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S.C. Wack
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Quote: Originally posted by clearly_not_atara  | See http://en.wikipedia.org/wiki/Markovnikov's_rule#Anti-Markovnikov_reactions
The method with HBr/cat. H2O2 is a classic; you can find examples in most chemistry textbooks (you can usually find a cheap one at charity
book-selling events and the like). Wiki does describe a synthesis of phenylacetaldehyde using a similar methodology with water and phenylacetylene.
See also:
http://www.chemicalforums.com/index.php?topic=58919.0 |
In other words, no. OK.
PS: Has any chemistry book ever mentioned a HBr/H2O2 in any preparative context? BTW that's bromine and water, etc.
Really I want to know if these things are out there, but I'm also kind of hinting that if they're not...the directions that are out there to put the
Br at that spot are specific and it looks like they have to be. But that's not all that important because no one will go to the aldehyde from there
anyways.
[Edited on 12-2-2016 by S.C. Wack]
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clearly_not_atara
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| Quote: | | In other words, no. OK. |
http://www.chem.ucalgary.ca/courses/350/Carey5th/Ch06/ch6-4-...
| Quote: | | PS: Has any chemistry book ever mentioned a HBr/H2O2 in any preparative context? BTW that's bromine and water, etc. |
http://pubs.acs.org/doi/abs/10.1021/ja00176a075
http://pubs.acs.org/doi/abs/10.1021/jo00110a040
I guess it turns out other catalysts are better. Either hv or RCOCBrR'R"/O2 (hv sounds much easier).
[Edited on 12-2-2016 by clearly_not_atara]
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S.C. Wack
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Peroxide and hydrogen peroxide continue to be different things, in your links there is no hydrogen peroxide. Also, organic peroxide gives mainly the
wrong isomer under these nonspecific conditions (solvent should be mentioned).
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clearly_not_atara
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One is a subset of the other. Regardless, your complaint is offtopic. The anti-Markovnikov addition of HBr to styrene is simple to achieve; H2O2 might
not be the best catalyst, but who is going to publish a synthesis of something so trivial, especially if the method is suboptimal? The other papers
provide much better ideas.
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zed
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http://www.google.com/patents/US7582750
Oh, the above paper? About a page or two in, they cut to the chase.
The tables of results, and conditions, are present, but they have been compressed.
When styrene (20) was treated with 1.03 equiv Cl2pyNO and 1.0 mol % 1 in refluxing CH2Cl2 for 5 h, a mixture of styrene oxide and phenylacetaldehyde
(27) was obtained in 90% and 10% yield, respectively (Collman et al. J. Am. Chem. Soc. (1986), Vol. 108, page 2588; Burrows et al. J. Am. Chem. Soc.
(1988), Vol. 110, page 6124; Minisci et al. J. Am. Chem. Soc. (1995), Vol. 117, page 226; Gross et al. Angew. Chem. Int. Ed. (2000), Vol. 39, page
4045; Gray et al. Angew. Chem. Int. Ed. (2001), Vol. 40, page 2132). To our surprise, adding more catalyst 1 and allowing the reaction to proceed for
a longer time resulted in complete conversion of styrene oxide to aldehyde 27. For example, reaction of styrene with 1.03 equiv Cl2pyNO in the
presence of 2.0 mol % 1 in CHCl3 at 60° C. for 12 h afforded 27 in 99% yield; no benzaldehyde was observed (Gray et al. Inorg. Chim. Acta (1998),
Vol. 270, page 433). Other styrene derivatives 21-25 could also be converted to the corresponding arylacetaldehydes 28-32 in excellent yields (FIG.
6). However, for the non-aromatic alkene 26, only the epoxide product was obtained.
[Edited on 12-2-2016 by zed]
[Edited on 12-2-2016 by zed]
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S.C. Wack
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| Quote: Originally posted by clearly_not_atara | | One is a subset of the other. Regardless, your complaint is offtopic. The anti-Markovnikov addition of HBr to styrene is simple to achieve; H2O2 might
not be the best catalyst, but who is going to publish a synthesis of something so trivial, especially if the method is suboptimal? The other papers
provide much better ideas. |
You're telling me how easy it is, but I bet you haven't even read the original literature that started these textbook sentences. H2O2/HBr preparations
are in fact out there and numerous, as expected the reactions are those of bromine and are obviously not radical additions. Feel free to cite a
preparation with radical hydrobromination on any double bond that uses just H2O2 and HBr.
