Theme: Pharmaceutical analysis of amides and alkyl ureides of benzenesulfonic acid as drug substances: synthesis, properties, analysis, storage, action and use.

 

 

 

 Derivatives of benzenesulphonic acid

         Sulphatic acid – H₂SO₄ HO–SO₂–OH HO–SO₃H

         Benzenesulphonic acid (sulphobenzoic acid) – product of substotution of one group in a molecule of sulphatic acid on benzene ring –С₆Н₅:

                   С₆Н₅–SO₂–OH     С₆Н₅–SO₃H         Graphic formula:

 

Introduction sulphonic group–SO₃H in aromatic ring gives to substance of acid properties, promotes its solubility in water and lowers toxicity.

         Benzenesulphonic acid forms series of derivatives, among which there are important drugs – derivatives of amides (chloramines, pentosept (pantocidum)) and alkyl ureides (chlorpropamide, tolbutamide (butamidum), carbutamide, glibenclamide).

 

Chlorderivatives of amides benzenesulphonic acid

 

Amide of  benzenesulphonic acid: С₆Н₅–SO₂–NH2

 

Chlorderivatives of amides benzenesulphonic acid have the general formula:

Where     R – H, COOH

                R₁ – Na, Cl

Substitution of one or two atoms of the Hydrogene in benzene sulphonamide group to Chlorine leads to formation of labile compounds – chloramines, which easily decay with allocation of “active chlorine” which shows oxidising properties. Therefore chloramine have antiseptic and disinfectant properties.

         Are known various chloramine.

1. Chloramine and dichloramine (the letter B mean, that initial raw materials for synthesis is benzene, it is developed at us)

                            Chloramine                                 dichloramine

         2. Chloramine Т and dichloramine Т (letter Т means, that initial raw materials for synthesis is toluene, it is developed abroad).

                 

Chloramine Т                                     dichloramine Т

Dichloramine have larger of active chlorine.

         The essence of action chloramine consists that they in the water medium hydrolyze with formation HClO, which shows strong oxidising properties at the expense of oxygen disintegration:

HClO ® HCl + O       2HClO ® 2HCl + O₂

Or allocation of “active chlorine” Cl₂:

2HOCl ® Cl₂ + Н₂O₂  ®  Cl₂ + Н₂O + О 

or

4HOCl ® 2Cl₂ + 2Н₂O + О₂ 

         Similar action have hypochlorites, for example, sodium hypochlorite NaClO which in water hydrolyzes to hypochlorite acid:

NaClO + НОН Û NaОН + НСlO

         But advantage chloramines before hypochlorites consists that they do not form some alkali NaОН, which corrodes a wound surface.

 

                            

Chloramine T   Chloramine; the sodium salt of N-chlorotoluene-p-sulphonamide; C₇H₇ClNNaO₂S,3H₂O = 281.7

General reagent grade of commerce.

 

                                     

 Chloramine T                              SPU

Сhloraminum

 

 

 

 

 

 

 

C₇H₇ClNNaO₂S, 3H₂0                                              М m. = 281,7 g/mol

The chemical name: sodium salt of N-chlorotoluene-p-sulphonamide, sodium N-chlor-4-methylbenzol-sulphoneimide trihydrate, N-chlorobenzene sulphonamide-sodium trihydrate.

Chloramine contains not less than 98,0 % and no more than 103,0 % of sodium salt of N-chlorotoluene-p-sulphonamide trihydrate.

Syntesis

Synthesis chloramine from toluene. The synthesis scheme consists such stages:

1) Synthesis of  p-toluene sulphonyl chloride (p-toluene sulphonamide) at interaction of toluene С₆Н₅СН₃ with sulphuric chlorohydrin HO–SO₂–Cl:

 

2) Synthesis amide of  p-toluenesulfonic acid (p-toluene sulphonamide) as result of interaction p-toluene sulphochloride with ammonia NH₃:

Precipitate of  p-toluene sulphonamide filteres and washes out water from chlorides.

3) Chlorination p-toluene sulphonamide at processing it by solution of           sodium hypochlorite NaClO:

In reactionary mix there should not be surplus NaClO as alkali NaOН formed at its hydrolysis (see above) changes course of reaction towards formation of the compound, which do not have active chlorine, and atom of the Hydrogene amido group shows irritating action.

Not to admit this reaction, in the third stage of synthesis to a reactionary mix add the concentrated of solution sodium chloride NaCl.

Properties

   The description. SPU. A crystal powder white або white colour with a yellowish shade.

Solubility. Freely soluble in water R, soluble in 96 % alcohol R, it is practically insoluble in  ether R.

 

On air chloramine decays under the influence of carbonic gas СО₂ and it is audible has begun to smell chlorine (І) oxide Cl₂O:

At fast heating chloramine decays with explosion and flash.

Identification

A. Hydrolisis of chloramine and action of a water solution on indicators.

1 g of chloramine place in a conic flask with volume of 50 ml and dissolve in water, free from СО₂, R  and lead up volume of  solution the same solvent to 20 ml. The received solution paints red litmus paper R  in dark blue colour, and then gradually decolours it.

It is possible to confirm occurring processes with such equations. Water solutions of chloramine have alkaline reaction (рН = 8,0–10,0), because in water the chloramine partially hydrolyzes with formation of alkali NaOH:

H₃C–С₆Н₄–SO–NСl–ONa + HOH ® H₃C–С₆Н₄–SO₂–NH₂  +  NaСlO

NaClO + НОН Û NaОН + НСlO

Therefore the litmus paper in water solution of chloramine is painted in dark blue colour, and phenolphthalein becames crimson colouring.

