So I was running an IR on a sample that I had thought (or rather hoped) was phenol (hydroxy benzene), but what came out was either trash and noise, or I simply did not have phenol. My professor and I were quite stunned as it showed no signs of organic peaks at all, especially no -OH peak near 3100. My professor suggested to run my reaction again, but sadly I do not have the reagents on hand at the moment and it will be some time before I get them.
The reaction I ran was one taken from an old book on recycling benzene waste. When I conducted it, I took a mixture of nitrobenzene and benzene waste and I added a random amount of relatively pure Fe2O3 and 13% Hydrogen Peroxide to try and oxidize anything in the waste to phenol or hydroxynitrobenzene. After I treated it with NaOH to make a phenoxide salt and then I did some work up to isolate. What I was left with was a nice white crystalline salt (or so I thought). But the IR says it contains zero organics as far as our IR machine can tell, and our machine is used daily if not hourly, and is kept in great condition.
If someone could help me understand what I have or teach/lead me how to identify inorganics, that would be very appreciated.
Because the attached picture is possibly hard to see small details, I have listed the peaks as well.
Peaks:
-610.07 cm^-1 transmittance: 60%
-635.08 cm^-1 transmittance: 79%
-1091.13 cm^-1 transmittance: 64/65%
Rizal Awaludin Malik After rereading my notes, I have come to realize that I distinctly changed my procedure because I was having trouble with the Iron Oxides previously mentioned. My pseudo-procedure looks more like this:
Fe + 2HCl -> FeCl2 + H2
2FeCl2 + Cl2 -> 2FeCl3
FeCl3 + H2O2 (13% aq) -> Fe(OH)3 + Reactive Species
And my idea was to combine the benzene/nitrobenzene wastes I had with the final reaction in the scheme (combining the reactive species) to try and produce hydroxylated benzene and nitrobenzene.
Some notes from my notebook leave me further puzzled:
"Smell of nitrobenzene and benzene has totally disappeared, and lots of gas evolution. A red precipitate (likely iron oxides) has formed at the bottom of the beaker. There is no longer 2 layers (2 phases) and the yellow color of the solution is very faint, where it was quite deeply colored beforehand."
I'm not sure what exactly happened but I have done a little bit of searching and came across Hexaaqua iron (III) chloride, which may be what I have crystallized out.
To explain further, after the whole reaction was completed, I filtered off the red precipitate and tried to crystallize out whatever product I had formed. When I did so, I was left with a pure white free-flowing powder. The powder seems hygroscopic in nature.
I will likely try this again, with pure benzene to see if the same result occurs.
Hi Aidan,
after reading your description about the problem, i think the problem is the mixture of Fe2O3 and peroxide which perhaps triggering Hydroxil radicals (fenton process)which will oxidizing your sample and probably lead to mineralization so there would be no organics left in your sample, try to reduce your Fe and peroxide and see what happend. I've been using fenton (FeSO4 & H2O2) for dyes decolorization and even in small amount it could oxidize or even mineralized the dyes.
Oh, and also i think you need to read the IR spectra of the mixture without Fe2O3 and H2O2 to make sure your protocol is not the problem.
Regards
Rizal Awaludin Malik After rereading my notes, I have come to realize that I distinctly changed my procedure because I was having trouble with the Iron Oxides previously mentioned. My pseudo-procedure looks more like this:
Fe + 2HCl -> FeCl2 + H2
2FeCl2 + Cl2 -> 2FeCl3
FeCl3 + H2O2 (13% aq) -> Fe(OH)3 + Reactive Species
And my idea was to combine the benzene/nitrobenzene wastes I had with the final reaction in the scheme (combining the reactive species) to try and produce hydroxylated benzene and nitrobenzene.
Some notes from my notebook leave me further puzzled:
"Smell of nitrobenzene and benzene has totally disappeared, and lots of gas evolution. A red precipitate (likely iron oxides) has formed at the bottom of the beaker. There is no longer 2 layers (2 phases) and the yellow color of the solution is very faint, where it was quite deeply colored beforehand."
I'm not sure what exactly happened but I have done a little bit of searching and came across Hexaaqua iron (III) chloride, which may be what I have crystallized out. But then again, this is just a weak guess.
I was not able to determine the identity of the gas that was released from the solution. I wonder if it was CO2 that was formed from the violent breakdown of the aromatics, which would be one possible explanation for the disappearance of the distinct nitro yellow color. This is as you suggested, Fenton's process.
To explain further, after the whole reaction was completed, I filtered off the red precipitate and tried to crystallize out whatever product I had formed. When I did so, I was left with a pure white free-flowing powder. The powder seems hygroscopic in nature.
I will likely try this again, with pure benzene to see if the same result occurs.
Article Enhanced degradation of gaseous benzene by a Fenton reaction
Aidan Bradley as we know the range 1085-1050cm-1 is for strong C-O stretching. This is a primary alcohol. You have a pick is the 1091.13 cm-1 so it is more likely that is indicating the presence of C-O stretching. The other two picks are 636.06cm-1 and 610.07 cm-1. We know 690-515 cm-1 range indicates the presence of strong C-Br stretching, which is a halo compound. So those two picks are indicating the presence of C-Br stretching.
For the reference you can check the link below:
https://chem.libretexts.org/Ancillary_Materials/Reference/Reference_Tables/Spectroscopic_Parameters/Infrared_Spectroscopy_Absorption_Table
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