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How much/what strength KOH is this?
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interrupt

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How much/what strength KOH is this?

 Wed Mar 09, 2005 1:00 pm		 Reply with quote
The following is the beginning of a description of a safrole to isosafrole process:

Quote:
Potassium hydroxide (10-12g, 1-2 mole%) was added to 800g safrole (from sassafras oil fractionally distilled twice) situated in a 2000ml round-bottomed flask


Please can someone cleverer than I Wink explain what "10-12g, 1-2 mole%" means. I know what a mole is but don't see what this ammount/concentration of KOH would be. I know what 10-12g means too! Just don't get the 1-2mole% part.

The process is described in the following document (Rhodium mirror):

http://12.162.180.114/dcd/chemistry/isomerizafrole.html

Cheers
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Nicodem

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 Wed Mar 09, 2005 4:19 pm		 Reply with quote
It only gives the molar % of the catalyst in relation to safrole:

n(safrol) = m(safrol) / M(safrol) = 800g / 162g/mol = 4.93mol
n(KOH) = m(KOH) / M(KOH) = 10g / 56.1g/mol = 0.178mol

so:

mol%(KOH) = n(KOH) / n(safrol) = 0.178mol / 4.93mol = 3.6%

Therefore, it is not even correctly given in the text itself. The point is actually, that it states that you only need a few % of the catalyst. In preparation itself this information is however obsolete.
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interrupt

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 Thu Mar 10, 2005 3:50 pm		 Reply with quote
Thanks Nicodem. I kind of see what you mean.

Quote:
In preparation itself this information is however obsolete.


What do you mean here though? Is this method to get isosafrole from safrole obsolete? Or do you mean the way the ammount of KOH is described is obsolete?

If this is a valid method to obtain isosafrole, then is it OK just to add a few % KOH as a catalyst.

Sorry for the torrent of questions! I Like to discover stuff for myself but have found safrole to isosafrole conversion pathways quite sparsely documented compared to other areas.

Any links to good information about this particular step is very much appreciated
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IndoleAmine
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really!?

 Thu Mar 10, 2005 10:07 pm		 Reply with quote
No, it is a valid method (as I already told you). I think he just meant the information being obsolete, as 1-2% of KOH (by weight of safrole used) is enough and reflux necessary, with potassium butoxide or calcium hydroxide formed in situ if you like, or under vacuum to lower the reflux temp. - or with simply plain reflux at stp...


See also:

Simple reflux:
http://12.162.180.114:90/synthetika/hiveboard/methods/000435321.html

Reflux with nBuOH:
http://12.162.180.114:90/synthetika/hiveboard/methods/000526965.html

Reflux under vacuum:
http://12.162.180.114:90/synthetika/hiveboard/newbee/000534870.html

Reflux with CaO/KOH:
http://12.162.180.114:90/synthetika/hiveboard/methods/000496743.html

Rhodium's isomerization review:
http://12.162.180.114:90/synthetika/hiveboard/methods/000172945.html
(and you might also want to take a look at http://12.162.180.114/dcd/chemistry/isomerizafrole.html ...)


And next time, look it up for yourself, m'kay!? "sparsely documented", pfffff................ Rolling Eyes


i_a

Last edited by IndoleAmine on Fri Mar 11, 2005 12:46 am; edited 1 time in total
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IndoleAmine
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!?

 Thu Mar 10, 2005 10:08 pm		 Reply with quote
Not to mention the references on bottom of the isomerization review document found on Rhodium's... ("sparsely documented"!!) Confused
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interrupt

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 Fri Mar 11, 2005 12:43 pm		 Reply with quote
DOH! Embarassed OK, *not* sparsely documented!

And thanks for the links - I'm going to get reading...
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