Sublimation: the only way to go

In chemistry, specifically organic chemistry, any time a reaction is done, the product must be purified. Sometimes it is easy, sometimes it is hard. Regardless, it is always a part of the reaction.

There are myriad techniques to purify compounds. In the organic labs I teach, we go through the basic ones: crystallization, distillation, column chromatography etc...

Of all of the available techniques, my favorite is sublimation. Sublimation rocks AND rolls. Sublimation describes the change of a solid to a gas. If the gas is cooled, the solid can reform. [Bonus points if you know the name of this process. It's not condensation].

Purification by sublimation involves heating a solid in a flask that has a cold finger above the solid. This can be done under vacuum or at room pressure.

Recently I had my organic students synthesize ferrocene. This reaction involves the deprotonation of cyclopentadiene with potassium hydroxide. Most hydrocarbons would never be deprotonated by potassium hyroxide, but the cyclopentadiene is easily deprotonated because the product is aromatic. Upon reaction with iron II, it forms a nice orange sandwich compound.



This product is easily purified by crystallization from hexane, but sublimation is a lot more fun. If a product can be purified by sublimation, I will do it. Without question.

Here are some pictures I snapped of the purification by sublimation of student synthesized ferrocene.

Here's the crap before purification:


Here is the setup. The cold-finger is cooled with water. The hotplate is heated to "4." Whatever that means.


After about an hour, the ferrocene deposits on the side of the flask. I usually put a Al foil tent around it to contain the heat and keep the whole flask warm. That way more of the product ends up on the cold finger.


Here's the cold finger with some purified ferrocene upon it.


This is the crap left behind.


And this is the final product.


I love sublimation!!!!!!

UPDATE: Here are some products I have purified by sublimation.

A different type of brew

Alkaloids are cool!!!!

My favorite is:



I've enjoyed it when delivered via a fine cigar, but I've never really gotten into:




I've never used or needed to use:



And I'm very glad I have never used:



And I'm very, very glad I have never ingested:



Of all of these, caffeine is my favorite, and in my opinion, the only proper caffeine delivery system is coffee. I love coffee. As far as I am concerned, the lasting legacy of the 1990's will be what I call the Starbuck's effect. The consistent and far reaching proliferation of coffee shops around the world has been a fascinating event.

Along with this ready source of a latte, the ultimate coffee drink, the availability of high quality coffee beans is 100% awesome. Even here in Minnesota, I can get some of the best coffee beans around... almost. In my opinion, the best coffee beans in the world (based on my survey which probably covers 0.0027% of all coffee beans in the world) is Peet's Coffee.

I was introduced to Peet's coffee in 1994 when I was a graduate student at The University of Nebraska. My advisor had done a post-doc in Berkeley. One of his best discoveries was Peet's Coffee. Peet's coffee + internet + UPS = excellent coffee anywhere. Try it sometime. It truly is the best.

Of all of the many ways to perform an aqueous extraction of the coffee beans, my favorite is the French press pot. Very simply, course ground coffee is steeped with hot water and a strainer pushes and holds the grounds on the bottom of the pot. Bottom line: it makes the best coffee.

Here's my press pot:

Today I'm drinking French roast from Caribou coffee, a local coffee venture. Here is 4 scoops of coffee ready to be extracted:

After adding hot (not boiling) water, the concoction is mixed and allowed to steep for 4 minutes (usually this is more like 1 or 2 minutes):

After 4 minutes, the plunger is pushed down and the grinds are sequestered to the bottom:

Then, time to pour and drink:


oooooooo, that's a good cup of joe!!!!

Favorite beers

My wife once asked me what my favorite beer was. Wow, what a loaded question. I told her, that depends. What type are we talking here? Well, I came up with a few categories and my selections in that category. Here are a few of my entries. Keep in mind, there are probably thousands of beers out there that could fit these categories, and many that are better than I have listed. Sadly, I have not tried every beer made. I am only reporting the results of my ongoing research. I will try more beers in the future.

So, my favorites:

Macrobrew: Budweiser
Cheap Macrobrew: Miller High Life Light
National Microbrew: Sam Adams Boston Lager
Regional Microbrew: Summit Extra Pale Ale (St. Paul, MN)
Local Microbrew: Schmaltz's Alt (New Ulm, MN)
Cheap Microbrew: Henry Weinhard's Pale Ale
Import Stout: Guinness
Import non-stout: Heineken
Beer better on tap than in the bottle: Leinenkugel's
Beer I can't buy here in MN: Fat Tire Belgium Ale
Beer I brought home from Germany; Warsteiner
Favorite beer I had while in Germany: All of them!]
Beer I make myself: My Experimental Ale is really, really good (by may standards).
Brewpub beer: the Stout from the now defunct Crane River Brewery in Lincoln, NE.
By Timezone (excluding beers previously mentioned):
Pacific: Sierra Nevada Pale Ale
Mountain: Moose Drool Brown Ale
Central: Sprecher Black Bavarian
Eastern: Yuengling Porter


There are so many good beers in world. I have surely left many good beers out. The research shall continue.