There is no such thing as a catalytic amount of hydrogen peroxide in HBr, or vice versa. There is no propagation, there is a reaction until one is
gone and that's it. Bromine, water, and styrene is a recipe for styrene bromohydrin.
(EDIT: vice-versa was a step too far!!! Obviously HBr with H2O2 oxidant and the molecule being operated on gives bromine then HBr then back to
bromine.)
It's true, responding to your post, I have nothing on topic to say. The reactions of styrene chlorohydrin in the vapor phase however is on topic
regardless of a certain lack of convenience:
Attachment: jacs 67_518_1945.pdf (384kB)
This file has been downloaded 938 times
[Edited on 13-2-2016 by S.C. Wack]
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clearly_not_atara
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1. You're wrong, I have read it.
2. No. I'm obviously referencing a reaction that's common knowledge, if I were specifying conditions I'd give them. I've no reason to encourage your
flamebaity nitpicking.
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S.C. Wack
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| Quote: Originally posted by clearly_not_atara | 1. You're wrong, I have read it.
2. No. I'm obviously referencing a reaction that's common knowledge, if I were specifying conditions I'd give them. I've no reason to encourage your
flamebaity nitpicking. |
There is absolutely no common knowledge about using hydrogen peroxide in place of organic peroxide in this reaction, because it isn't possible.
Hydrogen peroxide is not going to be regenerated from water full stop. If saying that your impossible reaction is impossible is nitpicking, maybe
you're at the wrong site. If you wish for me to stop telling you that you're wrong, all you have to do is either prove you're right or stop making
these claims.
[Edited on 14-2-2016 by S.C. Wack]
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Nicodem
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Before this end up with unnecessary misunderstanding and accusations...
Neither hydrogen peroxide or any other peroxide can be used as a catalyst for the radical addition of HBr on alkenes. In fact, I know no catalysts for
this reaction (though they might exist). Radical additions of HX (where X is Br, I, SR, PR2, etc.) require some kind of radical initiation
which can be chemical (with radical initiators like AIBN, diacyl peroxides, oxygen, etc.), photochemical (UV) or radiochemical (gamma or other
ionization type). The reaction is rapid (it's a radical chain reaction) and for this reason it does not even need catalysis.
Hydrogen peroxide is rapidly reduced by HBr to yield H2O and Br2 and cannot be used neither as a catalyst or radical initiator.
In fact, for this reason hydrogen peroxide is commonly used as an in situ oxidant for HBr in electrophilic aromatic brominations.
Radical addition of HBr on styrene is not some trivial reaction. A lot of conditions need to be fulfilled to slow down the otherwise much faster
competing reactions like the electrophilic addition and polymerization. Anhydrous conditions and a highly non-polar solvent are used to prevent the
electrophilic addition of HBr (already gassing the reaction mixture with dried HBr is not trivial). Traces of water will catalyze the electrophilic
addition yielding 1-bromo-1-phenylethane. Low styrene concentrations (e.g., by slow addition of styrene) and higher HBr concentrations can slow down
the polymerization.