The further decolouration of litmus paper is possible explaines oxidising properties НСlO, in particular, its acid and chloric decay (disintegration):

2HClO ® 2HCl + O₂­

4HOCl ® 2Cl₂ + 2Н₂O + О₂

B. To 10 ml of solution S (substance solution in water, free from СО₂, R) add 10 ml solution of  hydrogene peroxyde diluted R Н₂О₂; the white precipitate, which is dissolved at heating, is formed. The received hot solution filter, cool. The formed white crystals, which washed out and have been dried up at temperature from 100 °C to 105 °C, should have melting point 137 °C – 140 °C.

C. Calcination of chloramine in crucible and revealing in  filtrate of chlorides-ions.

1 g substance place in a porcelain crucible, calcinate, adhering to safety measures from fire. The rest dissolve in 10 ml of water R and filter. The received filtrate gives reaction (a) for chlorides-ions: reaction with solution of AgNO₃ in the medium of diluted HNO₃.

The received filtrate acidify by diluted HNO₃ R and add some drops of  solution AgNO₃ R1; white curdled precipitate AgCl, which is insoluble iitric acid, but freely soluble in ammonia  solution R*  is formed:

 CL – + Ag ⁺ → AgCl ↓

                                                                white curdled precipitate

*For the salts of organic bases solubility test of formed precipitate AgCl spend after filterings and washings of precipitate by water.

AgCl + 2NH₄OH = [Ag (NH₃) ₂] Cl + 2H₂O

At addition HNO₃ white precipitate AgCl again drops out:

[Ag (NH₃) ₂] Cl + 2HNO₃ → AgCl ↓ + 2NH₄NO₃

D. Calcination of chloramine in crucible and revealing in  filtrate of sulphates-ions: reaction with solution of barium chloride BaCl₂ in the medium of diluted  HCl.

To 5 ml of the filtrate received in test C, add 1 ml of diluted HCl R and 1 ml solution of barium chloride R1; the white precipitate is formed:

SO₄^2– + Ba²⁺ ® BaSO₄

                                        white precipitate

The precipitate is insoluble in mineral acids, alkalis.

E. Calcination of chloramine in crucible and revealing in  filtrate of Sodium- ions (reaction b): interaction with methoxyphenylacetic acid reagent (solution of methoxyphenylacetic acid in solution of tetramethyl hydroxide and ethanol); form white crystalline precipitate, soluble in an ammonia solution:

 

                                                                     white

Other reaction

1. Reaction with solution of potassium iodide in the presence of chloroform (identification of chlorine – product of chloric disintegration).

At acidifying of substance solution by means of diluted HCl –  allocates chlorine Cl₂ (chloric disintegration):

At interaction of Cl₂ with solution KI in the presence of chloroform free iodine I₂ is allocated and chloroformic layer becomes violet colouring:

 Cl₂ + 2KI = 2KCl + I₂

Tests 

1. A solution transparency. Solution S (substance solution in water, free from СО₂, R) on degree turbidity should not exceed the standard ІІ.

 2. Chromaticity of solution. Solution S should be transparent and colourless.

 3. рН solution S. From 8,0 to 10,0.

 4. Ortho-derivatives.

5. The rest, insoluble in ethanol. Weight of the dry rest should not exceed 20 mg (2 %).

Assay

Iodometry, substitute titration

Nearby 0,125 g (exact shot) substance place in conic flask with capacity of 250 ml with the ground in glass stopper, dissolve in 100 ml of water R, add 1 g of  KI R and 5 ml of sulphatic acid diluted R H₂SO₄, maintain during 3 mines and titrate with 0,1 M solution of sodium thiosulphate Na₂S₂O₃, using as the indicator  1 ml of starch  solution R.

Cl₂ + 2KI → I₂ + 2KCl;

I₂ + 2Na₂S₂O₃ → 2NaI + Na₂S₄O_6.

Е_m (C₇H₇ClNNaO₂S, 3H₂0) = М m./2

Storage

In air-tight container, at protecting from light, a dry and cool place, at temperature   8 °C-15 °C.

Action and use. External antiseptic and deodorant.

Apply to treatment of the infected wounds (1,5–2 % solutions – washing of wounds, wetting of tampons and napkins), disinfection of hands (0,25–0,5 % solution), processings of nonmetallic toolkit, disinfecting of subjects of care by patients (1–3 % solution), at a tubercular infection (5 % solution).

For disinfection sometimes use the “activated” chloramine solutions: addition of ammonia NH₃, sulphate ammonium (NH₄) ₂SO₄ or ammonium chloride NH₄Cl strengthens bactericidal properties of solutions.

 

 

                                            

                                                           SP Х

  Pantocidum

Pantosept*

Halazone

 

 

 

 

 

C₇H₅Cl₂NO₄S                                                                             

 М m. = 270,09 g/mol

                                                     Not less than 50 % of active chlorine

The chemical name: N-dichlor-p-carboxy-benzene-sulphonamide, p-dichlorsulphoaminebenzoic acid. Pantosept is derivative of dichloramine.

Synthesis

Synthesis of pantocidum from toluene. The synthesis scheme consists of such stages.

1) Synthesis of  p-toluene sulphonyl chloride (p-toluene sulphonamide) at interaction of toluene С₆Н₅СН₃ with sulphuric chlorohydrin HO–SO₂–Cl:

 

2) Synthesis of amide of  p-toluenesulfonic acid (p-toluene sulphonamide) as result of interaction p-toluene sulphochloride with ammonia NH₃:

Precipitate of  p-toluene sulphonamide filteres and washes out water from chlorides.

 

3) Oxidation p-toluene sulphonamide at processing it by chromic mix (solution of potassium dichromate K₂Cr₂O₇ and concentrated sulphatic acid H₂SO₄) to p-sulphaminebenzoic acid:

4) Passing of  chlorine gas Cl₂ through an alkaline solution p-sulphaminebenzoic acid before full precipitation of pantocidum:

 

Properties

   The description. A white powder with a weak smell of chlorine.

