IPN - 11-7-2007 at 02:52
Reading through some texts about terpenes I came across a simple looking pathway to limonene starting from a-pinene and would like to try it out 
. Now a-pinene can be found from turpentine but it's not the only component.
There is among other things camphene (bp. 159° to 160° C), fenchene (154° to 156° C), dipentene (175° to 176° C), some sesquiterpenes, etc.
Pinene itself boils at 155° to 156° C so simple distillation won't do any good.
I have a 500mm hempel column with a vacuum jacket and silvering but I'm not sure what kind of raschig rings should be used with it (I have 3mm, 6mm
and 8mm rings). Any suggestions?
Also are there any other ways of separating a-pinene from the rest of the terpenes?
not_important - 11-7-2007 at 08:31
Sometimes a reaction would be done on the raw material, and the workup would separate the products. This may be easier because the different
components reaact differently, or given products of greater difference in their properties. Expect to do a fair amount of research.
The packing choice is between distillation rate and number of effective plates. Expect to do multiple fractionations, taking cuts and refractionating
them, given the closeness of boiling points. You're still not going to get really clean separations with pure products.
Sauron - 12-7-2007 at 04:37
What not_important is suggesting works in some cases and in other cases would produce an inseperable mess. The point is to know in advance what the
outcome will be and proceed intelligently.
A chemical seperation might be possible, I'd have to study the structures to say more.
But I think sourcing some pure a-pinene will be FAR less trouble and expense than either method.
I bet a-pinene will be available in technical grade in like 20 L packing for about the same price as pain thinner.
Have you looked in Merck Index?
Literature references: Obtained from oil of turpentine which contains 58-65% alpha-pinene along with 30% beta-pinene, q.v.: E. Gildemeister, F.
Hoffmann, Die aumltherischen Oele Band IV (Akademie-Verlag, Berlin, 4th ed., 1956) p 39. alpha-Pinene in North American oils is dextrorotatory, in
most European oils it is levorotatory. Constituent of many volatile oils. Isoln of d- alpha - pinene from Port Oxford cedar wood oil (Chamaecyparis
lawsoniana Parl., Pinaceae): Thurber, Roll, Ind. Eng. Chem. 19, 739 (1927). Isoln of l- alpha - pinene from mandarin peel oil ( Citrus reticulata
Blando, Rutaceae): Kugler, Kovaacutets, Helv. Chim. Acta 46, 1480 (1963). Total synthesis of alpha- and beta-forms: Komppa, Ann. Acad. Sci. Fennicae
A59, 3 (1943), C.A. 41, 425 (1947); Thomas, Fallis, Tetrahedron Letters 1973, 4687; eidem, J. Am. Chem. Soc. 98, 1227 (1976). Review: Palmer, Ind.
Eng. Chem. 34, 1028 (1942); J. L. Simonsen, The Terpenes vol. II (Cambridge Univ. Press, 2nd ed., 1949) pp 105-191; D. V. Banthorpe, D. Whittaker,
Chem. Rev. 66, 643-654 (1966); Food Cosmet. Toxicol. 16, Suppl. I, 853-857 (1978).
Look at the structures of alpha and beta-pinene. If you reduce the double bond in both you arrive at a common product. If you can then reintroduce the
pi bond to form only a-pinene, you are home free. According to Merck, North American turpentine is 88-95% a mixture of the two pinenes, about 2:1 in
favor of the alpha.
You could also isolate it from Port Oxford cedar oil. or from mandarine oil. Those ought to be OTC.
[Edited on 12-7-2007 by Sauron]
leu - 13-7-2007 at 05:42
Dipentene is racemic limonene 
solo - 13-7-2007 at 07:45
Just to add to Leu's point.....wiki does a good job pointing this and other info...which should have been a basic starting point for this
thread.....solo
http://en.wikipedia.org/wiki/Limonene
Sauron - 14-7-2007 at 06:24
Here's the 1927 article from Ind.Eng.Chem. (an ACS publication) detailing the isolation of d-alpha-pinene in pure form from Oregon (Port Oxford) cedar
oil.
It looks like a primary fractionation of the crude oil and then refractionation over sodium of the a-pinene fraction, gave a high yield (83%) of that
fraction boiling over a very narrow and constant range (half a degree spread).
Even if you can't get Oregon cedar wood oil, which you probably can (try aromatherapy sources) you can very likely apply similar methodology to
American turpentine.
Have fun.
Furthermore, beta-pinene is quantitatively converted to a-pinene by isomerization with 5% or 10% Pd/C saturated with hydrogen, according to:
G.Widmark, Acta Chem.Scand. 9, 941 (1955)
W.Crocker, P.V.R.Shannon and P.A.Staniland, J.Chem.Soc. C, 41 (1966)
The total synthesis of the pinenes is rather laborious and so might not interest you but the chemistry is beautiful.
[Edited on 15-7-2007 by Sauron]
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Sauron - 15-7-2007 at 20:22
The "review" cited by Merck from I&EC in 1941 is less of a formal literature review than it is a brief (6 page) historical summary of the
development of industrial exploitation of turpentine and pine oil as chemical feedstocks during the twentieth century (at at least its first four
decades.)
While the relation of turpentine and pine oil to camphor, borneol, fenchone, etc. is interesting, what is perhaps more interesting from the standpoint
of this forum is the conversion of these compounds to benzene derivatives, including p-cymene, terephthalic acid, p-methylstyrene, cumic acid, and
p-isopropylbenzoic acid, from totally OTC and non-aromatic, non-coal tar, non petroleum sources.
[Edited on 16-7-2007 by Sauron]
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Sauron - 20-7-2007 at 02:46
Turns out there is a classical method to seperate a-pinene from mixtures with b-pinene such as turpentine. American turpentine is overwhelmingly
a-pinene while European turpentine is mostly the b-isomer, but appreciable amounts of a-pinene are still presen.
a-pinene forms a solid nitrosochloride which is insoluble and ppts out. b-pinene does not.
This is discussed in "The Chemistry of Essential Oils & Artificial Perfumes" Vol II in the forum library, the relevant section is attached.
The simplest method is given on p.42
Nitrosyl chloride is generated from satd sodium nitrate soln and conc HCL and bubbled into cold (0 C)turpentine in an equal volume of ether.
The free a-pinene can be regenerated from the nitrosochloride.
Yield depends on the origin of the turpentine and its optical rotation but as it is cheap - who cares? The preparation is facile. Do this in a hood or
use a scrubber to destroy any excess nitrosyl chloride, which is nasty.
[Edited on 20-7-2007 by Sauron]
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IPN - 26-7-2007 at 05:52
Thanks a lot for all the info.
I guess I'll distill once from sodium with the column and then dissolve the distillate in ether and treat it with NOCl.
How could have I forgotten to check Chemistry of Essential Oils & Artificial Perfumes... Oh well.
I'll take some pretty pics of the isolation & synth for your trouble. 
Sauron - 26-7-2007 at 06:11
You might also want to look into the perparation of terpin hydrate (expectorant used in cough syrups) from turpentine.
Yesm that stuff Mommy made you take tablespoons of all the time to cough up phlegm. You always thought it tasked like paint thinner, and now you know
why!