloric acid (6 drops) and sodium hydroxide (6 drops). All observation was recorded on the table.
Next test was testing for specific elements which was nitrogen; 5mg of sample was mixed with 5mg of sodium carbonate fusion mixture on a tile, the powder was placed in an ignition tube, a dampen red litmus paper was placed at the top of the tube which was to test the gas being evolved after heating it.
Then next test was functional group tests. First test was phenol group, 5mg of sample was dissolved in ethanol and 1 drop of ferric chloride solution was added. Second test was carbonyl group, 5mg of sample was dissolved in water after warming to facilitate dissolution and was cooled, and then excess 2, 4-dinitrophenylhydrazine reagent was added. Third test was ester group; 5mg of sample, half a pellet of potassium hydroxide, 5mg of hydroxyammonium chloride and 1ml of methanol was added in a micro crucible. However, methanol was not filled more than one third. The micro crucible was heated in a heat block and was evaporated to one quarter bulk. 1 ml of methanol was added and it was repeated twice in evaporation, so overall three times evaporations. 0.5ml of methanol was added to cool and was acidified with hydrochloric acid and ferric chloride solution was added drop by drop. Fourth test was amide group, 5mg of sample and 6 drops of sodium hydroxide solution was added in a micro-beaker and was gently boiled on a heat block, after that heat source was removed and a stripped of red litmus paper was moistened and was placed in the vapour above the solution in the beaker avoiding contact with sodium hydroxide solution. Fifth test was primary aromatic amine group; 5mg of sample was added in a small test tube with one drop of furfural reagent and was allowed to evapourate at room temperature, a crystal of sodium acetate was added before furfural reagent was added. Final test was N-aryl amide; 5mg of sample was mixed with 5 mg of soda line and was placed in an ignition tube. At first was warmed gently and then more strongly until a distillate was approached the mouth of the tube. After that, it was removed from heat and a strip of filter paper with furfural reagent was put in the mouth of the tube.
All the observation in appearance, phase and smell was recorded in the table.
Result
Sample 81
- Soluble in NaOH
- It is acidic in litmus paper
- Contain nitrogen
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Functional groups: phenol OH group, carbonyl group, and amide group.
Discussion
The result shows that the unknown sample is Salicylamide C7H7NO2 which contains functional group of phenol group, carbonyl group and amide group. All the negative result is eliminated, which are primary aromatic amine, N- aryl amide and ester group. So the positive result shows the functional group of Salicylamide is phenol OH, carbonyl and amide group. In phenol group, it shows positive result that it in purple colour which indicates present of phenol in Salicylamide. And in carbonyl group it turns yellow precipitate which show positive result indication carbonyl group is present. And amide group is present as it shows positive result which gives ammonia odour and red litmus paper turn blue. Below shows the equation for the positive results.
Equation:
Nitrogen
R-N2 + Na2CO3 = CO2 + 2 NH3
Phenol OH
R-OH + FeCl3 = 3RCl + Fe (OH)3
Amide
R-NH2+ NaOH=RCOO Na+ +NH3
Carbonyl group
RR'C=O + C6H3(NO2)2NHNH2 → C6H3(NO2)2NHNCRR' + H2O
Salicylamide is insoluble in cold water but soluble in hot water. However, it dissolves completely with sodium hydroxide, so it is freely soluble and Salicylamide is significantly more soluble in strong base.
There is two graphs been taken in UV spectra, one for water and other for sodium hydroxide of Salicylamide. In the first graph, it is hypsochromic effect because it shifts towards a shorter wavelength. This may be caused by a change of medium and also by such phenomena as the removal of conjugation. The second graph is bathochromic effect because it shifts of absorption towards longer wavelength. As sodium hydroxide is more ionised than water. However, the absorbance of water is higher than sodium hydroxide as it shown in the graph.
Salicylamide contain functional group of phenol which also show spectral shift on ionisation. Phenol is weak acid, so ionisation increases the intensity of light absorption and the position of λmax moves to longer wavelength. This is because ionisation and loss of the H atom as an H+ ion results in a full negative charge on the oxygen, which can interact with ring more effectively than the lone pair of electron present in the unionised molecule.
In IR spectra, it is very useful technique in identification of unknown compounds. “ The infrared region of the electromagnetic spectrum refer to light of wavelength 2.5 to 15 μm and the absorption of light by the molecule causes changes in the vibrational energy of the molecule in its ground state. In the graph it shows that it contains functional group of amide, phenol OH and carbonyl group. As it is been labelled in the graph to shows which functional group is present”.
- Essential of pharmaceutical chemistry; edition 4, Donald Cairns, Pharmaceutical Press published 2008 page 179.
Conclusion
To sum it up, the unknown sample is Salicylamide, as the result shows positive results by testing functional group and using IR/UV spectra.
Reference
- Essential of pharmaceutical chemistry; edition 4, Donald Cairns, Pharmaceutical Press published 2008
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Introduction to spectroscopy, 4th edition, Department of Chemistry, Pavia Lampman Kriz Vyvan.