Preparative examples of phenetyl bromide preparations from styrene using the radical HBr addition do exist, but as far as I could find, they are all
but one written in Chinese (though admittedly, I did not spend much time searching). Yields can be excellent, except that achieving them is not
simple. Here are a few Chinese references from a 5 minutes SF search:
Huaxue Shiji, 2006, 28, 326-328 (in CCl4, UV initiation, 96% yield)
Huaxue Gongye Yu Gongcheng (Tianjin, China), 23(5), 385-388 (in heptane, AIBN initiation, 92% yield)
Shandong Huagong, 2004, 33, 8-34 (in petroleum ether, unspecified initiator, 91%)
CN101255095 (in heptane, (BzO)2 initiation)
CN1429799 (in 1-bromohexane, AIBN initiation)
JP09040591 (O2 initiation)
…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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clearly_not_atara
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I posted a ref in English four posts up:
http://pubs.acs.org/doi/abs/10.1021/jo00110a040
It discusses the reaction in some detail. In any case, is it *really* too much for me to expect people to be familiar with the radical addition of HBr
to alkenes (other HX suck for this reaction so they don't matter) and either know how to do it or know where to look it up? Yes, I got the conditions
wrong. Congratulations. But I subsequently got the conditions right and yet here we are arguing about a line in a post from a week ago that doesn't
even have any words in it.
[Edited on 15-2-2016 by clearly_not_atara]
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S.C. Wack
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We're using the term catalyst loosely, obviously. The particular examples I've had in mind are JACS 61, 2693 (1939) and the patent it mentions,
GB438820.
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madcedar
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| Quote: Originally posted by phendrol | Well to be honest I couldn't do much because I haven't got a vacuum pump. An aspirator is no good because water pressure is to low at my place.
Because of that I can't purify the epoxide via vacuum distillation. When I made a run with it, the silica gel was covering with tar pretty fast.
But this method sounds super easy. I definitely will try it and post results. Thanks!!!
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You may not have used enough solvent and I think everything has to be anhydrous to get from stryene oxide to phenylacetaldehyde via silica gel,
otherwise you'll end up with the diol.
Any comments on this will be very welcome.
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Chemi Pharma
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Everybody here in this discussion post are talking about styrene as starting material to sintesize some phenylacetaldehyde. Anybody thought about the
use of phenethyl alcohol as starting material?
Phenethyl alcohool is sold at cheap prices by perfumery flagrancies stores as a litre bottle.
Just oxidate the alcohol with CA(OCL)2 - HTH pool and alumina in a microwave for 2 minutes or reflux the mixture for 4 hours and you get pure
phenylacetaldehyde in >95% yeld.
See the papers below about alcohol oxidation to aldehydes by HTH pool and alumina:
Attachment: alcohol oxidation by CaOCL to aldehydes.pdf (161kB)
This file has been downloaded 900 times
Attachment: Microwave Assisted Selective Oxidation of Benzylic Alcohols with Calcium Hypochlorite under Solvent-Free Conditions.pdf (62kB)
This file has been downloaded 839 times
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byko3y
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None of those articles mentiones 2-phenylethylalcohol. And that's for reason, because the procedure does not work for this substrate, yielding a
complex mixture of products.
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Chemi Pharma
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Do you have references about that? about only working with benzilic alcohools and not with phenyl alkyl alcohols with alifatic chains?
I trace a parallel with the oxidation of alcohols to acids with nickel peroxide (hipoclorite + nickel salt) that i read from an japanese article, that
i bring to you all, below, as an attachment.
If you oxidate the phenyl alkyl alcohol at cold temperatures like 0º C, this afford phenyl alkyl acid with no chain split. See somewhere in the paper
that they got this result with phenyl propyl alcohol with 70,5% yield of phenyl propionioc acid and a small amount of benzoic acid:
"...In the cases of alcohols possessing an active
methylene group in the molecule, the methylene
group was in part simultaneously oxidized at room
temperature to give compounds with less carbon
atoms. When the reaction temperature was low-
ered in such cases, however, the oxidation of a
carbinol group proceeded so predominantly that
the corresponding acid was obtained in good yield.
Thus the oxidation of y-phenylpropyl alcohol at
0" afforded 70.5% yield of y-phenylpropionic acid
together with a small amount of benzoic acid,
whereas at 30" it gave 56.7% yield of y-phenyl-
propionic acid and 17.6% yield of benzoic acid..."
Hey! Isn't a good way to produce tons of ever watched Phenyl Acetic Acid?
