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Author: Subject: permanganate and toluene reaction
jamit
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[*] posted on 7-4-2011 at 19:04
permanganate and toluene reaction


Can someone help me figure out the balanced chemical reaction for the oxidation of toluene from potassium permanganate?

Here's what I see happening:

2 KMnO<sub>4</sub> + C<sub>7</sub>H<sub>6</sub>O<sub>2</sub> --> C<sub>7</sub>H<sub>5</sub>KO<sub>2</sub> + H<sub>2</sub>O + KOH + 2 MnO<sub>4</sub> (ppt)

The problem is that the chemical equation is not balanced... there's an extra hydrogen and oxygen on the right side of the equation. Putting different coefficient numbers doesn't help either.

Help?

<!-- bfesser_edit_tag -->[<a href="u2u.php?action=send&username=bfesser">bfesser</a>: subscript; "H20"]

[Edited on 3.8.13 by bfesser]
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Lambda-Eyde
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[*] posted on 7-4-2011 at 21:39


Well, for starters, there's no such thing as manganese (VIII) tetroxide. Secondly, you're not supposed to care about spectator ions (K<sup>+</sup> in this case). Try again.

[Edited on 8-4-2011 by Lambda-Eyde]




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[*] posted on 7-4-2011 at 22:03


To start with, you also have benzoic acid, the product, on the reactants side. The end product for the manganse is MnO<sub>2</sub>. Once you get the right starting and ending materials it balances pretty easily.

<!-- bfesser_edit_tag -->[<a href="u2u.php?action=send&username=bfesser">bfesser</a>: subscript]

[Edited on 3.8.13 by bfesser]
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jamit
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[*] posted on 8-4-2011 at 09:27


here's another attempt at the chemical equation:

2 KMnO<sub>4</sub> + C<sub>7</sub>H<sub>6</sub>O<sub>2</sub> --> C<sub>7</sub>H<sub>5</sub>KO<sub>2</sub> + KOH + 2 MnO<sub>2</sub> (ppt) +O<sub>3</sub>??

@mumbles = why is benzoic acid also on the reactant side? isn't it just potassium benzoate whIch I'll then just add HCl to make benzoic acid?

Can someone help me. thanks in advance.

<!-- bfesser_edit_tag -->[<a href="u2u.php?action=send&username=bfesser">bfesser</a>: subscript; "03"]

[Edited on 3.8.13 by bfesser]
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[*] posted on 8-4-2011 at 12:18


Toluene is C<sub>7</sub>H<sub>8</sub>, not C<sub>7</sub>H<sub>6</sub>O<sub>2</sub>.

<!-- bfesser_edit_tag -->[<a href="u2u.php?action=send&username=bfesser">bfesser</a>: subscript]

[Edited on 3.8.13 by bfesser]




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jamit
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[*] posted on 8-4-2011 at 19:45


Stupid of me! thanks querjek!

Ok, the reaction equation is:

2 KMnO<sub>4</sub> + C<sub>7</sub>H<sub>8</sub> --> C<sub>7</sub>H<sub>5</sub>KO<sub>2</sub> + KOH + H<sub>2</sub>O + 2 MnO<sub>2</sub>

Ok, I believe this is now balanced! Thank you all for helping me figure this out!

Yay!!:D:D

<!-- bfesser_edit_tag -->[<a href="u2u.php?action=send&username=bfesser">bfesser</a>: subscript]

[Edited on 3.8.13 by bfesser]
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jamit
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[*] posted on 13-4-2011 at 01:30


Before I do the toluene oxidation with KMnO<sub>4</sub>, I did my final research and found the forum scienceforums.net and there woelen said that you need to acidify the toluene/permanganate mixture with sulfuric acid to increase the overall yield of benzoic acid.

This seems to conflict with several lab info and with some youtube videos that doesn't use sulfuric acid, where toluene/permanganate/water is refluxed for 5 hrs to produce MnO<sub>2</sub> and Potassium benzoate (which is acidified by HCl to produce benzoic acid).

Can someone help clarify this confusion? thanks.:(

<!-- bfesser_edit_tag -->[<a href="u2u.php?action=send&username=bfesser">bfesser</a>: subscript]

[Edited on 3.8.13 by bfesser]
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[*] posted on 13-4-2011 at 13:38


The reaction is probably not very clean at all, but may procede something like this:

14 C<sub>7</sub>H<sub>8</sub> + 154 KMnO<sub>4</sub> --> 77 K<sub>2</sub>CO<sub>3</sub> + 154 MnO<sub>2</sub> + 56 H<sub>2</sub>O + 21 CO

(I am fairly good at balancing ridiculously complicated equations)

<!-- bfesser_edit_tag -->[<a href="u2u.php?action=send&username=bfesser">bfesser</a>: subscript; removed coefficient parentheses; WTF?]

