garage chemist
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Replacing a phenolic OH-group with chlorine
Does anyone know or can find out if it is possible to replace phenolic hydroxy groups with a chlorine atom using not too exotic reagents?
I have tried this once with thionyl chloride and it definately did not react (mixed ordinary phenol with some SOCl2, boiled for a few minutes,
hydrolysed with water and made basic- everyting dissolved. If it would have worked, chlorobenzene should have been present as oily drops).
Could phosphorus pentachloride work?
I am trying to make o-chlorobenzoic acid from salicylic acid.
If PCl5 could work, I would first turn this into salicylyl chloride using SOCl2 (way cheaper than PCl5) and then replace the OH-group using PCl5.
Any help would be nice.
I tried to make this from anthranilic acid using sandmeyer reaction and it became a disaster (violently erupted as a geyser of foam after about 5
seconds delay after combining the CuCl and diazotised anthranilic acid solutions). Also, anthranilic acid is not very available (cant buy it), making
this failed reaction even more frustrating.
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Nicodem
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The only phenols which can be converted to chlorobenzenes with PCl5 are the ones having heavily electron withdrawing groups ortho/para to the hydroxy
(for example, picric acid is easily converted to 2,4,6-trinitrochlorobenzene with PCl5; a similar thing happens with electron poor heterocycles:
4-hydroxypyridine>4-chloropyridine, etc.). Though your substrate (salicylic acid) does have one electron withdrawing group at the ortho position,
and the intermediate -COCl group is even more electron withdrawing, I think this is probably not enough. Perhaps at certain harsher conditions. I
should check the literature for a certain answer.
Anthranilic acid can not be diazotazed since the diazo intermediate immediately looses CO2 and N2 to form benzyne (which itself immediately reacts
with whatever nucleophile comes nearby first). In fact this is used preparatively (with alkyl nitrites to avoid aqueous media) as the mildest aryne
forming reaction (not requiring strong bases or heat).
PS: Is there a reason why you don't use another synthetic route to o-chlorobenzoic acid? You could chlorinate toluene to a mixture of o- and
p-chlorotoluene (the o- regioisomer generally prevails somewhat) and oxidize to o- and p-chlorobenzoic acids. There must be a solvent for a couple of
recrystallizations to efficiently separate the two.
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
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garage chemist
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Anthranilic acid can definately be diazotised, as I did it and there was NO gas evolution at all.
Maybe we are speaking of different reaction conditions?
Also, I believe Vogel has the preparation of o-chlorobenzoic acid from anthranilic acid specifically by this method (I probably did something wrong
that accounts for the bad runaway, e.g. my CuCl solution was at room temperature and not at 0°C. I used a general procedure for the synthesis of
haloarenes from aromatic amines.).
It would still be very good if salicylic acid can be used as the precursor. I'd be very interested in such a method.
EDIT: o- and p- chlorotoluene are really, really difficult to separate (you need a column with 200 theoretical plates).
Also, I know of no method to separate o- and p- chlorobenzoic acid.
I also want the product to be free from isomers.
[Edited on 28-7-2007 by garage chemist]
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Nicodem
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I checked and I was indeed wrong. The diazotized anthranilic acid does not immediately decompose to benzyne. In fact the zwitterion can actually be
isolated at room temperature, though it can explosively decompose if dry. In solutions it controllably decomposes to benzyne if warmed. More
information on the preparation of benzenediazonium-2-carboxylate and its decomposition to benzyne can be found in http://www.orgsyn.org/orgsyn/pdfs/CV5P0054.pdf
I have not checked if what you said about Vogel containing such a preparation is true, however, for the Sandmeyer reaction I would expect you need to
use methyl anthranilate instead. I see little possibility, even in acidic enough media to protonate the -COO(-) of benzenediazonium-2-carboxylate,
that the intramolecular nucleophilic attack would be avoided and the chloride attack favored. Not even to consider the possibility of Cu(I) catalyzed
decomposition of benzenediazonium-2-carboxylate as a competing reaction trough a SET mechanism.
I was not suggesting to separate the o- and p-chlorotoluenes, though even a partial separation with a less efficient column would certainly help a lot
in separating the chlorobenzoic acids by repeating recrystallizations. I was suggesting exploiting the relatively large solubility differences of the
o- and p-chlorobenzoic acids in order to separate them by doing several recrystallizations. This would certainly drop the overall yield to less than
10% but who cares about yields with precursors like toluene, KMnO4, etc?
Though it depends how extremely free of the p-chlorobenzoic acid you need your product. With this route even after several recrystallizations there
will still be traces of it present. On the other hand if you need a small amount, like 3g or less, you could separate the two with a column.