   Solubility. Slightly soluble in water and the diluted acids, freely soluble in solutions of caustic and carbonic alkalis.

     Sodium salt of pantocidum is freely soluble in water. Therefore tablets of pantocidum always contain 50 % of anhydrous sodium carbonate.

Identification

A. Hydrolisis of pantocidum and action of water solution on(with) indicators.     

To 1 g of pantocidum 10 ml of water and 2 drops of  alkaline solution of methyl red. The liquid is painted in red colour and further becomes colourless.

It is possible to confirm occurring processes with such equations. Water solutions of pantocidum have acid reaction because hydrolisis*:

 

Therefore alkaline solution of methyl red is painted in red colour (acid medium).

The further decolouration of methyl red is possible explaines oxidation properties of hypochlorite acid НСlO, in particular, its acid and chloric disintegration (decay):

2HClO ® 2HCl + O₂­

4HOCl ® 2Cl₂ + 2Н₂O + О₂

*It is necessary to notice, that because of bad solubility of pantocidum in water hydrolysis goes slowly.

2. Reaction with solution of potassium iodide in the presence of chloroform (identification of chlorine – product of chloric disintegration).

At acidifying of substance solution by means of diluted HCl –  allocates chlorine Cl₂ (chloric disintegration):

 

At interaction of Cl₂ with solution KI in the presence of chloroform free iodine I₂ is allocated and chloroformic layer becomes violet colouring:

 Cl₂ + 2KI = 2KCl + I₂

 

 

         Tests

1.     The general impurity of heavy metals, Arsenic – within standards.

2.     Sulphatic ashes from 0,5 g of pantocidum should not exceed 0,5 %.

Assay

Iodometry, substitute titration

Nearby 0,2 г g (exact shot) substance dissolve in mix (80 ml of water and 10 ml solution of NaOH), add 15 ml solution of KI and 15 ml of diluted sulphatic acid H₂SO₄. Allocated iodine I₂ titrate with 0,1 M solution of sodium thiosulphate Na₂S₂O₃, using as indicator 1 ml of starch  solution R.

4HOCl 2Cl₂ + 2Н₂O + О₂

Cl₂ + 2KI 2KCl + I₂

I₂ + 2Na₂S₂O₃ → 2NaI + Na₂S₄O₆

E_m = М m. Cl₂/2

Storage

In dense corked containers, at protecting from light, a dry and cool place (not to admit decomposition of drug and reduction of the maintenance of active chlorine).

Action and use. An active antiseptic.

Apply mainly to water disinfecting (the weak smell of chlorine) therefore is audible, using the tablets containing pantocidum 0,0082 g, sodium carbonate anhydrous Na₂CO₃ 0,0036 g and sodium chloride NaCl 0,1082 g. One tablet contains 3 mg of active chlorine. To water disinfecting apply 1 tablet of pantocidum for 0,5–0,75 l of water, and at strong water infection on the same volume of water use – 2 tablets. Disinfecting occurs within 15 minutes.

Use пантоцид also for disinfection of hands (1–1,5 % solutions), syringings and processing of wounds (0,1–0,5 % solutions).

 

 

 

 

 

 

 

Alkyl ureides derivatives of benzenesulphonic acids

        

Benzenesulphonic acid – С₆Н₅–SO₂OH

 

         Urea (carbamide) – amide of  carbonate acid Н₂СО₃

 

         Ureides – N–acyl-derivatives of  urea:

 

 

         Alkyl ureides of benzenesulphonic acids:

        

 

         Alkyl ureides of benzenesulphonic acid reduces of  sugar level in blood and because used to diabetum treatment ІІ type (achrestic diabetes). It is known more than 15 thousand sulfamides with hypoglycemic action, among which the important place occupy sulfanilureas and their derivatives (Chlorpropamide, Tolbutamide, Carbutamide, Glibenclamide).

                                                      

                                              

 

Chlorpropamide

(Ph Eur monograph 1087)

  Chlorpropamidum

 

 

 

 

 

 

 

 

C₁₀H₁₃ClN₂O₃S                                                                          М m. = 276,74 g/mol

                                                                                                                

The chemical name: N – (p-chlorobenzenesulphonyl)-N ‘-propylureas, 1-[(4-chlorophenyl)sulphonyl]-3-propylurea.

DEFINITION

 Chlorpropamide contains not less than 99.0 per cent and not more than the  equivalent of 101.0 per cent of 1-[(4-chlorophenyl)sulphonyl]-3-propylurea, calculated  with reference to the dried substance. 

Synthesis

1. Synthesis chlorpropamide from chlorbenzene. The synthesis scheme consists of such stages.

a) Synthesis of p-chlorobenzene sulphonic-acid chloride at interaction chlorobenzene С₆Н₅Сl with chlorosulphonic acid (sulphate-acid chloride) HO–SO₂–Cl:

 

b) Synthesis of amide of p-chlorobenzene sulphonic-acid  as a result of interaction p-chlorobenzenesulphochloride with ammonia NH₃:

 

c) Condensation p-chlorobenzenesulphamide with urea H₂N–CO–NH₂ and propylamine С₃Н₇NH₂:

2. Synthesis chlorpropamide from chlorobenzene with phosgene use. Synthesis consists of such stages:

a) Synthesis of  p-chlorobenzenesulphamide (see method 1):

 

 

b) Condensation of  p-chlorobenzenesulphamide with phosgene Cl–CO–Cl

 

 

 

 

c) Condensation with propylamine С₃Н₇NH₂:

 

 CHARACTERS

  

 A white, crystalline powder, practically insoluble in water, freely soluble in acetone  and in methylene chloride, soluble in alcohol. It dissolves in dilute solutions of alkali  hydroxides.  

 

 It shows polymorphism.

