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Old 11-14-2007, 03:04 AM   #1
Parker36
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Default Alpha Acid Chemical Makeup

Anybody know the chemical makeup/IUPAC name/diagram of alpha acid? Just curious

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Old 11-14-2007, 03:19 AM   #2
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Yeah, actually, I put it in the wiki.

http://www.homebrewtalk.com/wiki/ind...id#Alpha_acids

Working on R-groups for all the alpha acids, but no time.

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Old 11-14-2007, 03:32 AM   #3
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Very cool. How many R-Groups are there? Does the isomerization occur within the R group itself or at the other chiral center?

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Old 11-14-2007, 03:46 AM   #4
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Quote:
Originally Posted by Parker36
Very cool. How many R-Groups are there? Does the isomerization occur within the R group itself or at the other chiral center?
You're a geek.


Fortunately, so am I. If you want to really read the fundamentals of brewing chemistry and microbiology, I suggest looking at the CRC Guide to Brewing Science and Practice. CU Boulder probably has a copy in the library.

Give me a few minutes in ChemDraw and I'll have your answers...

EDIT: There's 51 pages on the chemistry of hop constituents alone...
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Old 11-14-2007, 04:00 AM   #5
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If they made me take all that goddamn chemistry I'm going to put it to use somehow

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Old 11-14-2007, 04:32 AM   #6
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There's 6 identified R-groups, (note that I modified the R in the picture such that the ketone is now part of "R").

R, alpha-acid
isovaleryl, Humulone
isobutyryl, Cohumulone
2-methylbutyryl, Adhumulone
propionyl, Posthumulone
4-methylpentanoyl, Prehumulone
hexanoyl, Adprehumulone
4-methylhexanoyl, unnamed


The following papers are probably of interest to you:

MOIR, M. (2000) J. Amer. Soc. Brew. Chem., 58, 131. (of particular interest)
STEVENS, R. (1967) Chem. Rev., 67, 19.
WINDISCH, W., KOLBACH, P. and SCHLEICHER R. (1927) Wochschr. Brau., 44, 453.

The Moir paper in the JASBC is a very good one, as it provides a millenium-review of what we know of hop chemistry. It was quite a good read, in fact. In it, it references the following paper which proposed the specific mechanisms of the isomerization:

De Keukeleire, D., and Verzele, M. The absolute configuration of
the isohumulones and the humulinic acids. Tetrahedron 27:4939-
4945, 1971.

Unfortuanately, I don't have access to Tetrahedron like I do the JASBC, but I'll let you know what I find when the article comes in.

So, the mechanism I am unsure of, but it doesn't occur on a stereo center of the R-group:

http://www.homebrewtalk.com/wiki/ima...lpha-acids.png

Wish I had more to say about it, but between not having the paper handy and risking copyright infringement of what I've got, this is what I can tell you.



Remember, it's all just chemistry.

EDIT: Wow that image it huge...

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Old 11-14-2007, 05:36 PM   #7
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Here's a plausible mechanism for isomerization of humulone proposed by De Keukeleire. As it turns out, the ketone in the R-group is essential for isomerization. All the R-groups listed above contain a ketone.


http://www.homebrewtalk.com/wiki/ima...merization.png

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Old 03-11-2009, 02:28 AM   #8
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Quote:
Originally Posted by mrkristofo View Post
CRC Guide to Brewing Science and Practic
A google books preview is availible here: Brewing: science and practice - Google Book Search

Fortunately, it's mostly there.

And if you're indifferent on the copyright stuff, the whole thing is hosted http://rapidshare.com/files/107178743/Brewing_Science_and_Practice__2004_.pdf
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