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nightflight
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Carboxylic acid -> Alkan
Hi,
I was intersted in how to perform this best, with not so expensive catalysts and good yields.
So what I cam came across to synthesize an alkane from a aninoaryl-CO2H was:
I. Reacting the carboxyclic acid with thionyl chloride to yield a
chlorocarboxylic acid.
II. Catalytic reduction of halide to yield a hydrogen, resp. aldehyde (Aluminiumamalgam?)
II. Clemmens reduction of the Aldehyde to get the alkane, by heating with Zn(Hg) in HCL.
What do you think about the Barton decarboxylation mentioned in this paper: http://www.chem.harvard.edu/groups/myers/handouts/1_Reductio...
?
Reacting an ester of N-hydroxy-2-thiopyridine with a tin-hydride catalyst -unfortunately not much is stated about the selectivity of this
decarboylation.
Intresting would be Vogel´s synthsis of (S)-2-Amino-3-phenylpropan-1-ol, by reaction phenylalanine to the ethylester*hcl in EtOH and SOCL2 successive
reduction in high yield by Sodiumborohydride and subsequent deoxygenation of the alcohol, by the Mitsunobu displacement, wouldn´t it?
[Edited on 18-3-2007 by nightflight]
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garage chemist
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Caboxylic acid to the alkane can be done directly in one step with red P and hydroiodic acid. Look in the old Gattermann (Sciencemadness library),
theres a preparation of diphenylmethane from benzophenone in there that uses this method. It is stated there that HI/P reduces all oxygen compounds
like alcohols, aldehydes and carboxylic acids, to the alkane.
[Edited on 18-3-2007 by garage chemist]
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nightflight
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Oh cool, thanks I ´ll look that up, after like spending 3 days of searching and learning the above mentioned stuff.
[Edited on 18-3-2007 by nightflight]
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solo
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| Quote: | Originally posted by garage chemist
Caboxylic acid to the alkane can be done directly in one step with red P and hydroiodic acid. Look in the old Vogel (Sciencemadness library), theres a
preparation of diphenylmethane from benzophenone in there that uses this method. It is stated there that HI/P reduces all oxygen compounds like
alcohols, aldehydes and carboxylic acids, to the alkane. |
I apologize for my question but I wasn't able to locate the preparation of diphenylmethane using the RP/HI......would it be possible to give the page
#....thanks,......solo
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nightflight
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But why is it so hard to find? all I see is reductions to alcohol, using various metal catalysts or the hunsdiecker reaction using heavy metals in teh
presence of Br and CCl4
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garage chemist
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Oh, I didn't remember it correctly, it was not Vogel, it was Gattermann (the 1909 version) in which the HI/P reduction of benzophenone to
diphenylmethane was described.
EDIT: Page 301 in the Gattermann from 1909. Also reduction of benzoic acid to toluene, stearic acid to octadecane, glycerol to propane etc. are stated
as being possible with HI/P.
[Edited on 18-3-2007 by garage chemist]
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nightflight
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.. but that´s a ketone, not a carboxylic acid. Ok, Hi is expensive, but that wouldn´t be a reason to not mentioning it as it´d be an easy and
important reaction.
edit: oh-ok cool -could you provide a link? 
[Edited on 18-3-2007 by nightflight]
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garage chemist
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It is clearly stated that the HI/P reaction works with all oxygen compounds, alcohols, aldehydes, carboxylic acids etc... Look it up!
Even unsaturated compounds can be converted to saturated ones by means of HI/P, like benzene ---> cyclohexane.
EDIT: OK, link: http://www.sciencemadness.org/library/books/the_practical_me...
[Edited on 18-3-2007 by garage chemist]
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nightflight
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thanks a lot!
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solo
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| Quote: | Originally posted by garage chemist
It is clearly stated that the HI/P reaction works with all oxygen compounds, alcohols, aldehydes, carboxylic acids etc... Look it up!
Even unsaturated compounds can be converted to saturated ones by means of HI/P, like benzene ---> cyclohexane.
EDIT: OK, link: http://www.sciencemadness.org/library/books/the_practical_me...