  

 IDENTIFICATION

  

 First identification C, D.

 

 Second identification A, B, D.

 

  A. Melting point (2.2.14): 126 °C to 130 °C.

 

  B. UV-spectroscopy. Dissolve 0.10 g in methanol R and dilute to 50.0 ml with the same solvent. Dilute 5.0 ml of the solution to 100.0 ml with 0.01 M hydrochloric acid. Dilute 10.0 ml of the solution to 100.0 ml with 0.01 M hydrochloric acid. Examined between 220 nm and 350 nm (2.2.25), the solution shows an absorption maximum at 232 nm. The specific absorption at the maximum is 570 to 630.  

 

  C. Examine by infrared absorption spectrophotometry (2.2.24), comparing with the spectrum obtained with chlorpropamide CRS. Examine the substances prepared as discs. If the spectra obtained show differences, dissolve the substance to be examined and the reference substance in methylene chloride R, evaporate to dryness and record the new spectra using the residues.

 

  D. Mineralization of chlorpropamide and revealing Sulphur and Chloride.

Heat 0.1 g with 2 g of anhydrous sodium carbonate R until a dull red colour appears for 10 min. Allow to cool, extract the residue with about 5 ml of water R, dilute to 10 ml with water R and filter. The solution gives the reaction (a) of chloride (2.3.1) and Sulphur:

a)    Revealing in filtrate of chloride-ions:

CL ^– + Ag ⁺ → AgCl ↓

                                                                white curdled precipitate

AgCl + 2NH₄OH = [Ag (NH₃) ₂] Cl + 2H₂O

[Ag (NH₃) ₂] Cl + 2HNO₃ → AgCl ↓ + 2NH₄NO₃

(This reaction use for difference chlorpropamide from tolbutamide, which does not contain some Chlorine in molecule).

b)    Revealing in a filtrate of sulphate-ions:

To 5 ml of  filtrate add 5 ml of diluted HCl R and 1 ml solution of barium chloride R1; the white precipitate is formed:

SO₄^2– + Ba²⁺ ® BaSO₄

                                        white precipitate

The precipitate is insoluble in mineral acids, alkalis.

 

 

  Other reactions of identification:

1. Alkaline hydrolysis of chlorpropamide and identification of hydrolysis products.

          0,1g of chlorpropamide heat up with 3 drops of solution NaOH; allocated steams (NH₃­) paint the red litmus paper, moistened with water (bring near test tube aperture) in dark blue colour.

                   2. Acid hydrolysis of chlorpropamide and identification of hydrolysis products.

         To 0,5 g of chlorpropamide add 40 ml 50 %  solution of sulphatic acid H₂SO₄ and heat up with a return refrigerator within 30 minutes. Cool in cooler with ice, crystals filter, wash out water before neutral reaction on methyl orange and dry at 100–105 °C within 2 hours. Melting point of syntesed  p-chlorobenzenesulphamide 143–144 °C.

 

 TESTS

  

 Related substances

  

 Examine by thin-layer chromatography (2.2.27), using a suitable silica gel as the  coating substance.  

 

 Test solution Dissolve 0.50 g of the substance to be examined in acetone R and  dilute to 10 ml with the same solvent.  

 

 Reference solution (a) Dissolve 15 mg of 4-chlorobenzenesulphonamide R (chlorpropamide impurity A) in acetone R and dilute to 100 ml with the same solvent.   

 

 Reference solution (b) Dissolve 15 mg of chlorpropamide impurity B CRS in acetone  R and dilute to 100 ml with the same solvent.  

 

 Reference solution (c) Dilute 0.3 ml of the test solution to 100 ml with acetone R.  

 

 Reference solution (d) Dilute 5 ml of reference solution (c) to 15 ml with acetone R.  

 

 Reference solution (e) Dissolve 0.10 g of the substance to be examined, 5 mg of 4-chlorobenzenesulphonamide R and 5 mg of chlorpropamide impurity B CRS in  acetone R and dilute to 10 ml with the same solvent.

 

 Apply to the plate 5 µl of each solution. Develop over a path of 15 cm using a mixture  of 11.5 volumes of concentrated ammonia R, 30 volumes of cyclohexane R, 50  volumes of methanol R and 100 volumes of methylene chloride R. Allow the plate to  dry in a current of cold air, heat at 110 °C for 10 min. At the bottom of a  chromatographic tank, place an evaporating dish containing a mixture of 1 volume of  hydrochloric acid R, 1 volume of water R and 2 volumes of a 50 g/l solution of  potassium permanganate R, close the tank and allow to stand for 15 min. Place the  dried hot plate in the tank and close the tank. Leave the plate in contact with the  chlorine vapour for 2 min. Withdraw the plate and place it in a current of cold air until  the excess of chlorine is removed and an area of coating below the points of  application does not give a blue colour with a drop of potassium iodide and starch  solution R. Spray with potassium iodide and starch solution R. In the chromatogram  obtained with the test solution: any spot corresponding to impurity A is not more  intense than the spot in the chromatogram obtained with reference solution (a) (0.3  per cent); any spot corresponding to impurity B is not more intense than the spot in  the chromatogram obtained with reference solution (b) (0.3 per cent); any spot, apart  from the principal spot and any spot corresponding to impurity A and B, is not more  intense than the spot in the chromatogram obtained with reference solution (c) (0.3  per cent); not more than two such spots are more intense than the spot in the  chromatogram obtained with reference solution (d) (0.1 per cent). The test is not valid  unless the chromatogram obtained with reference solution (e) shows three clearly  separated spots with approximate R_f values of 0.4, 0.6 and 0.9 corresponding to  chlorpropamide, impurity A and impurity B respectively.  

