One of the most popular reactions within the “click chemistry” concept is the azide- alkyne Huisgen — Physical Chemistry — Thermodynamics Chemistry Question

One of the most popular reactions within the “click chemistry” concept is the azide^-
alkyne Huisgen dipolar cyclo addition using a copper(I) catalyst. The procedure given
below is an example for copper(I) catalyzed triazole formation considered as a “click
chemistry” concept.

[VISUAL]

Chemicals and reagents
• Benzyl azide, C₆H₅CH₂N₃
• Phenyl acetylene, C₆H₅C≡CH
• Copper(II) sulfate pentahydrate, CuSO₄ · 5 H₂O
• Sodium ascorbate, NaC₆H₇O₆
• Aqueous ammonia solution, NH₃(aq), 10% wt
• tertiary^-Butylalcohol, (CH₃)₃COH

Apparatus and glassware
• Screw-top vial 20 cm₃
• Pasteur pipettes
• Stirring bar
• Plastic syringes (1 and 2 cm₃)
• Graduated cylinder
• Thermometer
• TLC pre-coated silica gel plates (Silica Gel PF^-254)
• Heater and stirrer
• Buchner funnel

Procedure
1. Dissolve 133 mg (1 mmol) of benzyl azide in 1 cm₃ of tBuOH : water (1 : 1) solution and add via syringe in a 20 cm₃ screw-top vial having a stirring bar.
2. Close the cap and add followings to the reaction vial via a syringe through PTFE (cap liner) of the cap.
a) 1 mmol of phenyl acetylene dissolved in 1.0 cm₃ of tBuOH : water (1:1) solution.
b) 9.8 mg (10 mol %) of sodium ascorbate in 0.5 cm₃ of tBuOH : water (1:1) solution.
c) 2 – 3 drops (~5 mol %) of 1.0 mol/L aqueous copper(II) sulfate pentahydrate.
3. Stir the mixture at 60 oC for 1 – 2 h until completion by TLC (use ethyl acetate: heptane 1 : 2 mixture as an eluent).
4. Dilute the reaction mixture with 10 cm₃ of ice water and add 2.0 cm₃ of 10% wt aqueous ammonia solution. Stir for another 5 min and collect the solid precipitate with a Buchner filter and air-dry overnight.