[Edited on 18-3-2007 by garage chemist] |
I did find the reaction on page 301 as stated, but have looked for the statement, where the author makes the statement you quoted......I'm not lazy
perhaps a bit farsighted, so how about giving up the page of the 1907 publication where the information is posted.......solo
It's better to die on your feet, than live on your knees....Emiliano Zapata.
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S.C. Wack
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This all depends on what exactly you are trying to decarboxylate. I assume that the COOH is not attached to the ring, nor are groups that would cause
problems. Don't count on the Hunsdieker to give good yields on aromatic cpds.
The HI/RP is in the older editions as well, but not the newer ones. The reference given is available at Gallica, and mentions some of the other
reductions. What Gattermann says says nothing of the yield or conditions necessary in reduction of acids on a preparative scale - these are hot sealed
glass tube methods (with pressure from gas evolution as well as vapor pressure), and acids are not likely to reduce quite as easily as benzophenone.
[Edited on 18-3-2007 by S.C. Wack]
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nightflight
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What do you all think of the steps proposed in the entry post?
And how about using Al(Hg) in the Rosemund reduction -alternatively Palladiumchloride is available -the over reduction would be a good thing in this
case.
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solo
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Well since you asked, one I would react the COOH with some NaBH4 and NiCl in water at RT to get the OH then use the Hypo/I2 to reduce the OH to the
CH3........solo
It's better to die on your feet, than live on your knees....Emiliano Zapata.
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nightflight
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...that came to my mind yesterday night after reading Vogels synthesis of 2-amino-3-phenylpropan-1-ol.
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nightflight
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| Quote: | Originally posted by solo
Well since you asked, one I would react the COOH with some NaBH4 and NiCl in water at RT to get the OH then use the Hypo/I2 to reduce the OH to the
CH3........solo |
In fact it´s the PI3 that forms the alkyliodid, which then has to be reduced to yield the alkane.
So I´m now at this point, since HI redeuction needs pressure to yield 150°C and I don´t know how to perform it:
-esterification (already done with n-butanol, to provide a good leaving group and it was dry and readily available),
reduction with Al(Hg) to -hopefully- yield the alcohol,
-synthesis of the alkylhalide with 1/3P&I -> CH2I + H2PO3
-reduction with Al(Hg) getting the alkane.
Could anybody expalin how after this document: http://www.geocities.com/nepalorganic/co_acid.htm
an Alkane can be made with Grignard reagents? Is this the reaction wheere cooling to -70°C is necessary as for the gereartion of carboxyli acids by
Grignard? -sorry, did´t yet find that much on it.
[Edited on 25-3-2007 by nightflight]
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not_important
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| Quote: |
Could anybody expalin how after this document: http://www.geocities.com/nepalorganic/co_acid.htm
an Alkane can be made with Grignard reagents? Is this the reaction wheere cooling to -70°C is necessary as for the gereartion of carboxyli acids by
Grignard? -sorry, did´t yet find that much on it. |
You mean the CO2 one? Works in part because the carboxylic acid salt is formed, which isn't very reactive, and in part because it is run cold.
Alkanes are made via Grignard using halides, not acids RX + R'MgX => R-R' + MgX2
acids are OK for making alcohols or sometimes ketones.
if you're starting with a carboxylic acid you need to get it to being a halide first, the route depends on where you start and what the target is.
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nightflight
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could a halide of a acid halide be swapped for an hydrogen by a grignard reagent, what is the most convenient way to do so, anyway?
I´m thinking about sealing it in a flask with a keck clamp and some wire or string and throwing it into the micro for convenient heating (mw doesn´t
speed up ester cleavage so donßt I think it´ll speed up things here), to obtain 150°C, which doesn´t seem like too much pressure is needed to get
to this temperature.
[Edited on 25-3-2007 by nightflight]
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not_important
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| Quote: | Originally posted by nightflight
could a halide of a acid halide be swapped for an hydrogen by a grignard reagent, what is the most convenient way to do so, anyway? |
Yes, sort of. It makes a ketone, which can react with the Grignard to give a tertiary alcohol. In the bad old days it was more common to make the
Grignard, then convert it to the corresponding organo-cadmium compound and react that with the acid halide, as the cadmium compound is less reactive.