So, what kind of beer do you like?

Brewing chemistry: Part 2- Kilning

Once the barley has been malted, and the barley has just started to sprout, the next step is to kiln dry the grain. In some cases, the grain is roasted.

The purpose of the kilning (if that is a word) is to dry the grain, but also, in some cases, to roast it.

During the heating, some enzymes become denatured. However, most of the amylase enzymes survive. These will be utilized during mashing to liberate fermentable sugars from starch. Fortunately, during the drying phase, most lipase and lipoxygenase enzymes are destroyed. These enzymes are implicated in the formation of off flavors in beer as it ages.

A second goal of kilning, in some cases, is to roast the grain. Pale malt is typically not roasted, whereas, roasted barley is (umm, that's why they call it 'roasted' barley). During the roasting process a glorious reaction called the Maillard reaction occurs.

The Maillard reaction is a general reaction between an amino acid and a reducing sugar. Considering there are a lot of types of sugars and amino acids available, the Maillard reaction can form a variety of products. The Maillard reaction is a very important reaction in food chemistry. The products contribute to the color and flavor of browned bread, chocolate, seared meat, caramel and deep-fried death. Now, I'm not a food chemist. I'm just a chemist who likes food. My understanding is the Maillard reaction is central to what food chemist study. The following is my understanding of the Maillard reaction.

In the first step, an amino acid reacts with a reducing sugar (glucose is shown) to make an amino glucose. This part of the reaction is known as the Amadori reaction.



The Amadori complex can react with dicarbonyl compounds in a reaction known as the Strecker degradation. This results in a number of aldehydes such as, isobutyraldehyde and furfural and others. Some examples include:



Another important product of this breakdown are the melanoidins. This class of poorly characterized heterocycles contribute a dark color and a toasty aroma.

In reality, the Maillard reaction is more important during the boiling of the wort (a future post), but it does play a role in the roasting of grain.

UPDATE:
Try #2 for the images. I don't know why, but my images stopped appearing. I reloaded them above as .gif files and below as a .bmp file. Can you see it?

Bracket

I'm a casual college basketball fan. I listen to enough sports talk radio to know a thing or two about college basketball. At least enough to fill out a tourney bracket.

I'm in a pool with a few friends. There's no money involved so the IRS can call off the dogs. Of the first 32 games, I got 26 right. Not bad, but not great. The good news is, of the teams I was wrong about, I didn't have any of them advancing to the next round anyways.

I picked Ohio State to win it all. Wow, what a gamble.

What I really hate about the NCAA tourney, is having to wait 4 days for the third round. You get this massive flurry of activity during the first four days. Then...NOTHING...until the following Thursday. Another flurry, and then nothing for about a week. I hate having to wait. I know, I'd probably complain if it all happened during one week. I guess I just need to deal with it.

32 uses of beer

So, you think beer is useless. You fool!!! Read this and learn.

Anything missing?

I've done #28 numerous times. Beer-can chicken. mmmmmmmm Fantastic!!!!

Now, back to my beer bubble bath....

Gibberellic acid follow-up

Someone who read my post on gibberellic acid and its relationship to brewing was nice enough to send me a copy of the Corey papers I mentioned (JACS 1978, p.8031 and 8034). Thanks.

I was struck by one of the statements made. In explaining why gibberellic acid was so hard to make they mentioned that "a singularly diabolical placement and density of functionality serves to thwart all but the most sophisticated of approaches." I love the use of the word "diabolical." It fits perfectly.

Without going into the details of the synthesis, rest assured the paper details sophisticated approaches.

Cream Stout

In a previous post, I implied that my cream stout recipe has been perfected. That is kind of true, but I continue to tweak it. That is what is fun about homebrewing. The constant experimentation.

But, I do have a recipe that really works. The result is just plain yummy. I have 5 gallons in a secondary right now. In a week I will bottle and in another week I will drink.

Here is the recipe:

4 lb. Mountmellick light malt syrup
2 lb Munton & Fison Dark DME
0.5 lb crystal malt
0.5 lb dextrin (Cara-pils)
0.5 lb roasted barley
1 oz. N. Brewer hop pellets (bittering)
1 oz. Stryian Goldings hop pellets (aroma)
1 lb lactose
Wyeast #1084 Irish Ale yeast

The grains were steeped in 1 gallon of water at 155°F for 30 minutes. Sparged with 0.5 gallons and added to the brew kettle. The malt extracts are added to the brew kettle and the volume is adjusted to 3 gallons. The wort is brought to a boil and the N. brewer hops are added. This is boiled for 45 minutes. The Styrian Goldings hops, lactose and some irish moss are added. This is boiled for another 15 minutes. Cool, dilute to 5 gallons, pitch yeast.... wait.

Tell me what you think.