  

 Heavy metals (2.4.8)

  

 Dissolve 2.0 g in a mixture of 15 volumes of water R and 85 volumes of acetone R  and dilute to 20 ml with the same mixture of solvents. 12 ml of solution complies with  limit test B for heavy metals (20 ppm). Prepare the standard using lead standard  solution (2 ppm Pb) prepared by diluting lead standard solution (100 ppm Pb) R with  a mixture of 15 volumes of water R and 85 volumes of acetone R.  

  

 Loss on drying (2.2.32)

  

 Not more than 0.5 per cent, determined on 1.000 g by drying in an oven at 100 °C to  105 °C.  

  

 Sulphated ash (2.4.14)

  

 Not more than 0.1 per cent, determined on 1.0 g.  

  IMPURITIES

  

 

 

 

 

 

 

 

 

  

  A. R = H: 4-chlorobenzenesulphonamide,  

 

  C. R = CO-NH₂: [(4-chlorophenyl)sulphonyl]urea.

  

 

 

 

 

 

 

 

  

  B. 1,3-dipropylurea,

  

 

  Ph Eur

 

 ASSAY

  Alkalimetry, direct titration alcoholic solution

 Dissolve 0.250 g in 50 ml of alcohol R previously neutralised using phenolphthalein  solution R1 as indicator and add 25 ml of water R. Titrate with 0.1 M sodium  hydroxide until a pink colour is obtained.  

 

The method is based on acid properties of a substance at the expense of presence in molecule sulphamide group –SO₂–NH–:

 

 

 

E_m (C₁₀H₁₃ClN₂O₃S) = М m.

 1 ml of 0.1 M sodium hydroxide is equivalent to 27.67 mg of C₁₀H₁₃ClN₂O₃S.

  Other method of assay:

Gravimetry

         After mineralization of chlorpropamide and reconducting (transistorizing) of Sulphur in sulphate-anions (chande S on SO₄^2-), receive precipitate BaSO₄ (weight or gravimetric form), which dry, calcinate to constant weight and weighing. By means of  weight BaSO₄ calculates maintenance of  chlorpropamide in drug.

 

 STORAGE

  

 Store protected from light.  

Action and use

  

 Hypoglycaemic.

  

 Preparation

  

 Chlorpropamide Tablets

  

 Ph Eur

 

 

 

 

 

Tolbutamide

(Ph Eur monograph 0304)                                                                                                                           

 

     Butamidum  

Tolbutamidum           

Diabetol

Diabetamid

C₁₂H₁₈N₂O₃S                                                                                      М m. = 270,35 g/mol                                                                                                                

The chemical name: N – (p-methylbenzenesulphonyl)-N ‘-butylurea, 1-butyl-3-[(4-methylphenyl)sulphonyl]urea.

DEFINITION

 

 Tolbutamide contains not less than 99.0 per cent and not more than the equivalent of  101.0 per cent of 1-butyl-3-[(4-methylphenyl)sulphonyl]urea, calculated with reference  to the dried substance.

Synthesis

Synthesis of tolbutamide from toluene. The synthesis scheme consists of such stages:

1) Synthesis of toluene sulphonyl chloride at interaction of toluene С₆Н₅СН₃ with sulphuric chlorohydrin (sulphate-acid chloride) HO–SO₂–Cl:

 

2) Synthesis of amide of p-toluolsulfonic acid (p-toluene sulphonamide) as result of interaction p-toluene sulphonchloride with ammonia NH₃:

 

3) Condensation Na–p-toluene sulphonamide with butyl isocyanate*               С₄H₉–N=C=O, and then interaction with chloride acid HCl:

 

* Butyl isocyanate С₄H₉–N=C=O sintesed from butanol С₄H₉OН at interaction with phosphorus (V) oxochloride POCl₃, and then potassium cyanate K–O–CΞN:

3С₄H₉OН + POCl₃ = 3HCl + (С₄H₉O) ₃P=O – tributyl phosphate

                                                                  potassium dibutyl phosphate

 

 CHARACTERS

  

 A white, crystalline powder, practically insoluble in water, soluble in acetone and in  alcohol. It dissolves in dilute solutions of alkali hydroxides.

  

 IDENTIFICATION

  

 First identification A, C.

 

 Second identification A, B, D.

 

  A. Melting point (2.2.14): 126 °C to 130 °C.

 

  B. UV-spectroscopy. Dissolve 25.0 mg in methanol R and dilute to 100.0 ml with the same solvent. Examined between 245 nm and 300 nm (2.2.25), the solution shows three absorption maxima, at 258 nm, 263 nm and 275 nm, and a shoulder at 268 nm. Dilute 10.0 ml of the solution to 250.0 ml with methanol R. Examined between 220 nm and 235 nm, the solution shows a single absorption maximum, at 228 nm. The specific absorbance at this maximum is 480 to 520.

 

  C. Examine by infrared absorption spectrophotometry (2.2.24), comparing with the spectrum obtained with tolbutamide CRS.

 

         D. Acid hydrolysis of tolbutamide and identification its products of hydrolysis.

To 0.2 g add 8 ml of a 500 g/l solution of sulphuric acid R and heat under a reflux condenser for 30 min. Allow to cool. Crystals are formed which, after recrystallisation from hot water R and drying at 100 °C to 105 °C, melt (2.2.14) at 135 °C to 140 °C (p-toluene sulphonamide):

                                                                                                           p-toluene sulphonamide

 

Other reaction of identification:

1. Alkaline hydrolysis of tolbutamide and identification its products of hydrolysis.

          To 0,1 g of  tolbutamide add 5 ml of diluted sulphatic acid H₂SO₄ and boil 3 minutes, then cautiously add 6 ml 30 % solution of NaOH; on surface fat drops butylamine, having characteristic smell, are formed.

 

                                                                                                                 characteristic smell

Besides, allocated steams (NH₃­) paint the red litmus paper , moistened with water

(bring near test tube aperture) in dark blue colour.