The minor problem with this is the high toxicity of cadmium and its compounds, and the tendency of the organic cadmium compounds to ignite when
exposed to air, made more interesting by the ether used as a solvent. Severe burns plus cadmium poisoning were poor incentives for recruiting
new chemists.
| Quote: | | I´m thinking about sealing it in a flask with a keck clamp and some wire or string and throwing it into the micro for convenient heating (mw doesn´t
speed up ester cleavage so donßt I think it´ll speed up things here), to obtain 150°C, which doesn´t seem like too much pressure is needed to get
to this temperature. |
Almost 5 bar if using just plain water, as a baseline. You'll have to do digging to find out for the reaction mix you plan. Be interesting to see a
wire wrapped flask in the microwave.
http://www.engineeringtoolbox.com/saturated-steam-properties...
Sealed tube runs use heavy walled tubing and put that inside steel pipe for tube failure containment. Sometimes water or some other liquid would be
placed in the pipe was well, and it would be sealed - this to reduce the pressure differential on the glass tube. Care must be taken to correctly
calculate the amount of liquid to use in order to prevent too little or too much pressure in the pipe.
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nightflight
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How convenient is a MV, when it can be heated in a secure shell in a reg. oven? ;-))
Just out of interest, could the reduction of the alcohol proced liek this:
RCH2X + 2HI + 2H3O* -> RCH3 + 2H2O + I2 ?
the I2 is then racted with the RP to regenerate the HI(aq):
3I2 + 2P + 6H2O -> 2PI3 + 6H2O -> 6HI + 2H3PO3
Theoretically it could be used less HI but with more time the rxn should go to completion, for the HI reg. is permanent, couldn´t it?
What would yo think about substituting this with the reduction in NaBH4 and F3CCO2H, price-wise ?
[Edited on 29-3-2007 by nightflight]
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roamingnome
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Barton Vs. Kolbe Decarboxylation maybye...
they join forces....
Since Barton radical decarboxylation was found threw search engine here it seems the place to ask and post
Ive been looking for interesting things to sonicate these days and radical decraboxyaltion of phenylalanine seems rather promising for interest
levels…
First:
http://www.osti.gov/energycitations/product.biblio.jsp?osti_...
The methyl radical yield rises sharply at very low concentrations of methanol…..
Methyl radicals if they are needed will form in the gas bubble and be ready to react with the bulk fluid medium at collapse. Kind of a Kolbe et al.
type of promise…..
Depending on the reaction methyl radicals can add to thermally decraboxylating phenylalanine, or if one had the specialized reagents barton
decarboxyalation produces R groups with the addition of a hydrogen ……
http://www.organic-chemistry.org/namedreactions/barton-decar...
but im pretty sure home school techniques can deliver a ester of phenylalanine that will produce the R group with out all the fancy fine sigmaaldrich
specials…
http://www.springerlink.com/content/xh07j39423831367/
Under the action of peroxides or UV radiation mercuric alkanoates undergo initiated free-radical decarboxylation with formation of alkylmercury
compounds.
Um I really don’t want to create methylmercury but it shows the trend
Other refs:
Radical Reactions in Organic Synthesis By Samir Z. Zard
Provided by google books
http://www.osti.gov/em52/1999projsum/54834.pdf
The acetylene then reacts with OH•to form methyl radicals and carbon monoxide
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Organikum
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| Quote: | Originally posted by S.C. Wack
This all depends on what exactly you are trying to decarboxylate. I assume that the COOH is not attached to the ring, nor are groups that would cause
problems. Don't count on the Hunsdieker to give good yields on aromatic cpds.
The HI/RP is in the older editions as well, but not the newer ones. The reference given is available at Gallica, and mentions some of the other
reductions. What Gattermann says says nothing of the yield or conditions necessary in reduction of acids on a preparative scale - these are hot sealed
glass tube methods (with pressure from gas evolution as well as vapor pressure), and acids are not likely to reduce quite as easily as benzophenone.