[Edited on 3.8.13 by bfesser]
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[*] posted on 13-4-2011 at 13:50


What the hell are you talking about AndersHoveland? Is this a joke?

Without visualizing it (it helps for me to write things down) I don't know how or why adding H<sub>2</sub>SO<sub>4</sub> would increase the yield of benzoic acid but I really don't think it could hurt. I mean, of course you won't get the salt formation because of it (it will be BnOOH instead of BnOO-Na<sup>+</sup>;).

I'm not sure I even quite understand what's going on here. Are you trying to balance an equation or synthesize benzoic acid?

<!-- bfesser_edit_tag -->[<a href="u2u.php?action=send&username=bfesser">bfesser</a>: subscript/superscript]

[Edited on 3.8.13 by bfesser]
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[*] posted on 13-4-2011 at 14:45


A small ammount of sarcasm was involved, yes. "jamit" was asking for a balanced equation for a reaction in which it is extremely impractical to make any attempt at such ideal equations.

A quick online search suggests that alkaline permanganate can oxidize phenol.
http://docs.google.com/viewer?a=v&q=cache:XS93DI0q_iYJ:a...

If there is excess KMnO<sub>4</sub>, any benzoic acid may likey be oxidized further.
Most of any carbon monoxide that forms is likely to escape from solution before it is oxidized to CO<sub>2</sub>.

<!-- bfesser_edit_tag -->[<a href="u2u.php?action=send&username=bfesser">bfesser</a>: subscript]

[Edited on 3.8.13 by bfesser]
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jamit
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[*] posted on 13-4-2011 at 15:28


it would help if Woelen would reply to what he said in the Scienceforum.net.

Yes I'm trying to make benzoic acid but I would like to understand the reaction better before proceeding with the experiment.
If someone can enlighten me I would appreciate it. thanks.


Woelen!@@ help?
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[*] posted on 2-8-2013 at 12:36


The reaction of potassium permanganate and toluene does not produce benzoic acid. It produces potassium benzoate. The reaction is as follows:

2 C<sub>7</sub>H<sub>8</sub> + 2 KMnO<sub>4</sub> --> 2 C<sub>7</sub>H<sub>5</sub>KO<sub>2</sub> + 2 MnO<sub>2</sub> + 3 H<sub>2</sub>

To obtain benzoic acid from potassium benzoate solution, an acid workup is required. Using hydrochloric acid, the reaction is as follows:

C<sub>7</sub>H<sub>5</sub>KO<sub>2</sub> + HCl --> KCl + C<sub>7</sub>H<sub>6</sub>O<sub>2</sub>

<!-- bfesser_edit_tag -->[<a href="u2u.php?action=send&username=bfesser">bfesser</a>: rxn. eqn. cleanup]

[Edited on 3.8.13 by bfesser]
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[*] posted on 22-2-2014 at 21:18


this is all good, but what I'd like to know is: by what precise mechanism does the potassium permanganate, or the permanganate ion interact with the methyl group to convert so much in aqueous solution into potassium benzoate?

I have also heard that a little sulfuric acid can improve an already pretty good yield. I'm curious whether jamit discovered an adequately credible mechanism.
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[*] posted on 27-2-2014 at 16:25


Quote: Originally posted by IanTWHou  
The reaction of potassium permanganate and toluene does not produce benzoic acid. It produces potassium benzoate. The reaction is as follows:

2 C<sub>7</sub>H<sub>8</sub> + 2 KMnO<sub>4</sub> --> 2 C<sub>7</sub>H<sub>5</sub>KO<sub>2</sub> + 2 MnO<sub>2</sub> + 3 H<sub>2</sub>

To obtain benzoic acid from potassium benzoate solution, an acid workup is required. Using hydrochloric acid, the reaction is as follows:

C<sub>7</sub>H<sub>5</sub>KO<sub>2</sub> + HCl --> KCl + C<sub>7</sub>H<sub>6</sub>O<sub>2</sub>

<!-- bfesser_edit_tag -->[<a href="u2u.php?action=send&username=bfesser">bfesser</a>: rxn. eqn. cleanup]

[Edited on 3.8.13 by bfesser]


You think that hydrogen gas is given off? Not likely.
The actual reaction produces KOH. I know because you can pH test it. You can also leave it the solution and it will absorb CO2. Then add an acid and it will bubble.

The reaction is
toluene + 2 KMnO4 -> potassium benzoate + 2 MnO2 + KOH + H2O




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