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Chlorination of aromatic compounds with bleach
Is it possible to chlorinate carboxylic acid salts (benzoic or acetic salts) or phenol with hypochlorite?
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Bot0nist
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Is <a href="http://www.erowid.org/archive/rhodium/chemistry/5-chlorovanillin.hypochlorite.html">this</a> what you are referring to?
This link may also be relevant. http://www.springerlink.com/content/w057238166q71746/
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bbartlog
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I don't think you can chlorinate acetic salts this way, but phenolic compounds including salicylic acid and phenol can be chlorinated via
hypochlorite. You would have to research the appropriate conditions... having chlorinated aqueous salicylic acid (somewhat by accident, was trying to
do something else) I believe that alkaline conditions and/or air exposure will tend to get you oxidized rather than chlorinated derivatives, at least
as a side reaction. Thus you would sort of want acid conditions, but then the hypochlorite will gas off chlorine. Thus dripping the hypochlorite
solution into a well-stirred acidic solution of your phenolic substrate seems like the best bet to me (either that or a thistle tube)... but in any
case, just do some reading, I remember finding lots of references when I look into salicylic acid plus hypochlorite.
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Could phenol be chlorinated to 2,4,6-TCP?
So, the reaction is possible, but I need to be careful to not produce too much chlorine. I will check for salicylic acid chlorination.
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smuv
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yes
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I found this:
http://www.nature.com/nature/journal/v131/n3297/abs/131028d0...
This means that the reaction of alkaline sodium hypochlorite with sodium benzoate produces meta, para and ortho isomer sodium salts of chlorobenzoic
acids. Addition of HCl to these salts should precipitate hydroxybenzoic acids (like sodium monochloroacetate + HCl makes glyoxylic acid). Those
hydroxybenzoic acids can be decarboxylated to phenol, a lot easier than sodium benzoate -> benzene -> aniline route. Maybe there are a lot more
uses to hydroxybenzoic acids, but I don't know currently.
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bbartlog
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| Quote: | | Addition of HCl to these salts should precipitate hydroxybenzoic acids (like sodium monochloroacetate + HCl makes glyoxylic acid).
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You sure about any of that? I would expect sodium monochloroacetate plus HCl to give NaCl plus chloroacetic acid. Now I suppose that chloroacetic acid
plus KOH or NaOH might, under the right conditions, give you glycolic acid... but anyway as regards the chlorinated benzoic acid, replacing the Cl
with an OH sounds like something that would require fusion with caustic potash, not addition of HCl.
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Random
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Here is written on wikipedia: http://en.wikipedia.org/wiki/Glycolic_acid
It is prepared by the reaction of chloroacetic acid with sodium hydroxide followed by re-acidification. The net reaction can be summarized as follows:
ClCH2CO2H + NaOH → HOCH2CO2H + NaCl
In this way, a few million kilograms are produced annually.
Here we have salts of them, just now they have to be re-acidified.
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bbartlog
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Yes, that's the net reaction... but:
- note that glycolic acid and glyoxilic acid are not the same thing
- the reaction seems likely to involve first using two equivalents of NaOH - one to form the sodium salt of chloroacetic acid and a second to then
remove the chlorine atom. So it is not going to be 'sodium monochloroacetate + HCl', rather it seems like you would first need sodium chloroacetate
plus sodium hydroxide to form sodium chloride and the sodium salt of glycolic acid, *then* acidify to free glycolic acid. Now I could be wrong and
maybe sodium chloroacetate can somehow react with itself under forcing conditions to give you NaCl plus the free glycolic acid, but still no HCl is
involved in that reaction, and anyway if that were the case then why would reacidification be required?
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GreenD
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"32 per cent meta" interesting read!
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Yes, I written by mistake glyoxilic acid instead of glycolic acid. Actually, to the mixture of sodium chlorobenzoates needs to be added NaOH to make
hydroxybenzoates and NaCl. Then it needs to be reacidified to make insoluble hydroxybenzoic acids. Those can be heated with Ca(OH)2 to decarboxylate
them and phenol should still react with excess Ca(OH)2 to make phenoxide salt or a part of the phenol would be distilled.
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