Edit:
So today I took the time to check the Vogel's preparation of o-chlorobenzoic acid by the Sandmeyer reaction. You were right, it is there (on the page
759 of 3rd edition, just bellow the synthesis of o-chlorobenzoic acid by o-chlorotoluene oxidation). It is a bit unusual in that the chloride
substitution step is done at an ice bath temperature while with other diazonium salts this step is generally done without much temperature control or
even with heating the diazonium solution. Apparently cooling efficiently inhibits the side reactions for which I showed so much exaggerated fear.
Seems like your problem was indeed a reaction runaway. Maybe you could try again with more efficient cooling? Or alternatively try with methyl
anthranilate if available (in our lab we have more of this ester than the acid itself, but I do not know if it so common elsewhere as well). The
hydrolysis of methyl o-chlorobenzoate is as simple as it can get. Or you could just buy pure o-chlorotoluene, given it is so cheap, and just oxidize
it (I would choose to do this if the product is needed in larger amounts).
[Edited on 29/7/2007 by Nicodem]
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
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scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
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garage chemist
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Methyl anthranilate would also be a good precursor, since I initially had only this ester and prepared some of the acid from it. I still have ca.
150ml of the ester.
I wonder how well it will dissolve in HCl? And wouldnt it tend to hydrolyse in this strongly acidic environment?
I suppose the mixing of the diazonium salt solution and the CuCl solution would still have to be done at 0°C and preferrably in a large beaker as a
precaution against overflowing from foam?
Thanks for the help!
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Nicodem
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In that Vogel's diazotation procedure a 20% excess of HCl is used (2.4 eq. HCl over 1 eq. anthranilic acid and 1 eq. NaNO2). Before you start adding
the NaNO2 there is therefore a 120% excess HCl. This makes for a quite acidic environment where hydrolysis could indeed happen, however you have to
consider that this is done in an ice bath, a temperature where even methyl esters hydrolyze very slowly. Unless of course there is some significant
neighbouring group participation from the protonated amine (which is possible, but I would not discard the reaction without trying first). However, if
you are too concerned about hydrolysis you could start with 1.25 eq. HCl and consequently add 0.25 eq. NaNO2 followed by 0.25 eq. of HCl, and
repeating so on until complete diazotation (thus keeping the excess HCl to a minimum throughout the reaction; also rather use a 5% HCl excess instead
of the 20%).
I'm quite sure the hydrochloride of methyl anthranilate dissolves more or less readily in water (aniline hydrochlorides are generally well soluble in
water).
The chloride substitution step should be modified by using NaCl for chloride saturation instead of HCl due to hydrolysis suppression. Since there will
be no need to do the diazonium substitution at 0-5°C you can use much less CuCl than in the Vogel's procedure, but consequently you will have to heat
the solution somewhat (regulate the temperature to such a level as to maintain a controllable N2 evolution; yet due to hydrolysis rather do not
exaggerate since you will still have a somewhat acidic solution). Anyway, I would rather follow another general Sandmeyer procedure than the much
modified one made specificaly for the anthranilic acid (with its temperature bellow 5°C and enormous amounts of copper catalyst).
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
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not_important
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There is a route from the phenol, but it takes less than common reagents.
Reacting the phenol with triphenyl-phosphine dibromide, generated from triphenylphosphine and bromine, at ~200 C will replace the OH with Br. See the
attached, as well as Wiley, Rein, & Hershkowitz Tet. Lett. 2509 (1964), and Schaefer & Higgins, J. Org Chem 32, 1607 (1967)
Another possibility might be making p-toly-sulphonic acid from toluene and H2SO4 at 140 to 160 C, recrystallise to get just the para compound (which
is over 90% of product at those temperatures). Chlorinate that to the 2-Cl, 4-SO3H toluene, then remove the SO3H by boiling with dilute sulfuric acid
+ Na2SO4 at 110 - 120 C or so. Finish off with stock oxidation of the methyl group.
[Edited on 29-7-2007 by not_important]
Attachment: ja01059a073.pdf (284kB)
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garage chemist
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I tried the sandmeyer reaction a second time, now in a 1L beaker (with again 0,1 mol anthranilic acid. I also used only 0,1 mol CuSO4, not the
excessive amounts that Vogel uses).
Despite good cooling this time, the reaction was still nearly instantaneous and immediately filled the whole beaker with foam after only a third of
the diazonium solution had been added. The foam had to be stirred down before the rest of the solution could be added in small portions.
The foam was remarkably viscous and stiff even after the reaction was over and could never be stirred down completely.
