INORG CHEM LAB - Complexation and Reduction-Oxidation Reactions

Complexation Reactions

• Occur between metals and ligands.

• Ligands donate lone pairs of electrons to the metal, forming coordinate covalent bonds.

• Metal-ligands complex: A metal atom/ion bonded to one or more ligands.

• Importance in Pharmacy: Complexing agents sequester metal cations, affecting drug quality and stability.

Metallochromic Indicators

• Ligands that change color upon binding specific metal cations.

• Used in pharmaceutical products to detect metal ions.

Oxidizing Agents

• Gain electrons

• Cause other substances to lose electrons

  • ex. disinfectants, antiseptics

• Used in disinfectants and antiseptics to kill microbes

Reducing Agents

• Lose electrons

• Cause other electrons to gain electrons

  • ex. antioxidants in pharmaceuticals

• Act as antioxidants to prevent drug degradation/oxidation

Ligands

• Molecules that change color when they bind to specific metal ions

• Used to detect metal contamination in drugs

Metallochromic Indicators Experiment

Reagents:

• Calcium chloride + Hydroxynaphthol blue + Disodium edetate

• Zinc sulfate + Dithizone + Disodium edetate

• Magnesium sulfate + Eriochrome black + Disodium edetate

Calcium chloride + Hydroxynaphthol blue + Disodium edetate

Solution turns blue, then back to original color after adding disodium edetate.

Zing sulfate + Dithizone + Disodium edetate

Turns red, then color disappears after adding disodium edetate.

Magnesium sulfate + Eriochrome black + Disodium edetate

Turns red, then blue after adding disosdium edetate

Chelating Agents Experiment

• Copper sulfate + Disodium edetate + Sodium hydroxide

• Calcium chloride + Sodium citrate + Sodium phosphate dibasic

• Copper sulfate + Sodium tartrate + Sodiumm hydroxide

Copper sulfate + Disodium edetate + Sodium hydroxide

Copper sulfate forms a precipitate; adding disodium edetate reduces it.

Calcium chloride + Sodium citrate + Sodium phosphate dibasic

More precipitate forms with sodium citrate than water.

Copper sulfate + Sodium tartrate + Sodium hydroxide

More precipitate forms with sodium tartrate than water.

Monodentate Ligands Experiment

• Copper sulfate + Ammonia + Sodium hydroxide

• Zinc sulfate + Sodium cyanide + Sodium carbonate

• Mercuric chloride + Potassium iodide

Copper sulfate + Ammonia + Sodium hydroxide

Precipitate forms faster in ammonia than in water.

Zinc sulfate + Sodium cyanide + Sodium carbonate

Precipitate forms faster in sodium cyanide than in water.

Mercuric chloride + Potassium iodide

Forms a white precipitate; excess KI dissolves it into a colorlesss solution.

Reduction-Oxidation Reactions Experiment

• Ferrous sulfate + Orthophenanthroline + Cerium (IV) sulfate

• Potassium permanganate + Sulfuric acid + Ferrous sulfate

• Potassium dichromate + Potassium iodide + Starch + Sulfuric acid

• Ferrous sulfate + Sodium nitrate

• Mercuric chloride + Tin (II) chloride

Ferrous sulfate + Orthophenanthroline + Cerium (IV) sulfate

Colorless to red.

Potassium permanganate + Sulfuric acid + Ferrous sulfate

Purple to colorless

Potassium dichromate + Potassium iodide + Starch + Sulfuric acid

Forms a blue complex.

Ferrous sulfate + Sodium nitrate

Forms a white precipitate; dissolves with excess nitrite.

Mercuric chloride + Tin (II) chloride

Forms a white precipitate; dissolves with excess tin (II) chloride, causing a color change.