3.     Mineralization of chlorpropamide and revealing Sulphur.

In crucible mixes o,2 g of tolbutamide and 0,5 g of mix (K₂CO₃ and KNO₃). A crucible close and the mix is calcinated by 15 minutes on weak fire. After cooling the maintenance of  crucible dissolve in 5 ml of diluted HCl and filteres. To filtrate add o,5 ml  solution of barium chloride; the white precipitate is formed:

SO₄^2– + Ba²⁺ ® BaSO₄

                                        white precipitate

The precipitate is insoluble in mineral acids, alkalis.

 

TESTS

 Appearance of solution

  

 Dissolve 0.2 g in 5 ml of dilute sodium hydroxide solution R and add 5 ml of water R.  The solution is clear (2.2.1) and colourless (2.2.2, Method II).

  

 pH (2.2.3)

  

 To 2.0 g add 50 ml of carbon dioxide-free water R and heat at 70 °C for 5 min. Cool  rapidly and filter. The pH of the filtrate is 4.5 to 5.5.

  

 Related substances

  

 Examine by thin-layer chromatography (2.2.27), using silica gel G R as the coating  substance.

 

 Test solution Dissolve 0.50 g of the substance to be examined in acetone R and  dilute to 10 ml with the same solvent.

 

 Reference solution (a) Dissolve 15 mg of toluenesulphonamide R in acetone R and  dilute to 100 ml with the same solvent.

 

 Reference solution (b) To 5 ml of the test solution add 5 ml of reference solution (a).

 

 Apply to the plate 5 µl of the test solution and of reference solution (a) and 10 µl of  reference solution (b). Develop over a path of 15 cm using a mixture of 2 volumes of  anhydrous formic acid R, 8 volumes of methanol R and 90 volumes of chloroform R.  Dry the plate in a current of warm air and heat at 110 °C for 10 min. At the bottom of  a chromatography tank, place an evaporating dish containing a 50 g/l solution of  potassium permanganate R and add an equal volume of hydrochloric acid

R. Place

  the plate whilst still hot in the tank and close the tank. Leave the plate in contact  with the chlorine vapour for 2 min. Withdraw the plate and place it in a current of cold  air until the excess of chlorine is removed and an area of coating below the points of  application gives at most a very faint blue colour with a drop of potassium iodide and  starch solution R; avoid prolonged exposure to cold air. Spray with potassium iodide  and starch solution R and allow to stand for 5 min. Any spot in the chromatogram  obtained with the test solution, apart from the principal spot, is not more intense than  the spot in the chromatogram obtained with reference solution (a) (0.3 per cent). The  test is not valid unless the chromatogram obtained with reference solution (b) shows  two clearly separated spots.

  

 Heavy metals (2.4.8)

  

 Dissolve 1.0 g in a mixture of 15 volumes of water R and 85 volumes of acetone R  and dilute to 20 ml with the same mixture of solvents. 12 ml of the solution complies  with limit test B for heavy metals (20 ppm). Prepare the standard using lead standard  solution (1 ppm Pb) obtained by diluting lead standard solution (100 ppm Pb) R with  a mixture of 15 volumes of water R and 85 volumes of acetone R.

  

 Loss on drying (2.2.32)

  

 Not more than 0.5 per cent, determined on 1.000 g by drying in an oven at 100 °C to  105 °C.

  

 Sulphated ash (2.4.14)

  

 Not more than 0.1 per cent, determined on 1.0 g.

  

 ASSAY

  Alkalimetry, direct titration alcoholic solution

 Dissolve 0.2500 g in a mixture of 20 ml of water R and 40 ml of alcohol R. Titrate with  0.1 M sodium hydroxide, using 1 ml of phenolphthalein solution R as indicator.

 

E_m (C₁₂H₁₈N₂O₃S) = М m.

 

 1 ml of 0.1 M sodium hydroxide is equivalent to 27.03 mg of C₁₂H₁₈N₂O₃S.

  

  

Other method of assay:

Gravimetry

         After mineralization of tolbutamide and reconducting (transistorizing) of Sulphur in sulphate-anions (chande S on SO₄^2-), receive precipitate BaSO₄ (weight or gravimetric form), which dry, calcinate to constant weight and weighing. By means of  weight BaSO₄ calculates maintenance of  tolbutamide in drug.

 

STORAGE

 Store protected from light.  

Action and use

  

 Hypoglycaemic.

 Preparation

 Tolbutamide Tablets

  

 

 

 

 

Carbutamide

Bucarban

 

Diabecid

 

C₁₁H₁₇N₃O₃S                                                                                     М m. = 271,35 g/mol

The chemical name: N – (p-aminobenzenesulphonyl)-N ‘-butylurea or N – (4-aminobenzenesulphonyl)-N ‘-n-butylcarbamide.

Chemical structure of Carbutamide differs from tolbutamide presence of amino group–NH₂ in p-position benzene ring (instead of methyl group –СН₃).

Synthesis

1. Synthesis букарбана from acetanilide.

 Acetanilide synthesed by meanns of aniline acetylation with the help acetic acid СН₃СООН or acetanhydride (СН₃СО) ₂О:

The synthesis scheme consists of such stages:

a) Interaction acetanilide Н₃С–СО–NH–С₆Н₅ with sulphuric chlorohydrin (sulphate-acid chloride) HO–SO₂–Cl with formation p-acetylaminobenzenesulphonic-acid chloride (ацетсульфанилхлорида):

 

b) Condensation p–acetsulphonylchloride with potassium cyanate K–O–C≡N with formation p–acetaminobenzenesulphonylisocyanate:

c) Reaction with butylamine С₄H₉NН₂ with the next hydrolysis acetylcarbutamide with formation carbutamide:

 

 

Properties

   The description. A white crystal powder. Melting point 140–143 °C.

