I have made quite a few organic nitrites recently, simply by mixing a cold solution of NaNO2 and an alcohol (e.g. CH3CH2CHOH or CH3CH(OH)CH3 or CH3OH)
and then adding cold dilute H2SO4. The ester separates as pale yellow liquid, or bubbles out of solution as gas.
Now I tried to do this with phenol. I dissolved some pure crystalline colorless phenol in water. This at first is a milky liquid, but after a while a
colorless solution is obtained, containing around 10% phenol (not measured, just estimated, based on amount of phenol and added amount of water). To
this, I added some solid NaNO2. The NaNO2 easily dissolves and does not seem to react. The resulting solution is clear and colorless.
Next, I added a few drops of dilute H2SO4. When this is done, then at once, the liquid becomes turbid and red/brown. No gas is produced. I added a
little more dilute H2SO4. When this is done, then the liquid becomes very dark brown, and some oily nearly black stuff sticks to the glass and to the
surface of the liquid. Again no gas is produced. The liquid does not become warm.
The oily stuff is really nasty, it smears everything which comes in contact with it. A glass stick immersed in the liquid and drawn back becomes
really dirty, covered with an irregular film of red/brown oily material.
The material also seems to be air-sensitive. In contact with air, the oily stuff rapidly darkens to very dark green/grey.
I added a lot of excess NaOH to the liquid. When this is done, then the liquid becomes hot (as expected, due to the reaction between excess H2SO4 and
NaOH) and the oily stuff dissolves and the liquid becomes clear and intensely dark green. Fortunately, in this way I was able to clean the stained and
smeared glass.
The smell of the oily material was not really strong, it was similar to the smell of phenol itself, albeit a little bit more spicey. Not knowing the
toxicity of the material I was careful smelling it, so I only smelled it very briefly.
This was just a little tryout and I just wondered whether phenol is capable of forming nitrite-esters, like C6H5ONO, but apparently it cannot. I also
certainly did not get C6H5NO2, which is a pale yellow liquid with a very strong almond-like odour. DJF90 - 22-10-2013 at 04:32
Phenol can be nitrosated under these conditions, giving the 4-nitrosophenol. Theres a write up at VC by Christiankmno4 - 22-10-2013 at 04:47
Phenol can be nitrosated under these conditions, giving the 4-nitrosophenol. Theres a write up at VC by Christian
This reaction is far more complicated (unfortunately) and results very strongly depends on conditions.
Some 2-nitrosophenol is also present, additionaly phenol condensates with nitroso derivative... -> very impure product "4-nitrosophenol".
If pure, it forms slightly yellow crystals (ex. DOI: 10.1002/recl.19500690409).
Also: http://www.sciencemadness.org/talk/viewthread.php?tid=12677#... papaya - 22-10-2013 at 05:16
I'll be very much indebted if someone explains me why very dilute cold nitrous acids(nitrite + acid) forms esters with alcohols so easily, while to
form nitrates one needs strong HNO3 + H2SO4 ! Boffis - 27-10-2013 at 09:05
@ Woelon
Try the experiment at about 0C and you should get the 4-nitrosophenol on good yield. p-cresol also works well though the yield in low; the 2-nitroso
cresol is an interesting chelating agent. I have carried out this reaction with 2-naphthol, resorcinol and phloroglucinol and low temperatures are
very important to limit the tar formation and the yield seems to fall with increasing number of OH groups. The preparations of naphthol derivative is
described in Vogel's Textbook of organic chemistry 3rd ed, and various books on dye intermediates and the two later in Urbanski Vol 1 where they are
intermediates in the preparation of the corresponding trinitro compound.
In summary the secret appears to be dilute solutions, low temperatures and stoichiometric quantities.PHILOU Zrealone - 30-10-2013 at 07:53
Nitrosation happens very fast in phenol type molecules...usually in para position to the hydroxy group.
The p-nitrosophenol is also subject to molecular resonance and proton jump into a quinonoid form (quinon monoxime).
HO-C6H4-N=O <==> O=C6H4=N-OH
Alcohols are easily subjected to esterification by HONO (or NO(+)) to make nitrous esters because the reaction speed is very fast (much faster than
with HONO2 or NO2(+)) but it is also very reversible! Thus the reversal reaction of nitrous esters in presence of water displays fast hydrolysis. The
speed of reaction in both sides is considered to be almost instantaneous.
Most nitrous esters are volatile and isolable by distillation. The first members are even gaseous and as such are expelled from the system...what is a
motor to push the reaction to go on that side of the equilibrium.
Nitrous esters are flamable and may be explosive.
Nitrous esters are isomeric with nitroalcanes but nitroalcanes are stabler and so the heat of combustion of nitrous esters is slighly higher than
related nitroalcanes...
Nitroalcanes are much denser than nitrous esters... so nitroalcanes display better volumetric explosive performances than related nitrite esters.
There exist an isomerisation temperature to pass from nitrite ester to related nitroalcane (in the range of 120°C); but slightly above that
temperature, you find the exothermic decomposition temperature of nitrite esters into aldehydes, carboxylic acids...
There is also a crossed reaction between nitroalcane and nitrous ester to make nitrosonitroalcanes and alcohol.
CH3-CH2-ONO --> CH3-CH2-NO2
CH3-CH2-ONO + CH3-CH2-NO2 --> CH3-CH(-N=O)-NO2 + CH3-CH2-OH
CH3-CH(-N=O)-NO2 <==> CH3-C(-NO2)=N-OH
So in the mix from ethyl nitrite you would get nitroethane, ethyl nitrite ester, nitrosonitroethane, ethanal, ethanoic acid, glyoxylic acid, oxalic
acid, nitromethane, formol, formic acid, carboxylic acid and condensation products between aldehydes and nitroalcanes (nitroalcohols and nitroalcenes
via Henry reactions).
[Edited on 30-10-2013 by PHILOU Zrealone]DraconicAcid - 30-10-2013 at 13:09
Nitrosation happens very fast in phenol type molecules...usually in para position to the hydroxy group.
The p-nitrosophenol is also subject to molecular resonance and proton jump into a quinonoid form (quinon monoxime).
HO-C6H4-N=O <==> O=C6H4=N-OH
Nit-pick. This is not resonance, but tautomerism.Boffis - 8-5-2014 at 08:23
I recently prepared some trinitrosophloroglucinol by the same method I usually use for some experiments with transition metal complexes. This time I
decided to recrystallize the initial light brownish product from isopropanol and water (50:50). I stirred the initial nitroso compound into a small
volume of solvent and began warming it to 70 C adding more solvent until all the solid had dissolved giving a dark brown solution. To my surprise on
cooling a black, microcrystalline precipitate formed that resembles charcoal. The material is sparingly soluble in water but soluble is alcohols, it
still give the intense green colouration with ferric ions, it decomposes suddenly without melting when heated. The initial material is a light
yellowish brown, light weight granular material resembling biscuit crumbs or sand.
Does anyone have any idea what might have happened?
