Boron Family Elements Quiz

Group III-A Elements: The Boron Family

• Boron, aluminum, gallium, indium, and thallium are part of the boron family, with boron and aluminum being the most relevant in pharmacy.
• Aluminum is the most common metal and the third most common element in the Earth's crust.

Chemical Properties

• Boron bonding leans towards covalent rather than ionic, making it a metalloid.
• Aluminum forms both covalent and ionic bonds.
• Metals in this group readily oxidize when heated but remain stable at room temperature.
• The oxides can be easily reduced back to their metal form.
• These metals readily react with sulfur and halogens.
• Hydroxides generally exhibit amphoteric properties, except for the first and last elements in the group.

Chemical Equations

• Oxidation:
  • 4M + 3 O2  2 M2O3 (where M represents Al or B)
• Reaction with Halogens:
  • 2M + 3 X2  2 MX3 (where M represents Al or B)
• Reaction with Acids:
  • Al(OH)3 + 3 HCl  AlCl3 + 3 H2O
• Reaction with Bases:
  • Al(OH)3 + NaOH  NaAlO2 + 2 H2O

Identification Test for Aluminum

• When ammonia (NH3) is added, a white gelatinous precipitate of Al(OH)3 forms.
• Al(OH)3 can adsorb dye colors, such as aluminon, producing a red lake.
• Thenard's Blue Test:
  • Co(NO3)2 + NH3  Co(AlO2)2
  • This reaction produces a blue ash, cobalt meta-aluminate.

Compounds and Their Uses

Boron

• Boron is a non-metal and a component of glass.
• Sources:
  • Tincal: Na3BO3
  • H3BO3 (Boric Acid)
• Uses:
  • Crystalline boron's hardness makes it a valuable diamond substitute for glass cutting and gem polishing.

Borates

• Borates react with turmeric paper.
• They are used in vulcanizing rubber.

Boric Acid (H3BO3)

• Also known as "Boracic acid", "Sal sedativum", and "Sal sativum".
• Toxic by ingestion.
• Absorbed through broken skin.
• Pharmaceutical Applications:
  • Buffer in ophthalmic preparations.
  • Tonicity adjusting agent.
  • E-VALUE=0.52.
  • Antiseptic.
  • Eyewash: 2.45% - 2.5%.
  • Boroglycerin glycerite - suppository base.

Boromycin

• Isolated from Streptomyces antibioticus.
• Used as an anti-HIV agent in vitro.

Sodium Borate (Na2B4O7)

• Also known as "Borax" or Sodium tetraborate.
• Uses:
  • Dobell's solution - an astringent or antiseptic wash for the throat and nose.
  • Eye wash.
  • Component of cold cream and sodium borate preparations.

Buffer Systems

• Phosphate Buffer System:

  • Contains dihydrogen and monohydrogen phosphate ions, which are physiological buffer pairs found in the body.
  • Disadvantage:
    • Insoluble phosphate salts of metals like silver (Ag), zinc (Zn), and aluminum (Al).
    • Supports microbial growth.

• Borate Buffer System:

  • Used in preparations containing metals that would otherwise precipitate in the presence of phosphates.
  • Caution: Borates are toxic; these buffer systems are suitable for external preparations, ophthalmic and nasal solutions, but contraindicated in parenteral solutions.

Primary Borate Buffer Systems

• Feldman's Buffer System (pH 7-8.2):
  • Contains boric acid, sodium chloride (for isotonicity), and an alkaline solution containing sodium borate.
• Atkins and Pantin Buffer System (pH 7.6-11):
  • Consists of an alkaline sodium carbonate solution and an acidic buffer solution of boric acid and sodium chloride.
• Gifford Buffer System (pH 6-7.8):
  • Similar to Feldman's, but uses potassium chloride instead of sodium chloride, making it hypotonic.

Aluminum

• Sources:
  • Cryolite: (Na3AlF6, sodium hexafluoroaluminate)
  • Chief source: Bauxite ore
• Pharmaceutical Uses:
  • Deodorant.
  • Protectant.
  • Antiseptic.
  • Antiperspirant.

Aluminum Adverse Effects

• Constipation.
• Toxicity:
  • Shaver's disease/Bauxite pneumoconiosis: A progressive lung disorder caused by exposure to aluminum oxide found in bauxite fumes.

Aluminum Compounds

• Aluminum Chloride: Astringent, antiseptic, and component of deodorant.
• Aluminum Hydroxide (Al(OH)3):
  • Brand names: Amphojel, Cremalin gel.
  • Adverse Events: Constipation, phosphate deficiency.
• Aluminum Phosphate (AlPO4):
  • Brand name: Phosphagel.
  • Antacid, astringent.