The product still has to be filtered and recrystallized.
not_important, that method with triphenylphosphine dibromide sounds very good. Could that work as well with the dichloride?
And why does PCl5 not work?
The method via the sulfonic acid is also elegant since it blocks the para position, giving only the desired isomer.
But how is the sulfonic acid group removed? I dont understand that part. Can you give an example on how a SO3H group is replaced with hydrogen? I have
never come across such a reaction.
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Sergei_Eisenstein
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Sulfonation of the aromatic ring is a microscopically reversible reaction. Take a look at the preparation of ortho-nitroaniline at OrgSyn.
damnant quod non intelligunt
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garage chemist
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Thats interesting, I didnt know that. Thanks! Can desulfonation occur with all aromatic sulfonic acids? Like if I heat PTSA with dilute H2SO4, will
toluene be formed?
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not_important
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| Quote: | Originally posted by garage chemist
Thats interesting, I didnt know that. Thanks! Can desulfonation occur with all aromatic sulfonic acids? Like if I heat PTSA with dilute H2SO4, will
toluene be formed? |
Yes; it can be distilled out of the boiling dilute acid to help force the reaction. It works for many but not all sulfonic acids, the exact
conditions needed vary with the substrate.
As for using chlorine instead of bromine in the replacement of of phenolic OH - I don't know, the other two references I gave may have something on
that. Bromine is a bit easier to work with the chlorine, which may have been the deciding factor in those experiments.
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Nicodem
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Patents on chlorination of p-toluenesulfonic acid: WO9005717, DE286712, DE287932
And the attached paper:
Highly selective oxidative monochlorination to synthesize organic intermediates: 2-chlorotoluene, 2-chloroaniline, 2-chlorophenol, and
2-chloro-4-methylphenol.
Mukhopadhyay, Sudip; Chandnani, Kavita H.; Chandalia, Sampatraj B.
Organic Process Research & Development, 3 (1999) 196–200.
...however, it is more economic to just buy o-chlorotoluene.
Attachment: 2-Chlorotoluene, 2-Chloroaniline, 2-Chlorophenol, and 2-Chloro-4-methylphenol.pdf (41kB)
This file has been downloaded 1890 times
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garage chemist
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Thanks for that paper Nicodem, that is very interesting.
They are however unclear on how the desulphonation was carried out, they say 70% H2SO4 and quinoline as solvent (?) and cuprous oxide as catalyst.
Also 220°C reaction temperature which is impossible with 70% H2SO4.
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Nicodem
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Quinoline with copper catalyst is a general method for ArCOOH decarboxylations and they must have used this in the examples where the protective group
was –COOH (but not for removing the –SO3H group!).
Desulphonations are generally done by refluxing in about 60% H2SO4. In your case this would mean you would be refluxing
4-methyl-3-chlorobenzenesulfonic acid in 60-70% H2SO4 and steam distilling the water/o-chlorotoluene mixture as it forms.
However, contrary to what that paper says, halogenations of compounds where the para position of the activating group is occupied generally leads to
some ipso substitution. I think the –SO3H group should be prone to ipso substitution, however the –Me is not particularly electron donating so
that there should not be much p-chlorotoluene formed. Nevertheless, if your end product must be absuletely free of any para isomer it might be worth
purifying the 4-methyl-3-chlorobenzenesulfonic acid before desulphonation (it should be very easy to remove even traces of p-chlorotoluene by a
variety of methods).
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
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JohnWW
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Thanks, Nicodem. However, Patent WO9005717, at http://v3.espacenet.com/textdoc?DB=EPODOC&IDX=WO9005717&... , is password-protected, preventing it from being viewed or downloaded. Does
anyone have the password for it?
BTW As regards desulfonation, one industrial method for the synthesis of phenol is fusion of sodium benzenesulfonate, C6H6SO3(-)Na(+), with an
aqueous alkali at 300ºC and high pressure, producing sodium phenoxide, C6H5O(-)Na(+), followed by reaction with dilute H2SO4 to produce C6H5OH. This
also works for 2-naphthol and cresols (toluols).
Actually, the major industrial synthetic process for phenol production is the Dow process, which is the reverse of the original purpose of this
thread. Chlorobenzene is reacted with aqueous NaOH at 360ºC and 4,500 psi to produce sodium phenoxide, which is then reacted with HCl solution to
give phenol.
[Edited on 1-8-07 by JohnWW]
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S.C. Wack
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They have something personal against you. Everyone else can view or download it without problems.
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Nicodem
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JohnWW, if for some reasons you have troubles downloading the patent at espacenet then try at WIPO homepage. However, there is no such thing as
password protection at espacenet. That would be absurd given espacenet originated due to the laws about public availability of patent literature.
