04-15-03 11:25
No 426905
I'm in desperate need of help with balancing a reaction.
Na2S2O6 + -NO2 + 6 H+ --> Na ??? + -NH2 + 2H2O
I have no idea what the oxidation products are therefore I'm stuck.
Help
Freaky
(Hive Addict)
04-15-03 12:00
No 426908
Na2S2O6 + 2 RNO2 + 10H+ --> 2 NaHSO4 + 2 RNH2 + 2 H2O
As dithionites are oxidized to hydrogensulfites, I thought that dithionates might be oxidized to hydrogensulfates.
The faster you run, the quicker you die.
(Hive Bee)
04-15-03 12:10
No 426909
The reduction half reaction is:
R-NO2 + 6 H+ + 6 e- __> R-NH2 + 2 H2O
The oxidation half reaction is:
S2O62- + 2 H2O __> 2 SO42- + 4H+ + 2 e-
Hence, the total reaction is:
R-NO2 + 3 S2O62- + 4 H2O __> R-NH2 + 6 SO42- + 6 H+
EDIT: GC_MS, you got to it first. You're right: NaHSO4 will bee the product (screwed up the oxidation half reaction, lost track of the damned sodium ions LOL
)Then the oxidation half reaction should be:
Na2S2O6 + 2 H2O __> 2 NaHSO4 + 2 H+ + 2 e-
By multiplying the oxidation half reaction by three and adding it to the reduction half reaction, we obtain:
R-NO2 + 3 Na2S2O6 + 4 H2O __> R-NH2 + 6 NaHSO4
(Hive Bee)
04-15-03 12:59
No 426910
Megatherium is a bit confused over here ... the mass balances of both equations seem to bee correct ...
GC_MS: Na2S2O6 + 2 RNO2 + 10H+ --> 2 NaHSO4 + 2 RNH2 + 2 H2O
Mega : R-NO2 + 3 Na2S2O6 + 4 H2O --> R-NH2 + 6 NaHSO4
Is Megatherium doing too many drugs & is he losing his mind ?
HELP ...
(Hive Addict)
04-15-03 13:17
No 426915
GC_MS has 10 positive charges on the left, but none on the right!?
that isn't ok, is it?
(Hive Bee)
04-15-03 13:53
No 426929
Indeed, you 're right: it isn't.
3 x (Na2S2O6 + 2 H2O --> 2 NaHSO4 + 2 H+ + 2 e-) (ox)
R-NO2 + 6 H+ + 6 e- --> R-NH2 + 2 H2O (red)
What is nice here is that the reaction seems to be auto-catalyzed: the protons that are created in the oxidation are used in the reduction. However, I think the addition of some acid (1 eq. during the reactiton) would be required since: R-NH2 + H+ --> R-NH3+
Oeff, what a relief: I can continue with my old habits
(Hive Addict)
04-15-03 14:05
No 426931
I mistook dithionate S2O62- for dithionite S2O42-. Feeling really silly
Dithionite is the reducing agent I'm curious about. But what is the oxidation product?
Bisulfate, HSO4- or
Sulfate, SO42-
Freaky
(Hive Addict)
04-15-03 14:29
No 426935
Oeff, what a relief: I can continue with my old habits
Yes, recalculated after hypo said my ion balance was way out. Have something like 2 S2O62- + 4 H2O + RNO2 --> 6 HSO4- + RNH2
Shit, and that while wasn't on my drugs... 
The faster you run, the quicker you die.
(Hive Bee)
04-15-03 16:53
No 426962
when dithionite is oxidised by Fe3+ or CrO42-the oxidation product is SO32- (sulfite)
not sure what the oxidation product is when reducing nitro groups tho'.
(Hive Bee)
04-15-03 17:52
No 426978
Dithionite is the reducing agent I'm curious about. But what is the oxidation product?
Bisulfate, HSO4- or
Sulfate, SO42-
When dithionite is oxidised by Fe3+ or CrO42-the oxidation product is SO32- (sulfite)
not sure what the oxidation product is when reducing nitro groups tho'.
It seems indeed more reasonable to expect that the oxidation product here will be SO32- instead of SO42- or HSO4-.
I can't imagine that R-NO2 would be a better oxidant than CrO42-, and has the power to oxidate the sulfur from Na2S2O4 to an oxidation state +VI (like in SO42-). It is indeed pretty sure that the oxidation state from the sulfur in dithionite will change from +III to +IV in the oxidation half reaction.
Hence, we get for the oxidation half reaction:
S2O42- + 2 H20 --> 2 SO32- + 4 H+ + 2 e-
The reduction half reaction remains the same (cfr supra), so after multiplying the oxidation half reaction by three and adding it to the reduction half reaction, we obtain:
R-NO2 + 3 S2O42- + 4 H20 --> R-NH2 + 6 SO 32- + 6 H+, which can be rewritten as:
R-NO2 + 3 Na2S2O42- + 4 H20 --> R-NH2 + 6 NaHSO 3
OK, enough redox chemistry for today already. Now, its time for a good joint
.
(Hive Addict)
04-15-03 19:03
No 426986
This will hopefully be very beneficial to all of us. Just give me some time to get dirty in the lab
Freaky
(Hive Bee)
04-15-03 19:53
No 427000
No prob. Are you going to reduce a aryl-2-nitropropane with the Na2S2O4? That would bee rather cool
.
(Hive Addict)
04-16-03 10:30
No 427207
Naaaaaah, no way he is going to try that cheap OTC product on nitroalkanes
Might be nice thing if it worked. It works for phenyl-1-propanone -> phenyl-1-propanol.
The faster you run, the quicker you die.