   Solubility., freely soluble in alkalis (presence in molecule sulphamide group–SО₂–NH–) and the diluted mineral acids (presence amino group –NH₂), soluble in alcohol.

Identification

1. Reaction of  primary aromatic amino group (SPU) (syntesis azo dye by means of reaction diazotization with the next azocoupling).

Some crystals of test substance dissolve in 2 ml of HCl R (Carbutamide insoluble in water), add 0,2 ml solution of sodium nitrite NaNO₂ R and through 1–2 mines add 1 ml of alkaline solutionb-naphthol; there is intensive orange or red colouring and, as a rule, precipitate of the same colour is formed.

                                    Diazonium salt                                           azo dye of  red colour

2. Alkaline hydrolysis of Carbutamide and identification its products of hydrolysis.

          To 0,1 g of Carbutamide add 5 ml of  diluted H₂SO₄ and boil 3 minutes, then cautiously add 6 ml 30 % solution of NaOH; on surface fat drops of butylamine with characteristic smell are formed.

Besides, allocated steams (NH₃­) paint the red litmus paper, moistened with water (bring near  test tube aperture) in dark blue colour.

                                                                                                                 characteristic smell

3. Acid hydrolysis of Carbutamide and identification its products of hydrolysis.

         To 0,5 g of Carbutamide add 40 ml  50 %  solution of sulphatic acid H₂SO₄ and heat up with return refrigerator 30 minutes. On surface fat drops butylamine with characteristic smell are formed and carbonic gas СО₂ is allocated.

                                                                                                                     characteristic smell

         4. Mineralization of Carbutamide and revealing Sulphur.

In crucible mixes o,2 g of Carbutamide and 0,5 g of mix (K₂CO₃ and KNO₃). A crucible close and the mix is calcinated by 15 minutes on weak fire. After cooling the maintenance of  crucible dissolve in 5 ml of diluted HCl and filteres. To filtrate add o,5 ml  solution of barium chloride; the white precipitate is formed:

SO₄^2– + Ba²⁺ ® BaSO₄

                                        white precipitate

The precipitate is insoluble in mineral acids, alkalis.

         5. IR-spectroscopy. The IR-spectrum test substance, received in disks, should correspond to IR-spectrum PSS  Carbutamide.

Assay

 1.  Nitritometry, direct titration

 

 Dissolve 0.200 g in a mixture of 10 ml of hydrochloric acid R and 70 ml of water R, add 1 g of potassium  bromide R. Cool in ice-water and titrate by slowly adding 0.1 M sodium nitrite with  constant stirring.

Determine the end-point electrometrically or by the use of the prescribed indicator:

internal indicators: tropeolin 00 – before yellow colouring, a mix tropeolin 00 and methylen dark blue – transition of red-violet colouring to blue, neutral red – before dark blue colouring.

or

 external indicators: potassium iodide test paper – before dark blue colouring.

 

In parallel spend control experience.

 

 

Carry out the determination of primary aromatic amino-nitrogen:

1) Diazotization of  free aromatic amino group:

2) The excess drop of titrant NaNO₂  reacts with КI of potassium iodide test paper in the medium of HCl with formation of iodine I₂ and consequently potassium iodide test paper becomes blue.

                                T

2NaNO₂ + 2KI + 4HCl à I₂ + 2NO + 2KCl + 2NaCl + 2H₂O

                                 excess drop

Е_m (C₁₁H₁₇N₃O₃S) = М m.

2.  Alkalimetry, direct titration alcoholic solution

 Dissolve 0.400 g in 20 ml of ethanol R. Titrate with  0.1 M sodium hydroxide, using 1 ml of thymolphthalein solution R as indicator before blue colouring.

E_m (C₁₁H₁₇N₃O₃S) = М.m.

 Storage. The list of strong substances. In dense corked  container, in dry place.

Action and use. Oral antidiabetic (hypoglycemic) agent. Carbutamide shows stronger hypoglycemic effect in comparison with tolbutamide, but is more toxic.

         The release form: tablets (0,5 g).

    

 

 

 

Glibenclamide

(Ph Eur monograph 0718)                                                                                                                           

Glibenclamidum

Maninil*

Daonil*

C₂₃H₂₈ClN₃O₅S                                                             М m. = 494,0 g/mol

DEFINITION

  

 1-[[4-[2-[(5-Chloro-2-methoxybenzoyl)amino]ethyl]phenyl]sulphonyl]-3-cyclohexylurea.

  

 Content

  

 99.0 per cent to 101.0 per cent (dried substance).     

 

CHARACTERS

  

 Appearance

  

 White or almost white, crystalline powder.

  

 Solubility

  

 Practically insoluble in water, sparingly soluble in methylene chloride, slightly  soluble in alcohol and in methanol.

  

 IDENTIFICATION

  

 First identification A, C.

 

 Second identification A, B, D, E.

 

  A. Melting point (2.2.14): 169 °C to 174 °C.

 

  B. UV-spectroscopy. Dissolve 50.0 mg in methanol R, with the aid of ultrasound if necessary, and dilute to 50.0 ml with the same solvent. To 10.0 ml of the solution add 1.0 ml of a 103 g/l solution of hydrochloric acid R and dilute to 100.0 ml with methanol R. Examined between 230 nm and 350 nm (2.2.25), the solution shows an absorption maximum at 300 nm and a less intense maximum at 275 nm. The specific absorbances at the maxima are 61 to 65 and 27 to 32, respectively.

 

  C. Infrared absorption spectrophotometry (2.2.24).

 

 Preparation Discs of potassium bromide R.

 

 Comparison glibenclamide CRS.

 

 If the spectra obtained show differences, moisten separately the substance to be  examined and the reference substance with methanol R, triturate, dry at 100-105 °C  and record the spectra again.

