Category: Practicals

Aim

To determine the percentage purity of a given sample of the tablet.

Principle

Dapsone is a diamino diphenyl sulphone. It is assayed by direct diazotization titration. The free primary amino group present in dapsone is
diazotized by nitrous acid and hydrochloric acid to form an arene diazonium compound. The endpoint can be determined by using an external indicator i.e. starch iodide paper, during titration with sodium nitrite an aromatic primary amine is diazotized. After the endpoint, the drug solution containing a slight excess of nitrite comes in contact with starch iodide paper. It oxidizes iodide into iodine which gives blue colour with starch indicating the endpoint.

Reaction

Procedure

Preparation of 0.1M Sodium nitrite solution

7.5g of sodium nitrite was dissolved insufficient water to be produced 1000ml.

Standardisation of 0.1M Sodium nitrite

0.3g of sulphanilic acid was dissolved in 50ml of 2M hydrochloric acid, 3g of potassium bromide was added, cool in ice and titrate with 0.1M sodium nitrite solution using starch iodide paper as an external indicator.
Each ml of 0.1M Sodium nitrite= 0.01732g of C6H7NO3S.

Assay of Dapsone tablet

20 tablets were weighed and powdered. Tablet powder equivalent to0.25gm dapsone was weighed and dissolved in a mixture of 15ml of 2M
hydrochloric acid. The solution was cooled to about 15oC and carry out sodium nitrite titration using starch iodide paper as an external indicator. The endpoint is the immediate appearance of blue colour.
Each ml of 0.1M sodium nitrite= 0.01241g of C12H12N2O2S.

Report

The Molarity of 0.1M sodium nitrite = __________________
The percentage purity of given dapsone tablet was found to be = ________________

Aim

To determine the percentage purity of a given sample of Metronidazole tablet.

Principle

A substance with very weak acid or basic property does not give a sharp endpoint in an aqueous solution can be titrated with non-aqueous solvents. Non-aqueous titration is based on Bronsted-Lowry theory According to this theory an acid is a proton donor, i.e. a substance which tends to dissociate to yield a proton and a base is a proton acceptor, i.e. a substance which tends to combine with a proton. When an acid HB dissociates it yields a proton together with the conjugate base B of the acid.
Metronidazole is a weak base and it is assayed by non-aqueous titration. When a weakly basic drug is dissolved in an acidic solvent with titration of
perchloric acid, the basic property of a mineral is enhanced. If a strong acid like perchloric acid is added to acetic acid, the acetic acid behaves as a base and combine with a proton donated by perchloric acid to form an onium ion which acts as a strong acid, the onium ion has readily donated the proton to the base. The indicator used in this titration is crystal violet. The use of acetic anhydride in this solution combines with the water molecule to form acetic acid.

Reaction

Procedure

Preparation of Perchloric acid 0.1M

Mixed 8.5 ml of Perchloric acid in 900 ml of glacial acetic acid shake vigorously and continuous stirring. Then added 30 ml acetic anhydride and
make up the volume to 1 litre with glacial acetic acid and allowed to stand for 24 hours before use. The acetic anhydride reacts with the water in perchloric acid and some traces in glacial acetic acid thereby making the resulting mixture practically anhydrous.

Standardisation of 0.1 N Perchloric acid

About 0.5g of Potassium hydrogen phthalate were weighed accurately and transfer in a 100 ml conical flask, previously dried at 120oC for 2 hours.
50ml of glacial acetic acid was added, warmed if necessary, to dissolve the salt completely. Cooled and titrated with 0.1M perchloric acid using crystal violet 0.1ml (2 drops) as an indicator. The endpoint is colour changes from violet to emerald green.
Each ml of 0.1M Perchloric acid = 0.02042g of Potassium Hydrogen Phthalate

Assay of metronidazole

About 3.0g of metronidazole sample was weighed accurately and transfer into a 250ml conical flask, 50ml of Glacial acetic acid was added, warmed
gently. Cooled and titrated with 0.1M perchloric acid using α-Naphthol benzene as an indicator. The endpoint is colour changes from Blue to Blue-green.

Each ml of 0.1M perchloric acid = 0.02042g of Potassium hydrogen Phthalate.

Report

The Molarity of 0.1M Perchloric acid = _____________
The Percentage purity of given metronidazole was found to be = ________________

Aim

To determine the percentage purity of a given sample of Isonicotinic acid hydrazide tablet.