Brewing chemistry: Part 1- Gibberellic acid

Gibberellic acid is a plant hormone that induces the formation of a number of key enzymes, and in a sense, it gets things started in the brewing process. So, I thought I would start with gibberellic acid.

Beer is made from the sugars in malted barley (along with a few other key ingredients). In brief, the malting process involves soaking the barley in water to induce germination. During germination cell walls are broken down and starch is released within the grain [there is a bunch of plant anatomy that I could get into, but I'm not really interested in that]. Enzymes are formed that will eventually be used by the brewer to break down the starch into maltose. At a certain point germination is stopped and the grain is kiln dried and/or roasted. This is now malted barley, and it is ready to be mashed. I will deal with mashing in another post.

I want to zero in on what causes the starch-hydrolyzing enzymes to form. As the barley is germinating, any free carbohydrates are consumed during respiration (i.e converted to pyruvate and then CO2). Once the carbohydrates are depleted, the starving barley grain turns to its starch reserves. Since starch doesn't just fall apart into glucose, enzymes are needed. When the free glucose gets low, a signal is sent to start forming enzymes (amylase) to break up starch. The "signal" that triggers the formation of these enzymes is the plant hormone, gibberellic acid (GA3).

The structure of GA₃ is:



This is a very interesting molecule. It was first synthesized by a fellow by the name of Elias James Corey in 1978. I'd love to write a bit about his synthesis, but thanks to very limited (and embarrassingly so) library access at my institution, I can't easily get the papers. Thanks to Peter J. Stang, I can at least see the first page of the 1978 communications [JACS, 1978, v.100, p.8031 and p. 8034]

GA₃ gets the germinating plant to form mRNA that codes for the formation of things like amylase and other starch hydrolyzing enzymes. How any of the gibberellins work is not well understood. What is known is that the cells in the aleurone layer of the barley seed contain a membrane-bound receptor for GA₃. When GA₃ binds, a Myb transcription regulator is produced. This Myb protein induces transcription of the amylase gene. The amylase is sent on a tour of duty to destroy starch, but a well trained maltster will stop the malting before this takes place. The amylase is going to be used during the mashing process by the brewer.

To be continued...

Brewing chemistry: Intro

I am an extract brewer. Not by choice, but by necessity. My 5 year goal is to take the plunge and move to all-grain brewing. My limitations right now are time, space and acclimating my patient and understanding wife to the realities of my hobby.

Extract versus all-grain: The difference between the two is the source of fermentable sugars. In all-grain brewing the sugars are extracted directly from malted barley in a process known as "mashing". In extract brewing, the sugars come in the form of an extract, either dry or liquid. The sugars are extracted from the grains and dried to a powder under vacuum (or thick syrup) in a glorious factory somewhere. A typical extract recipe calls for 5-6 pounds of dry malt extract. In all-grain brewing recipes typically require 5-15 pounds of barley.

All-grain brewing requires more specialized equipment and more time. Is it superior to extract brewing? Well, that depends on who you ask. The result for either is superb beer, but with all-grain brewing there is more control over the final character of the beer. I hope to get into all-grain brewing someday.

I started writing this post and realized there were so many tangents I wanted to go on, that the post would be too long, too cumbersome and probably confusing. So, I am going to write a serial. [One of my favorite books of all time is "The Count of Monte Cristo." It was written as a serial. According to a legend I may have made up in my mind, Dumas started writing it and due to its popularity, he kept adding chapter after chapter without knowing where everything was headed.]

For every entry I am going to pick one aspect of the brewing process and write about the Chemistry involved. Hopefully, it will become a list of interesting and useful tidbits of brewing chemistry.

I must warn you: I am NOT a brewing chemist. I am a chemist who brews. Brewing is a hobby and not my career. Therefore, don't expect me to know everything.

SPME...the endgame... finally!!

OK, I realize I've been talking about this for too long. On the 3 month anniversary of the 3rd day after I started this blog (depending on timezone), I am publishing some SPME GC/MS data. This is from an old post, but I am now publishing the computer generated results. First, here is the GC trace:



Second, here are the results...... WAIT JUST A FREAKIN' MINUTE. Before you blindly read and accept the results, I must tell you, these were picked out of an Agilent library based on comparison to MS fragmentation patterns. If Rosko and Derek have taught us anything, it's that computers cannot be trusted. They are very useful, but not infallible ("I'm sorry Dave, I'm afraid I can't do that"). Regardless, let's blindly accept the data from the computer, shall we?

Here it is:


I've only picked a few of the big peaks. However, there are really no surprises. A lot of esters and higher alcohols. The SPME conditions have NOT been optimized. I have not experimented with any other fibers. I'm sure I could mess around with the conditions and find other interesting compounds.

I'd like to look for hop compounds and polyphenols (tannins). I know I'm not the first one to do this, so I'll keep looking for information related to this.

Until then, realize as you drink your beer: what a wonderful chemical concoction it is.