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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: Zamzen on October 12, 2010, 06:50:04 PM

Title: glucose gets oxides while reducing copper ions
Post by: Zamzen on October 12, 2010, 06:50:04 PM
ok so glucose gets oxidized while reducing copper. the solution is hot and alcalic.
Write the formula for the reaction.  copper ions look like Cu(OH)2 and Cu+ ions as Cu2O.
My attempt at the solution:
CH2OH(CHOH)4CHO + Cu(OH)2 ---I--> Cu2O + CH2OH(CHOH)4COOH
Reasoning; aldehyd into carboxylic acid. My next step is to remove particles that or not involved in the reaction.
CHO + Cu2+ --I--> Cu+ + COO-
oxidation method gives me Carbon goes from +1 to +3.
copper goes from 2+ to 1+.
so 2 copper ions total. and glucose stays the same
CHO + 2Cu2+   ----I---> 2Cu+ + COO-
Next i neutrulize the charge.
3H+ on the right side which gives me 1 water molecule on the left side. Then i add Hydroxide ions since its a basic solution. So 3 extra on both sides.

CHO + 2Cu2+ +H2O + 3OH-   ----I---> 2Cu+ + COO- + 3H+ + 3OH-
CHO + 2Cu2+ + 3OH- -------> 2Cu+  + COO- + 2H2O
From here i think it looks balanced. i add the compounds that were not involved in the reaction and get

CH2OH(CHOH)4CHO + 2CU(OH)2 +  ---> Cu2O + CH2OH(CHOH)4COOH + 2H2O
Which I find extremely well balanced.
My text book states
CH2OH(CHOH)4CHO + 2CU2+ + 5OH- ---> Cu2O + CH2OH(CHOH)4COO- + 3H2O

who is right?
Title: Re: glucose gets oxides while reducing copper ions
Post by: ooosh on October 13, 2010, 01:52:49 AM
Neither is right. Cu(OH)2 is a solid in water, so it may be right  when 2CU2+ + 5OH- shown as 2Cu(OH)2 + OH-.
Title: Re: glucose gets oxides while reducing copper ions
Post by: AWK on October 13, 2010, 02:58:52 AM
Quote
CH2OH(CHOH)4CHO + 2CU(OH)2 +  ---> Cu2O + CH2OH(CHOH)4COOH + 2H2O
Which I find extremely well balanced.
My text book states
CH2OH(CHOH)4CHO + 2CU2+ + 5OH- ---> Cu2O + CH2OH(CHOH)4COO- + 3H2O

Both equations are correct from balancing point of view, but you have a strong alkaline solution and gluconic acid reacts with OH- to form water and gluconate
Title: Re: glucose gets oxides while reducing copper ions
Post by: Zamzen on October 13, 2010, 03:18:13 AM
Cool. So i just add the OH- on both sides and remove the hydrogen from the glucose and that should be correct.

Thank you very much guys.
Title: Re: glucose gets oxides while reducing copper ions
Post by: AWK on October 13, 2010, 03:25:22 AM
Quote from: Zamzen on October 13, 2010, 03:18:13 AM
Cool. So i just add the OH- on both sides and remove the hydrogen from the glucose and that should be correct.

Thank you very much guys.
on the left side