In continuation to my earlier posting, I again tried this Condensation step converting my arylaldehyde to its nitroethanol derivative with some other
route.
Recently I came across one US patent in which aldehyde was being converted to its bisulphite adduct using sodium bisulphite & then it was
condensed with separately prepared sodium salt of nitromethane (prepared from dissolving nitromethane in eq. molar NaOH aq. solution).
But when I tried this procedure, after the condensation, I got my aldehyde back from that reaction mixture !! Here, I think after addition of Na-Nitromethane solution, the adduct breaks down again to the aldehyde due to
alkalinity.... Is it so ?
I had also attached copy of that USP for your ready reference.
Here, I must say, this process is a nice route for me (if it works !) because as my reactant arylaldehyde is having OH group & it can be only
converted to its nitroethanol derivative by first protecting this OH group by acetylating it & then condensing. But by this process, I may
directly convert the OH-aldehyde to its OH-nitroethanol derivative.
Please try to understand my problem carefully & suggest me some solution for doing this task !!
Regards,
Kamal
[Edited on 9-6-2006 by kamal]
Attachment: US2151517A1.pdf (209kB) This file has been downloaded 1480 times
Method of Jonas Kamlet
kamal - 13-6-2006 at 19:08
Still awaiting for your suggetions, friends !
Any ways, I again try to get your attention.......
I tried method of Jonas Kamlet (USP2151517) for making 3-hydroxyphenyl-2-Nitroethnol, as attached in my earlier posting. But I could not get the
conversion at all ! I don't know where I'm mistaking.
According to this, I reacted bisulphite adduct of m-Hydroxy benzldehyde with sodium salt of nitromethane in aqueous media. But without/with heating, I
did not get my aldehyde converted to it Nitroethanol derivative at all.
Friends, pls try to suggest me, if I have to add something else to initiate this reaction or to alter something.......
Awaiting...................................kmorendha Nicodem - 14-6-2006 at 00:28
I don't have the will to read that patent, but from what you described I would assume your reaction media is not basic enough to allow for a Henry
condensation. Mind that if the only source of base is the nitronate salt it is quite likely that it gets neutralized soon after the addition to the
bisulphite adduct as this is decomposed quite rapidly to the not so basic SO3(2-). Additionally, your substrate is a phenol, thus relatively acidic,
which additionally works against maintaining a basic enough pH by merely using the nitronate. Perhaps you should check the pH of the reaction mixture
after the nitronate addition. If it is bellow 10 to 11 you should add some additional base (KOH, K3PO4, NaOH or K2CO3) to raise it somewhat, but not
too much or else all of the phenol will get deprotonated (the deprotonated form of any hydroxybenzaldehyde is always way less electrophilic than the
non deprotonated form, though this effect is least expressed in the meta-hydroxybenzaldehydes). Check the pKa(H2O) values to understand better where
the problem lies:
MeNO2 10.2
H2SO3 1.9
HSO3(-) 7
m-hydroxybenzaldehyde 8
(the bisulphite adduct probably has a pKa similar to other sulphonic acids, that is <2)
PS: Patents are a good source of information on various procedures but the authors often don’t take enough care to make their procedures
reproducible (their intention is to merely legally protect industrial use). You can even find many funny hoaxes in the patent literature, since the
applied patents are not checked for validity. In general patents are a weird hybrid between technology and law, so you better take their claims with
some reserve.turd - 14-6-2006 at 09:10
Quote:
Originally posted by Nicodem
I don't have the will to read that patent, but from what you described I would assume your reaction media is not basic enough to allow for a Henry
condensation.
Note that kamal doesn't want a condensation reaction, but rather only addition of the MeNO2.
Condensation
kamal - 14-6-2006 at 19:50
No turd ! Nicodem is right. I want the condensation between my aldehyde & nitromethane making its nitroethanol derivative.
Nicodem, I checked the pH of the reaction after ading nitromethane salt to the aldehyde adduct & it was around 8.5 ! So I think your suggetion
seems to be right to raise the pH.
I'm trying now making the media basic & will run the reaction accordingly as you suggested. Will inform my results soon on the forum.
Thanks a lot for the suggetions...!
kamal Nicodem - 14-6-2006 at 23:32
Quote:
Originally posted by kamal
No turd ! Nicodem is right. I want the condensation between my aldehyde & nitromethane making its nitroethanol derivative.
Well, actually Turd is formally correct in saying that it is not a condensation. A condensation is defined as a reaction where two molecules bind with
the elimination of a considerably smaller molecule (usually H2O). The usual Henry reaction is normally an addition of the nitronate nucleophile on the double bond of the carbonyl group in an aldehyde/ketone (without H2O
elimination). It can also be a condensation if in the next step the water eliminates as it often happens with the benzaldehydes under certain
conditions.
In my reply I considered that what you want is a nitroetanol, but since I’m more accustomed to the “Henry condensation” I made the mistake of
calling your reaction this way. But I think Turd knows where this confusion comes from. transformer - 15-6-2006 at 01:46
Alternativeley you could also consider to try a tertiary amine as a condensation catalyst triethylamine for example.
Here, I think after addition of Na-Nitromethane solution, the adduct breaks down again to the aldehyde due to
alkalinity.... Is it so ? 