Attachment: Oxidations with nickel peroxide (NICL2 + NAOCL).pdf (567kB)
This file has been downloaded 935 times
[Edited on 9-5-2016 by Chemi Pharma]
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clearly_not_atara
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Just use an Oppenauer oxidation with benzoquinone, much simpler. You can use aluminum t-butoxide or just react your 2-phenylethanol with Al amalgam to
get things started, IIRC.
https://www.researchgate.net/publication/244761206_On_Quinon...
This is usually the easiest alcohol oxidation.
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Chemi Pharma
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Thanks Clearly for the reference.
Ok I understood about the oppenauer, but didn't understand what you means about "just react your 2-phenylethanol with Al amalgam to get things
started".
The latter thing you said it's about a reduction reaction, given probably phenylethane.
Could you make the things clear(ly) to me?
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byko3y
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Chemi Pharma, I have no references at hand, that's just my speculations, which happen to be true.
2-phenethyl alcohol is extreemely labile to oxidation at benzylic position, even more than 3-phenylpropanol. Of course, nickel peroxide might give as
high as 50% yield for phenylethanol oxidation to phenylacetic acid.
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Chemi Pharma
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Ok byko3y, what do you think about a moffatt oxydation of 2-phenylethyl alcohol with DMSO and P2O5 and Et3N? By
analogy to the Swern procedure, it seems the different mechanism of this type of alcohol oxidation doesn't affect the benzilic carbon.
Do you think i can achieve phenylacetaldehyde this way?
Attachment: DMSO - Phosphorus pentoxide - triethylamine (PDT) oxydation to aldehydes and ketones.pdf (278kB)
This file has been downloaded 757 times
[Edited on 10-5-2016 by Chemi Pharma]
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clearly_not_atara
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The reaction of an alcohol with aluminum amalgam or activated aluminum produces an aluminum alkoxide and hydrogen:
6ROH + 2Al >> 3H2 + 2Al(OR)3
The alkoxide is oxidized to the aldehyde by benzoquinone.
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Chemi Pharma
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Thanks for the explanation Clearly. I've got it.
Do you have any papers about aluminium alkoxides oxidation with benzoquinone?
And what do you think about a moffat oxidation of 2-phenethyl alcohol?
Could afford phenylacetaldehyde in reasonable yields?
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CuReUS
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atara,that's a smart idea,using the alcohol you want to oxidise to make its own alkoxide.Then you wouldn't have to use Al-tert butoxide separately.
But isn't there a chance of condensation of the aldehyde formed due to the primary alkoxide(from phenyl ethanol ? ).Isn't that why they use a
sterically hindered and bulky alkoxide like t-butoxide ?
if oppenauer oxidation is done,instead of using benzoquinone,cinnamaldehyde could be used,which would get reduced to cinnamyl alcohol.
other amateur friendly ways to oxidise alcohols to aldehydes would be NBS,lead tetracetate/pyridine, SeO2,DMP,Oxone to name a few.
[Edited on 12-5-2016 by CuReUS]
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clearly_not_atara
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Big problem with DMSO oxidations is the Me2S byproduct. This flammable toxic gas is not easy to scrub from efflux gas because it's very nonpolar. The
safer modification is the Corey-Kim version, using a haloimide and catalytic amounts of a thioether.
It's not clear what the best thioether is -- methionine hydantoin comes to mind, but has solubility issues. Dodecyl methyl sulfide is popular. There
are few OTC options; dibenzyl sulfide isn't too hard I guess.
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CuReUS
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not to mention the stench
| Quote: Originally posted by CuReUS |
if oppenauer oxidation is done,instead of using benzoquinone,cinnamaldehyde could be used,which would get reduced to cinnamyl alcohol.
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cinnamyl alcohol could be converted to propenylbenzene with this reaction
https://en.wikipedia.org/wiki/Barton%E2%80%93McCombie_deoxyg...
or this-http://www.organic-chemistry.org/abstracts/lit3/641.shtm
also I was thinking,How about using alcohol dehydrogenase enzyme to oxidise phenylethanol to phenylacetaldehyde ?
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karlos³
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Pyridinium chlorochromate is also a very amateur friendly oxidant, especially for the conversion of alcohols to aldehydes. I like it very much, as it
is easy to prepare and a convenient reagent.
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