PS: I fail to see what the production of phenols by fusion of sodium arylsulfonates with NaOH has to do with desulfonation discussed in the posts
above. The fusion with NaOH leaves a phenolate group (–O<sup>-</sup>
and not an –H, so it is not a desulfonation.
[Edited on 1/8/2007 by Nicodem]
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
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manimal
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Quote: Originally posted by garage chemist  | Thanks for that paper Nicodem, that is very interesting.
They are however unclear on how the desulphonation was carried out, they say 70% H2SO4 and quinoline as solvent (?) and cuprous oxide as catalyst.
Also 220°C reaction temperature which is impossible with 70% H2SO4. |
The interesting patent US4091013 tells of simultaneously desulfonating and aminating 1-chloro-4,6-disulphonaphthalene by autoclavical ammonolysis with
a copper catalyst. Perhaps the aforementioned chlorotoluenesulfonate would undergo a similar reaction to form toluidine.
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manimal
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In the old days, iodine was used as a promoter for aromatic sulfonation reactions, increasing yield with a lower acid concentration and decreasing
reaction time. Perhaps it would similarly function as a desulphonation catalyst*, since the ease with which the sulfo group is removed is
proportional to the ease with which it is attached.
*I guess it works to promote sulfonation by p-iodination of the aromatic compound, followed by replacement with a sulfo group, so maybe it would not
work in this capacity.
| Quote: |
J. Chem. Soc. 117, 1405-1407 (1920):
The Catalytic Action of Iodine in Sulphonation. Part I
By Jnanendra Nath Rây and Manik Lal Dey
The present investigation was undertaken with the view of ascertaining whether the addition of a trace of iodine to sulphuric acid (D 1.84)
facilitates the sulphonation of aromatic compounds (compare Heinemann, Brit. pat 12660 of 1915 (Patent GB191512660)). It has been found that ordinary
sulphuric acid and a trace of iodine can be advantageously used in place of fuming sulphuric acid with or without the addition of phosphoric oxide,
etc. The nature of the product is changed in certain cases, thus making easy the preparation of some of the acids difficult to obtain. The catalytic
sulphonation is facilitated by the presence of an amino-, hydroxy-, or halogen group in the molecule, but proceeds with less ease in the case of
carboxylic acids, and is inhibited in the case of nitro-compounds. This fact probably explains the non-formation of disulphonic acids in the product.
It is significant that there is an optimum temperature for each reaction in which maximum transformation takes place. It has also been noticed that
there is some liberation of iodine vapour, but no trace of sulphur dioxide or hydrogen iodide could be detected in the space above the reaction
mixture.
The discrepancy between the actual yield and that theoretically possible was accounted for in nearly all cases by the unchanged original
material.
Experimental
In the experiments to be described below, the general method of work was to heat a mixture of a few grams of the substance and the calculated
quantity, or an excess, of sulphuric acid (D 1.84), together with a trace of iodine, for a few hours at the temperature, determined by trial, at which
the transformation was greatest. The product was poured into water, the free sulphuric acid removed with barium carbonate or hydroxide, and the acid
liberated from the filtrate by exactly neutralising with sulphuric acid. The solution of the free acid was concentrated, whereupon it was obtained in
a crystalline condition. In some cases the product was poured into a saturated solution of potassium chloride, when the potassium salt separated in
fine crystals (o-nitrophenol, etc.). The acid of the potassium salt was converted by the usual method into the sulphonyl chloride from which the
amide, mercaptan, etc., were prepared in order to characterise it. Some of the sulphonic acids described gave colour reactions with ferric chloride
and characteristic salts with heavy metals. When the acid could not be satisfactorily identified, it was transformed through its amino- or
nitro-groups, etc., into the corresponding hydroxy- or amido-compounds, etc., in order to establish its constitution. In some cases it was found
convenient to extract the sulphonic acid from the sulphonated mass with alcohol (o-toluidine).
The results obtained from the fusion of the products with potassium hydroxide were not taken into account unless substantiated by further
evidence.
Sulphonation of Benzoic Acid
A mixture of 12 grams of benzoic acid, 9 c.c. of sulphuric acid, and a small crystal of iodine was heated at 175-180° for about six hours, at
the end of which time no free benzoic acid separated on diluting a sample. The liquid, after cooling, was poured into water, when a clear solution was
obtained. The solution was neutralised with barium carbonate, the precipitated barium sulphate filtered off, and the filtrate exactly neutralised with
dilute sulphuric acid. After filtering, the liquid was concentrated to a syrup, and, on keeping in a dessicator, crystals were obtained, which were
drained, washed with a small quantity of alcohol, and dried over sulphuric acid in a vacuum. The anhydrous crystals melted at 134-135° (uncorr.), and
were hygroscopic.
