PREPARATION OF PHTHALAMIDE FROM PHTHALIC ANHYDRIDE
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Phthalimide is acidic because its conjugate base is resonance stabilized. Phthalimide is slightly soluble in water but it becomes completely soluble when the base is added. Its chemical formula is C6H4(CO)2NH. Bromine is an electrophile as it is electronegative and bromide is a good leaving group.
Phthalimide is easily deprotonated by a base especially a hydroxide base to give the corresponding anion. This reacts with bromine to give N-Bromo-phthalimide as a product.
This is the method to prepare primary aliphatic amines. Phthalimide is converted into its potassium salt by treatment with alcoholic potassium hydroxide (KOH). There are some methods through which phthalimide can be prepared.
- By heating Phthalic anhydride with alcoholic ammonia
- treating Phthalic anhydride with ammonium carbonate or urea
- ammoxidation of O-xylene
Phthalic anhydride is a cyclic dicarboxylic anhydride. It acts as an allergen. Phthalic anhydride is an organic compound with the chemical formula C6H4(CO)2O.
A phthalic anhydride is a commercial form of Phthalic acid as it was the first-ever anhydride that was used commercially. It is a white solid in the physical state which is an important commercial compound as it is widely used for the production of plasticizers for plastic. Phthalic anhydride is obtained from the oxidation of naphthalene in the chemical industry by using fuming acid and mercury as a catalyst. It can also be prepared by the vapor phase oxidation of naphthalene in atmospheric oxygen.
There are two methods to perform an experiment
- The mixture is taken in round-bottom flask near about 500g
- A solution of 3.4 moles of Phthalic anhydride is prepared and added to the flask
- A solution of 6.6 moles of ammonia (NH3) is also prepared and poured into the flask
- This flask is fitted in an air condenser at least with a diameter not less than 10 mm
- This flask is heated with a free flame at 300o C till the mixture becomes in the state of quiet fusion
- To remove water completely,it requires about one hour
- When the temperature reaches 300o C for about one to two hours, the mixture becomes homogeneous melt
- Occasionally shaking of the flask is necessary
- Some material sublimes into the condenser and must be pushed down with a glass rod
- Now the hot mixture is poured into a crock which must be covered with paper to prevent the loss by sublimation
- It allowed cooling to get the final product
- This product is practically pure which melts at 232-235oC
- The theoretical yield is 95-97 % which is 470-480 g
- Phthalimide can also be prepared from ammonium carbonate
- For this 3.4 moles of Phthalic anhydride and 4.4 moles of ammonium carbonate which should be in mortar form
- The remaining steps of the procedure are the same as when ammonia is used.
- Frequently shaking is necessary and sublime material must be pushed back into the reaction flask
- About two hours are required for the completion of the reaction
Phthalic anhydride is formed from the oxidation of naphthalene by using V2O5 at a high temperature at 500o C
Phthalic anhydride is then treating with urea yields Phthalimide.
- When Phthalic anhydride was treated with alkaline hydrogen peroxide in cold condition and the mixture then acidified mono-per-Phthalic acid is obtained.
- Phenolphthalein can be prepared by the condensation of Phthalic anhydride and two moles of phenol in acidic conditions.
SYNTHESIS OF GLUCOSAZONE FROM GLUCOSE
Osazone is a class of carbohydrate derivatives found in organic chemistry. These are formed when reducing sugars react with an excess phenyl-hydrazine at boiling temperature. Osazones synthesis was developed by Emil-Fischer, a German chemist. He obtained that product when he used the reaction as a test to identify monosaccharides. Osazones have a different stereochemistry which differs from monosaccharides by only one chiral carbon.
Osazones are colored and highly crystalline compounds therefore can be easily detected. Each Osazone has its own crystal formation. Some examples are given below.
- Glucosamine forms broomstick or needle-shaped crystal
- Lactosazone forms powder puff-shaped crystal
- Maltosazone forms petal-shaped crystals
Formation of Osazones:
The reaction involves the formation of two phenyl-hydrazones with the oxidation of hydroxyl group on the alpha carbon. This formation allows two sugars i.e. with closely related structures, to give the same Osazone. For example, glucosamine and fructosamine are identical because the reaction requires a free carbonyl group. Only reducing sugars undergo this reaction. Non-reducing sugars for example sucrose is unable to form Osazones. So it can be used to test the nature of carbohydrates either reducing or non-reducing.
The mechanism involves two steps. From each step, phenyl-hydrazone is formed.
- In the first step, a molecule of phenylhydrazine reacts with carbonyl group present on sugar to form a phenyl-hydrazone with the elimination of water molecule
- The second step involves two molecules of phenyl-hydrazine which, first oxidizes the hydroxyl group on the alpha carbon and second then forms a hydrazone with it.
Then end product is stabilized by hydrogen bonding as
- First of all 2 ml of acetic acid is mixed with 2 ml of phenylhydrazine and add 5 ml of distilled water
- The solution is shaken till the phenylhydrazine acetate is obtained
- 1 g of glucose is added n 5 ml distilled water then pour it into the mixture
- This reaction mixture is then heated at water bath
- Yellow-colored crystals of glucosazone begin to crystalline out after 15 minutes of heating
- Heating should be continued for 45 minutes with gentle stirring
- Now the solution is filtered, washed with water, and then with a few ml of methanol
- The yield of glucosazone is about 1.5 g
- The purification is performed by recrystallization from a large amount of methanol or ethanol, producing bright yellow crystals whose melting points are 204oC
- The reaction between acetone and aniline gives N-phenyl propane-2-imine.
- The reaction of a carbonyl compound with 2,4-dinitrophenylhydrazine gives 2,4-dinitrophenylhydrzone. This is an identification test for the carbonyl compound.