Principle

Isonicotinic acid hydrazide/ isoniazid is an anti-tubercular drug. It is assayed by the direct titration of Potassium bromate with the addition of potassium bromide in the presence of acid medium using hydrochloric acid. During oxidation reaction liberated bromine reacts with isoniazid in an aqueous solution to form isonicotinic acid. Azo dye methyl red indicator is used in this titration, decolourized the red colour is the end point.

Reaction

Procedure

Preparation of 0.0167 M Potassium bromate solution

About 5.566gm of Potassium bromate was dissolved in water and made up to 1000 ml with distilled water.

Standardisation of 0.0167 M Potassium bromate

20 ml of the above solution was transferred in a glass stopper flask and 3 g of Potassium iodide and followed with 3 ml of HCl was added. Allow standing for 5 min, titrate liberated Iodine with 0.1 M sodium thiosulphate adding 3 ml of starch solution TS and the endpoint is approached.

The concentration of 0.0167 M Potassium bromate = (Molarity of Sodium thiosulphate)/(Volume of Potassium bromate)

Assay of Isonicotinic acid hydrazide tablet

Twenty tablets were weighed accurately and pulverized. A weighed quantity of the tablet power equivalent to 0.25 mg INH was transferred into a
clean and dry 100 ml volumetric flask, then sufficient water was added to produce 100 ml. 20 ml of the above solution was taken. Then 100 ml of water, 20 ml of hydrochloric acid and 0.2 gm of Potassium bromide were added. Then titrated slowly with continuous shaking with 0.0167M potassium bromate using 0.05ml of methyl red as an indicator until the red colour disappears.
Each ml of 0.0167M Potassium bromate KBrO3 = 0.003439g of C6H7N3O.

Report

The Molarity of 0.1 M Sodium nitrite
The percentage purity of the given isonicotinic acid Hydrazide tablet was found to be: ______________________

Aim

To prepare and submit hexamine from formaldehyde and calculate its Percentage Yield.

Principle

Hexamine is a heterocyclic organic compound (CH2)6N4. It has a symmetrical tetrahedral cage-like structure. It is prepared by a condensation
reaction between formaldehyde and ammonia.

Reaction

Requirements

• Formaldehyde – 4.7 g
• Ammonia Solution – 7 g

Procedure

About 4.7g of 30% formaldehyde solution was taken in a beaker and add 7g of 24% ammonia solution was until the solution is slightly alkaline. The mixture was heated on a water bath for 5 minutes and allowed to stand for 15 minutes. The solution was filtered and then evaporated on a direct flame using a china dish to a thick paste. The hexamine crystals are obtained and dried. It was recrystallized from water or alcohol. Hexamine forms colourless, odourless crystals, which are soluble in water and 90% alcohol.
Use: Urinary anti-infective agent

Report

Hexamine was prepared and submitted. Report the following
Theoretical Yield:
Practical Yield:
Percentage Yield:

Aim

To prepare and submit tolbutamide from p-toluene sulfonamide and calculate its percentage yield.

Principle

The synthesis of tolbutamide involves the addition reaction of p-toluene sulfonamide and butyl isocyanate in the presence of triethylamine and
tetrahydrofuran.

Reaction

Requirements

• p-Toluene Sulfonamide – 1 g
• Butyl isocyanate – 1 g
• Triethylamine – 1.2 ml
• Tetrahydrofuran – 10 ml

Procedure

About N-butyl isocyanate (1mmol) and triethylamine (1.2mmol) in a round bottom flask containing 10 ml of tetrahydrofuran, kept in an ice bath. To the above mixture p-toluene sulfonamide (1mmol) was added dropwise at 0oc. After completing the addition, the temperature was suddenly raised to 35-45oC and stirred for 3-4 Hrs. Then the solution was filtered. The product was separated and dried. Then it was recrystallised by using Diethyl ether.
Melting Point: 128oC to 129oC
Use: Anti-diabetic

Report

Tolbutamide was Prepared and submitted. Report the Following
Theoretical Yield:
Practical Yield:
Percentage Yield:

Aim

To Prepare and submit chlorobutanol from acetone and calculate the Percentage Yield.

Principle

Chlorbutanol is also known as Chloroketone. It is a trichloro derivative of tertiary butyl alcohol. It is prepared by combination with acetone and
chloroform in the presence of solid potassium hydroxide Chlorobutanol is used as a local anaesthetic in dental preparation and also antiseptic.