A test experiment was conducted side by side with the above in which no iodine was used; almost the whole of the benzoic acid was recovered
unchanged.
The crystals in aqueous solution gave a reddish-brown coloration with ferric chloride, but no precipitate, and were identified as
o-sulphobenzoic acid by the formation of salicylic acid when fused with potassium hydroxide at a moderately low temperature (Found: S=15.0 per cent.
Calc for acid + 1H2O: S=14,57 per cent.).
In the above experiment a gram of benzoic acid sublimed away, and was thus not sulphonated.
The following table gives a résumé of the results obtained with other substances:
[Table unavailable. Says basically that increased yields are realized from most aromatics, and toluene is sulfonated to yield exclusively p-isomer.]
Summary and Conclusions.
(1) Iodine acts as a positive catalyst in sulphonation.
(2) Catalysis takes place smoothly when hydroxy-, amino-, chloro-, bromo-, or carboxy-groups are contained in the molecule, but with
difficulty, or not at all, with nitro- or sulphonic.
(3) There is an optimum temperature for each substance when the maximum temperature takes place.
We have much pleasure in according our best thanks to Sir P.C. Rây for the interest he has taken in the work.
College of Science, University of Calcutta. [Received, January 28th, 1920.]
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[Edited on 18-12-2009 by manimal]
[Edited on 18-12-2009 by manimal]
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manimal
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| Quote: Originally posted by manimal | I guess it works to promote sulfonation by p-iodination of the aromatic compound, followed by replacement with a sulfo group...
[Edited on 18-12-2009 by manimal] |
No, that cannot be. The former is a redox reaction, while sulfonation is a metathesis reaction. I need to flesh this out...
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CuReUS
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according to March,PhPCl4 has to be used for chloro
https://books.google.co.in/books?id=4zrovKbIxOIC&pg=PA65...
| Quote: | | And why does PCl5 not work? |
because phenols form phosphates,similarly friedel craft reaction with phenols give poor yield as the -OH will complex with AlCl3,also
reimer- tiemann reaction gives poor yields(less than 50%) due to this property of -OH group
http://www.thestudentroom.co.uk/showthread.php?t=1986289&...
https://in.answers.yahoo.com/question/index?qid=201307312027...
| Quote: | | But how is the sulfonic acid group removed? I dont understand that part. Can you give an example on how a SO3H group is replaced with hydrogen? I have
never come across such a reaction. |
SO3H can be replaced with H easily with raney nickel
[Edited on 5-1-2015 by CuReUS]
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UC235
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Reimer-Tiemann has absolutely nothing to do with the friedel-crafts alkylation.
The Reimer-Tiemann ONLY works on phenols and is performed in aqueous base without a trace of lewis acid present. Poor yield is the
product of numerous side reactions. Despite a very large excess of chloroform, there is always some unconverted phenol recovered. A significant
fraction of the product is the para-product which is lost/separated from the salicylaldehyde by typical steam distillation during workup. The
intermediate o/p-(dichloromethyl)phenol and/or the aldehyde can react with further equivalents of phenol/phenoxide, resulting in aurins
(triarylmethane derivatives). I suspect that a significant amount of typical organic polymeric tar forms as well from air oxidation (which phenoxide
is very susceptible to). Lastly, the Cannizzaro reaction more than likely destroys a significant amount of the product.
With larger, more hindered structure and under precise conditions, tolerable yield can be achieved. See http://www.orgsyn.org/Content/pdfs/procedures/cv3p0463.pdf
For the original reaction, see attached.
[Edited on 6-1-2015 by UC235]
Attachment: ReimerTiemannreview.pdf (1.4MB)
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CuReUS
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I never said RT is friedel craft or that it it done in the presence of lewis acid. I said that many reactions like PCl5, RT,FC etc did not
give good yields with phenol due to the property of phenol to convert to phenoxide so easily
like you said,the dichloromethyl intermediate formed will react with 2 moles of phenoxide and when you hydrolyse the product you get one mole of
aldehyde and 2 moles of unreacted phenol
but you are saying that a significant fraction is para.This is interesting ,could you tell the ortho:para percentage please ?
| Quote: | | The Reimer-Tiemann ONLY works on phenols |
It also works on heterocyclic compounds like thiophene,pyrrole and indole
[Edited on 7-1-2015 by CuReUS]
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UC235
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See table 1 on page 172 of the reimer tiemann review I attached above for o:p ratios. It seems to vary with NaOH concentration.
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