 

  D. Thin-layer chromatography(2.2.27).

 

 Test solution Dissolve 10 mg of the substance to be examined in a mixture of equal  volumes of methanol R and methylene chloride R and dilute to 10 ml with the same  mixture of solvents.

 

 Reference solution Dissolve 10 mg of glibenclamide CRS in a mixture of equal  volumes of methanol R and methylene chloride R and dilute to 10 ml with the same  mixture of solvents.

 

 Plate TLC silica gel GF₂₅₄plate  R.

 

 Mobile phase alcohol R, glacial acetic acid R, cyclohexane R, methylene chloride R  (5:5:45:45 V/V/V/V).

 

 Application 10 µl.

 

 Development Over a path of 10 cm.

 

 Drying In air.

 

 Detection Examine in ultraviolet light at 254 nm.

 

 Results The principal spot in the chromatogram obtained with the test solution is  similar in position and size to the principal spot in the chromatogram obtained with  the reference solution.

 

  E. Fluorescence of test substance solution in sulphatic acid. Dissolve 20 mg in 2 ml of sulphuric acid R. The solution is colourless and shows blue fluorescence in ultraviolet light at 365 nm. Dissolve 0.1 g of chloral hydrate R in the solution. Within about 5 min, the colour changes to deep yellow and, after about 20 min, develops a brownish tinge.

  

 TESTS

  

 Related substances

  

 Liquid chromatography (2.2.29).

 

 Test solution Dissolve 25.0 mg of the substance to be examined in methanol R and  dilute to 10.0 ml with the same solvent. Prepare immediately before use.

 

 Reference solution (a) Dissolve 5.0 mg of glibenclamide impurity A CRS and 5.0 mg  of glibenclamide impurity B CRS in methanol R and dilute to 100.0 ml with the same  solvent. Dilute 5.0 ml of the solution to 20.0 ml with methanol R.

 

 Reference solution (b) Dilute 2.0 ml of the test solution to 100.0 ml with methanol R. Dilute 5.0 ml of this solution to 50.0 ml with methanol R.

 

 Reference solution (c) Dissolve 5 mg of gliclazide CRS in methanol R, add 2 ml of  the test solution and dilute to 100 ml with methanol R. Dilute 1 ml of this solution to  10 ml with methanol R.

 

 Column: 

  —size: l = 0.10 m, Ш = 4.6 mm,

  

  —stationary phase: spherical base-deactivated end-capped octadecylsilyl silica gel for chromatography R (3 µm),

  

  —temperature: 35 °C.

 

 Mobile phase:

  —mobile phase A: mix 20 ml of a 101.8 g/l solution of freshly distilled triethylamine R adjusted to pH 3.0 using phosphoric acid R, and 50 ml of acetonitrile R; dilute to 1000 ml with water R,

  

  —mobile phase B: mobile phase A, water R, acetonitrile R (20:65:915 V/V/V),

  

 

 

 

 

 

 

 

 

 

 

 

 

  

 Flow rate 0.8 ml/min.

 

 Detection Spectrophotometer at 230 nm.

 

 Injection 10 µl.

 

 Relative retention with reference to glibenclamide (retention time = about 5 min):  impurity A = about 0.5; impurity B = about 0.6.

 

 System suitability Reference solution (c):

  

  —resolution: minimum 5.0 between the peaks due to glibenclamide and gliclazide.

 

 Limits:

  —impurity A: not more than the area of the corresponding peak in the chromatogram obtained with reference solution (a) (0.5 per cent),

  

  —impurity B: not more than the area of the corresponding peak in the chromatogram obtained with reference solution (a) (0.5 per cent),

  

  —any other impurity: not more than the area of the principal peak in the chromatogram obtained with reference solution (b) (0.2 per cent), and not more than 2 such peaks have an area greater than half the area of the principal peak in the chromatogram obtained with reference solution (b) (0.1 per cent),

  

  —total of other impurities: not more than 2.5 times the area of the principal peak in the chromatogram obtained with reference solution (b) (0.5 per cent),

  

  —disregard limit: 0.25 times the area of the principal peak in the chromatogram obtained with reference solution (b) (0.05 per cent).

  

  

 Heavy metals (2.4.8)

  

 Maximum 20 ppm.  

 

 1.0 g complies with limit test D. Prepare the standard using 2 ml of lead standard  solution (10 ppm Pb) R.

  

 Loss on drying (2.2.32)

  

 Maximum 1.0 per cent, determined on 1.000 g by drying in an oven at 100-105 °C.

  

 Sulphated ash (2.4.14)

  

 Maximum 0.1 per cent, determined on 1.0 g.

 

IMPURITIES

  

 

 

 

 

 

 

 

 

 

 

  

  A. R = H: 5-chloro-2-methoxy-N-[2-(4-sulphamoylphenyl)ethyl]benzamide,

 

  B. R = CO-OCH₃: methyl [[4-[2-[(5-chloro-2-methoxybenzoyl)amino]ethyl]phenyl]sulphonyl]carbamate.

  

 

  Ph Eur

 

 

 

  

 

ASSAY

  Alkalimetry, direct titration alcoholic solution

 Dissolve 0.400 g with heating in 100 ml of alcohol R. Titrate with 0.1 M sodium  hydroxide, using 1.0 ml of phenolphthalein solution R as indicator, until a pink colour  is obtained.

 

 

 

 

Е_m (C₂₃H₂₈ClN₃O₅S) = М m.

 1 ml of 0.1 M sodium hydroxide is equivalent to 49.40 mg of C₂₃H₂₈ClN₃O₅S.

  

STORAGE

 Store protected from light.  

 

Action and use

  

 Hypoglycaemic.

  

 Preparation

  

 Glibenclamide Tablets

  

 Ph Eur