[سيد عثمان]

]أشكرك كثيرا يا دكتور / عاطف على المعلومات القيمة زادكم الله من فضله وعلمه
وخاصة هذا الجزء العملي ( تجربة البرمنجانات مع غاز الأسيتيلين واختفاء اللون البنفسجي ) وتكوين حمض فورميك وثاني أكسيد الكربون</span>[/color]Experiment 2. Ethyne Reacts with Permanganate.
Equipment:
• weighing boat, small
Chemicals:
• C2H2(g), 60-mL
• potassium permanganate, dilute aqueous solution (one small crystal per 50 mL water)
Prepare a syringeful of ethyne as described above. Wash the gas several times. Suction 5-mL of the permanganate solution into the C2H2-filled syringe and cap with the syringe cap. Shake the solution vigorously. The pink color of permanganate will disappear and tiny bubbles will be observed in the solution.
Ethyne and permanganate react with cleavage of the carbon-carbon triple bond and formation of the formate ion and the carbonate ion. The stoichiometry for the oxidation by permanganate under neutral or slightly acidic conditions is:
3 C2H2(g) + 8 MnO4-(aq)+ 8 H+(aq) 3 HCOOH(aq) + 3 CO2(g) + 8 MnO2(s) + 4 H2O(l)
If the conditions are neutral or acidic, <span style="color:#FF0000">the formate ion is converted to formic acid and the carbonate ion forms carbon dioxide. Indeed, as the reaction proceeds, tiny bubbles are observed in the aqueous phase.
As a 'control' the reaction between methane or propane and MnO4-(aq) can be tested. Unlike alkenes and alkynes, alkanes do not react with MnO4-(aq).