[Edited on 18-3-2007 by S.C. Wack] |
I translated once this german article from the 30s for the HIVE where they reduced all this acids and stuff with HI....
The procedure was like this:
95% H3PO4 + NaI or KI + a small amount of red phosphorus
The use of the highly concentrated H3PO4 allows temperatures which are sufficient to reduce almost everything without the need of a pressure vessel.
The authors explicitly suggested this method for use on an industrial scale.
The older industrial methods were indeed using HI with conc. HCl as solvent in a pressure vessel, or HI in concentrantions up to 72% IIRC under
pressure - nothing for the amateur.
As a laboratory method in special to reduce alcohols the GAA/iodine/red phosphorus reduction system was used, but in these times GAA and iodine were
rather expensive and chemists were poor.
The yields of the H3PO4 method were always named as >80%, H3PO4 is rather cheap and easily concentrated from the 85% of trade to the 95% asked for
by simple heating, NaI and KI are also no problem, just the red phosphorus might be for some a problem in these days of the meth madness.
There was also what SAM posted at the HIVE (times before he went insane) - a scanned page from an unnamed old book - where it was stated that HI rips
out oxygen from virtually EVERY organic molecule, if reaction conditions are harsh enough it goes next for the nitrogen.
This might explain that reducing phenylalanine with HI is not trivial as the conditions needed to reduce the acid will be near to the conditions
reducing the nitrogen. I guess in this reaction the conditions (in special temperature) have to be very well controlled and it will take some
tinkering to get them well adjusted. Then the yields should be very high as basically always with HI reductions.
/ORG
[Edited on 9-6-2007 by Organikum]
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tongqiancao
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I think this maybe easy to work
| Quote: | Originally posted by nightflight
But why is it so hard to find? all I see is reductions to alcohol, using various metal catalysts or the hunsdiecker reaction using heavy metals in teh
presence of Br and CCl4 |
Hunsdiecker reaction have been improved currently. if you have a beta-unsaturated acid as your raw material. This paper may be help:
Tetrahedron 61 (2005) 637–642.
You can get beta-arylvinyl bromides in 1-2min with high yield. Then just a reductive reagent will be needed after it.
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solo
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Reference Information
Stereoselective synthesis of (E)-b-arylvinyl bromides by microwave-induced reaction of anti-3-aryl-2,3-dibromopropanoic acids using an
AgOAc–AcOH system
Chunxiang Kuang,* Hisanori Senboku and Masao Tokuda
Tetrahedron 61 (2005) 637–642.
Abstract
(E)-b-Arylvinyl bromides were stereoselectively prepared in high yields by microwave irradiation of the corresponding anti-3aryl-2,3-dibromopropanoic
acids in AcOH in the presence of AgOAc for 0.5–3.0 min.
[Edited on 9-6-2007 by solo]
Attachment: Stereoselective synthesis of (E)-b-arylvinyl bromides by microwave-induced reaction of anti-3-aryl-2,3 dibromopropanoic (210kB)
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It's better to die on your feet, than live on your knees....Emiliano Zapata.
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Filemon
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Do you know this decarboxylation? I don't know their name.
R-COONa + NaOH + CaO + Heat => R-H + NaCO3
I have read that the aldehydes alpha-halogen they are oxidized easily to carboxilic acid. That yield has the reaction:?
Acetaldehyde + NaClO + H2O => acetic acid
or
EtOH + NaClO + HCl + H2O => acetic acid
[Edited on 10-6-2007 by Filemon]
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roamingnome
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| Quote: |
Do you know this decarboxylation? I don't know their name. |
| Quote: |
R-COONa + NaOH + CaO + Heat => R-H + NaCO3 |
well in chemistry anything can happen....
but where did the Calcium go
to a happy place?
i have been seeing that added bicarbonate facilitates decarboxylation...
So
i hold in my hand a 500 mg gelaitan capsule of L-Phenylalanine
i will separate the cellulose and Mg stearate as the only other listed ingredients.
i will add bicarbonate until a homogeneous mixture is had in water.
A catalytic amount of methanol will be added
the mixture will be sonified at 20 kHz and up to 150 Watts without temperature concerns.
i wonder the result....
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