thirdharmonic
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anit-markovnikov HBr
say one were attempting a antimarkovnikov addition to an alkene, like styrene(monomer), and regarded BH3 as too pricey . radical HBr addition is often
mentioned in texts but as a synthetic route how is it practically done?
is it done in aqueous HBr? what concentrations, temps? what peroxides work best as initiators and what sort of concentrations?
does UV penetrate deep eneough into water to help initiate?
is my hyposthesis that BH3 is pricey correct or have i just been looking in the wrong places....i think going rates ~$300 for like .3L 10% if i
remember right
danke, kamsamnida etc.
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kclo4
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BH3 = Borane.
I don't get what you would be using that for?
Perhaps this may be helpful: http://en.wikipedia.org/wiki/Markovnikov%27s_rule
Also you should be able to find some information about this sort of stuff on the rhodium archives at erowid.
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Sauron
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Are you talking about BH3 in THF?
It's not cheap but neither is in unthinkable.
Sic gorgeamus a los subjectatus nunc.
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thirdharmonic
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yes by bh3 i meant borane /thf stabilized , avg of sources i looked at 1M 1L=$800 or there abouts. seems very expensive relative to radical HBr
addition, provided Hbr addition doesnt require "exotic" reaction conditions.
polar aqueous soltions dont seem like they would be supportive of radicals(cuz everything is all charge seperated), so really i was mainly curious if
the anti-markinikov reaction happens in Aq HBr or in a less polar solvent
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Nicodem
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There are several examples of radical addition of HBr to styrene in the literature. Why don't you do a literature search first?
PS: I'm moving this thread to Beginnings section due to lack of references.
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Sauron
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I do not know who is quoting you $800/liter.
First of all this is a 1:1 complex of Borane and THF not a solution so molarity is immaterial.
CAS 14044-65-6 Acros 175088000 800 ml <$180 US
See their website
[Edited on 2-3-2009 by Sauron]
Sic gorgeamus a los subjectatus nunc.
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gsd
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Anti Markonikov addition of HBr to alkenes is a free radical reaction in non- aqueous media. It it facilitated by presence of peroxides or UV light (
FR initiators).
eg. When gaseous HBr is bubbled in Allyl Chloride in presence of Benzoyl peroxide, it yields 1-bromo 3-chloro propane, whereas the product expected by
Markonikov rule is 2-bromo 1-chloro propane.
gsd
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thirdharmonic
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| Quote: | Originally posted by Nicodem
There are several examples of radical addition of HBr to styrene in the literature. Why don't you do a literature search first?
PS: I'm moving this thread to Beginnings section due to lack of references. |
aside from google searching , which turned up nothing, and whatever books are in my physical library, i do not have accsess to"the literature", at
least not that i know of, but if there is a free online searchable chemistry journal please point it out
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thirdharmonic
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| Quote: | Originally posted by Sauron
I do not know who is quoting you $800/liter.
First of all this is a 1:1 complex of Borane and THF not a solution so molarity is immaterial.
CAS 14044-65-6 Acros 175088000 800 ml <$180 US
See their website
[Edited on 2-3-2009 by Sauron] |
no, they did mean a 1M solution of borane in thf, (which exists as the complex) i didnt just make that up, so please dont insult my intelligence.
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