Antihistamines Laboratory: Chemical Analysis of Antihistamines

Antihistamines are medicinal compounds that can reduce pharmacological effects by blocking the entry of histamine into receptor sites in cells. Based on their structure, antihistamines are divided into 5 groups, namely: amino alkyl ether, ethylenediamine, piperazine, propylamine, and phenothiazine. The antihistamine group is basic, insoluble in water, in the basic form it is soluble in chloroform and organic solvents. It tastes bitter, dissolves in HCl to form a salt that is soluble in water and ethanol. A. Color reaction 1. Mayer 2. FeCl3 3. H2SO4concentrated 4. HNO3concentrated 5. Marquis: 2 drops formalin + H2SO4concentrated 6.Frohde reaction:(Amm. Molybdate 0.5% in water) + H2SO4 concentrated 7. Fehling reaction 8. Mandelin 9. Cuprifil 10. P-DAB HCl 11. Parry B. Precipitation/Crystal Reaction Generally, antihistamine crystals react with: Acetone – water, picrate, Reinecket Sour a. Tools and materials Antihistamine compound reagents, test tubes, dropper pipettes, tube racks, glass objects, cover glasses, microscopes, spirit lamps, sublimation rings b. Work procedures 1. Dimenhydrinate (diphenhydramine theoclate) a. Substance + H2SO4dark → orange to red b. Substance + concentrated HCl → weak rosa c. Substance + HNO3concentrated → negative d. Substance + aqua bromine → negative e. Zat + Marquis → yellow to brown f. Zat + Prohde → orange yellow g. Substance + FeCl3→ red brown h. Substance + Aquadest + Cuprifil (NaOH 2 drops + HCl 2 drops + CuSO4 1 drop → positive (blue) i. Substance + Roux→ chocolate j.Crystal Reaction: Picric Acid, water acetone 2. Diphenhydramine a. Substance + H2SO4thick → orange red-red brown (on top there are oil droplets) usually there is a precipitate, when diluting with water the color remains b. Substance + KMnO4heated → smell of dimethylamine c. Substances in HNO3+ H2SO4→ red violet, + water + chloroform, shake → Violet chloroform layer d. Substance + aqua Iod → purplish black e. Zat + Marquis → yellow orange-brown red f. Zat + Frohde → bright yellow g. Zat + Mayer → light purple/light yellow h.Crystal Reaction: Picric Acid(rod crystals) yellow background, K3Fe(CN)6 (stem crystals) greenish background, water acetone 3. Cetirizine a. Substance + H2SO4dark → yellow b. Substance + KMnO4→ light brown c. Substance + CuSO4→ clear solution d. Substance + Aquadest + Cuprifil (NaOH 2 drops + HCl 2 drops + CuSO4 1 drop → positive (blue) e. Substance + I2→ yellow brown f. Substance + Fe Complex → yellowish brown 4. Clortrimeton (Chlorpheniramine Maleate) a. Substance + Aquadest + Cuprifil (NaOH 2 drops + HCl 2 drops + CuSO4 1 drop → positive (blue/blue green) b. Substance + Marquis → yellow c. Zat + Frohde → yellow d. Pyridine Core: Substance + citric acid + Anhydrous acetic acid, heated → (+) red e. Substance + HCl + Mayer → yellow precipitate f. Frohde: yellow g. Substances in water + NaOH (up to base) → blue green h. Substance + p- DAB HCl → yellow/blue green i. Crystal Reaction: Picric Acid, water acetone (needle crystals)white background 5. Avil (Pheniramine) a. Substance + H2SO4strong → Brown/Weak yellow b. Substance + H2SO4+ K2Cr2O7→green c. Substance + FeCl3→ brownish violet red (unstable in alcohol) d. Substance + HNO3concentrated → (-) Brown /Yellow + gas e. Substance + aqua bromine → orange yellow f. Substance + Mayer → precipitate + dilute HCl → insoluble g. Substance + Marquis → yellowish h. Frohde: after a while weak purple i. Substance + CuSO4→ brown j. Substance + DAB HCl → orange yellow k. Match reaction → orange l.Crystal Reaction: Sublimation, Picric Acid, water acetone 6. Cimetidine a. Zat + Nessler, heat → black b. Substance + Sodium Picrate → red c. Dissolve the substance in ethanol + citric acid + anhydrous acetic acid, heat in a water bath (10-15 minutes) → red violet d.Crystal Reaction: Sublimation, Picric Acid, water acetone