Reaction

Requirements

• Chloroform – 11 ml
• Potassium hydroxide – 1 gm
• Acetone – 14 ml

Procedure

About 11 ml of chloroform and 1 gm of solid potassium hydroxide are taken in a round bottom flask shake until the potassium hydroxide dissolves. To this 14 ml of acetone was added and shaken for 15 minutes. Then set aside for half an hour and the crystal of chlorobutanol were separated out.
Melting Point: 95oC – 99oC

Use: Local anaesthetics

Report

Chlorbutanol was Prepared and submitted and reported the following

1. Theoretical Yield =
2. Practical Yield =
3. Percentage yield =

Aim

To Synthesis and submit Synthesis of 7- Hydroxy -4- methyl coumarin.

Principle

A general synthesis of coumarins involves the interaction of a phenol with a β- ketoester in presence of an acid condensing agent (Pechmann
reaction). Concentrated sulphuric acid is usually used as the condensing agent for simple monohydric phenols and β- ketoesters, although phenol itself reacts better in the presence of aluminium chloride. The mechanism of the reaction involves the initial formation of a β- hydroxy ester, which then cycles and dehydrates to yield the coumarin. Polyhydric phenols, particularly here the two hydroxy groups are meta oriented, react with great ease and sulphuric acid is used as the condensing agent with careful temperature control to ensure a good yield.

Reaction

Requirements

• Conc. Sulphuric acid -7.5 ml
• Resorcinol – 1.2 g
• Ethylacetoacetate – 2.4 ml
• Ice – q.s
• Sodium Hydroxide – q.s
• Ethanol – q.s

Procedure

Take 1 litre of concentrated sulphuric acid in 3 litres capacity 3 necked flask fitted with a thermometer, mechanical stirrer and a dropping funnel. Immerse the flask in an ice bath. When the temperature falls below 100C, add a solution of 100 g (0.91 mol) of resorcinol in 134 g (130.5 ml, 1.03 mol) of redistilled ethyl acetoacetate dropwise and with stirring. Maintain the temperature below 100C by means of an ice bath during the addition (2h). Keep the mixture at room temperature for 18 hr and then pour it into a mixture of 2 kg of crushed ice with vigours stirring and add 3 litres of water. Collect the precipitate by suction filtration and wash it with three 25 ml portions of cold water. Dissolve the solid in 1500 ml of 5 per cent sodium hydroxide solution, filter and add dilute 2 M sulphuric acid (about 550 ml) with vigorous stirring until the solution is acid to litmus. Filter the crude 4-methyl-7-hydroxy coumarin at the pump, wash with four 25 ml portions of cold water and dry at 1000C. The yield is 155g (97%). Recrystallise from 95 per cent ethanol: the pure compound separate in colourless needles, m.p. 1850C.

Use

• Laser dye.
• Starting material for production of the insecticide ‘ hymecromone’.

Report

7- hydroxy -4- methyl coumarin was synthesized and the percentage yield was found to be …….. %.

Aim

To synthesis and submit sulphanilamide from p-acetamido benzene sulphanilamide and calculate its percentage yield.

Principle

Sulphanilamide can be prepared by the reaction of P-acetamido benzene sulphanilamide with Hydrochloric acid or ammonium carbonate. The acetamido groups are easily undergoing acid catalysed hydrolysis reaction to form p-amino benzene sulphonamide.

Reaction

Requirements

• Resorcinol – 1.2 g
• Ethyl acetoacetate – 2.4 ml
• Conc. Sulphuric acid – 7.5 ml

Procedure

1.5 gm of 4- acetamido benzene sulphonamide is treated with a mixture of 1 ml of conc. Sulphuric acid was diluted with 2 ml water. This mixture is gently heated under reflux for 1 hour. Then 3ml of water is added and the solution is boiled again, with the addition of a small quantity of activated charcoal. The solution is filtered while hot, and the filtrate is neutralised with powdered sodium carbonate with stirring until all effervescence ceases and the sulphanilamide is precipitated as a white powder. The solution is cooled, filtered, the sulphanilamide washes with water and dried. Finally, crude sulphanilamide is recrystallized from hot water, to get colourless crystals.

Melting Point: 1630C

Category: Bacteriostatic agent

Report

The Sulphanilamide was synthesised and submitted, Reported the following

1. Theoretical Yield =
2. Practical Yield =
3. Percentage Yield =