[Borek]

http://www.open2.net/science/roughscience/diy/caffeine_tea.htm

and some other ideas at

http://www.open2.net/science/roughscience/diy/diy_index.htm

I am told that caffeine experiment sometimes doesn't work. Still, looks easy and interesting.

[Yggdrasil]

That's a pretty cool procedure for extracting caffeine.  I didn't know that caffeine sublimed at atmospheric pressure.  Here's an alternative procedure in case that one doesn't work.  While the BBC procedure is more suited for anyone interested in science, my procedure would require a little more equipment and training in chemistry.

http://www.scienceforums.net/forums/showpost.php?p=202318&postcount=28

The yield for this procedure when I carried it out was about 40-50mg from three tea bags.

[joeflsts]

I just finished with the first procedure on this thread.  My yield was very low but I did in fact get caffeine!

Joe

[Borek]

I just finished with the first procedure on this thread.  My yield was very low but I did in fact get caffeine!

Have you taken any pictures?

[joeflsts]

No, but I will tonight and post here.

Joe

[joeflsts]

Here are the results of my caffeine extraction.  Now the funny part.. I'm waiting for the oil to get to 250C and it's hanging there and absolutely nothing is happening.  So I go back through my notes and start to scratch my head.. NOTHING... Then I realize that I'm sitting at 250F.  

Joe

[joeflsts]

Next picture..

[Borek]

Now the funny part.. I'm waiting for the oil to get to 250C and it's hanging there and absolutely nothing is happening.  So I go back through my notes and start to scratch my head.. NOTHING... Then I realize that I'm sitting at 250F.

Now imagine you are a space engineer trying to land spaceship on Mars

[joeflsts]

I have a hard enough time just trying to make it to work in one piece!

Joe

[pantone159]

Yggdrasil - How much is a 'pellet' of Ca(OH)₂?

I don't have such pellets available, but I do have CaO which I plan to use instead, but I'm not sure of the appropriate mass.

[Yggdrasil]

I used about ~0.5g Ca(OH)₂.

[pantone159]

I just got a few crystals.

I followed a procedure based on Yggdrasil's - http://www.scienceforums.net/forums/showpost.php?p=202318&postcount=28

I wanted the 'chemistry training' to practice.  I have read about organic chemistry techniques, and just got some decent stuff, but have never done any actual organic chemistry.  Now I was ready to try, with my home lab.

I started out with about twice the amounts in the procedure.  I boiled 4 bags of Lipton Green Tea into water, boiled that solution down,  and added about 32 g of NaCl.  Later, I added a little less than 1 g of CaO, and filtered the mess.  There was a lot of precipitate, and it took hours to filter it.  Then, I decided I wanted to get as much of the tannins out that I could, so I added more CaO, and did get more precipitate. The resulting solutions kept getting cloudy, (because of CO2 absorption?) so I had to filter multiple times.  When I finally started the extraction, the tea had become a little cloudy again.

Breaking from the posted procedure, I extracted into dichloromethane (DCM) instead of 1-propanol.  I had DCM, and I didn't have 1-propanol, and since DCM has been used industrially for decaffination, it seemed likely to be a good solvent.

After scraping, into a beaker, the gunk from the multiple filter papers I had used for the tea precipitates, I added some DCM to the beaker, stirred the mess up, and poured the DCM through the last used filter and into the sep funnel.  I shook it all up, and I got...

an emulsion.  

The layers wouldn't separate.

My books had mentioned this possibility, saying something like 'sure sucks, here's some hacks that might work'.  I tried the easiest possible remedy, going for a walk and some lunch.  That didn't work.  Then, I poured out the whole mess into a flask, and added some sodium carbonate. I hoped to precipitate calcium carbonate, filter that, and thus hopefully fix the emulsion.  I got some precipitate, and started to gravity filter this mess.  First, all the aqueous layer came down, with no problems.  Once the DCM got into the filter, which was wet, it would NOT go through.  I had to pipet off the DCM from inside the filter, let the filter dry, and then pour through the DCM part.  This was all a pain in the ass, and not recommended.

Finally, I got this all filtered, and put it back into the sep funnel, and shook it.  Layers!!  I had a cloudy, yellow-brown aqueous layer
on top of a perfectly colorless DCM layer.  And there was much rejoicing!

I made several DCM extractions, now without incident, dried them with MgSO4, and collected them in a beaker.  I put this in front of a fan by a screen door, and let the DCM evaporate.  I saw some water globules in the mix as it evaporated off, so I probably didn't dry it enough. And so I had some crystals of crude caffeine.  (I haven't weighed them yet.)  It doesn't look like that much, but there is something.

I haven't done any of the purification steps in the posted procedure (acetone, sublimation) but I hope to try.  Next time around, I would add sodium carbonate in the first place.  Dealing with a DCM-water emulsion was a pain.

[pantone159]

Continued...

The next step in Yggdrasil's procedure is to wash the crystals with acetone, which will dissolve the caffeine but not some contaminants.  So, I took my crude caffeine crystals, extracted with dichloromethane, and dissolved them in about 12 ml of dried acetone.  In my case, all of the crystals dissolved.  So, I think that when extracting with DCM, the wash-with-acetone step is unneccessary - no further separation was achieved.  This was, however, convenient in moving my crystals to a smaller beaker, which I could weigh halfway properly.  Total yield measured as 100 mg, very approximate.  (My scale only has precision of 50 mg, so this weight is +/- 70% or so  )

Next step is to try further purification, I hope to try the sublimation, and recrystallization from ethyl acetate is another purification step that I read about somewhere.

This photo is the crystals after evaporating the acetone.

[Will]

I've made the decision to buy a whole load of chemicals and lab equipment so I can do some experiments at home! I love chemistry but I haven't been able to do any experiments. Everything was soooo expensive though! It was cheaper for me to import a separating funnel from the USA than to buy here in the UK and it still worked out to be £25 , nothing compared to the total cost for everything of EXACTLY £540.00 (thanks to EMA benefits (and grandma !)) except a pair of safety glasses (or should I get goggles if I'm dealing with fuming acids etc?), which I am yet to buy- I was going to get subscription ones because I'm short sighted (I used to have perfect eyesight- I hate being blind ) but I think I'll go for the over-the-specs type.

Back to the extraction-
I will avoid the acetone step as Mark Kness advised and also because it is rather expensive and Labpack Chemicals needed some proof about what it was going to be used for, which I could just not be bothered to deal with.

I think the best way to do the sublimation is to have a 50ml beaker with the ice/salt water in it held in a 150ml beaker with a pile of the crude caffeine crystals in the middle of it which is heated. I saw a diagram of it a while back on the internet when searching on google. Are there better ways to do it?

Do you need to add calcium hydroxide if you're going to add sodium carbonate?

Also, would a buchner funnel (and the pump etc.) have solved the problem of the DCM not going through the wet filter paper?- I know this isn't part of the experiment, but it would be nice to know if it would've worked!

Does anyone think the same process could be used to extract theobromine (and trace amounts of other related dimethylated xanthines) from cocoa powder? I couldn't find any physical properties of dimethylated xanthines other than caffeine but I assume theobromine and theophylline would have very similar physical preoperties to caffeine? Does this mean you wouldn't be able to separate the dimethylated xanthines without difficulty?

Mark, would be nice to know how you got on with purifying your caffeine- looks like its a good yield!

[pantone159]

I haven't done any purification yet, other projects have taken my time.    

My sublimation plan was to use what would be a Buchner fiter setup (I have a hand pump whose effectiveness is yet untested), but putting an ice filled test tube where the filter would usually go, in the adaptor in the mouth of the filter flask.  I might not have a fat enough tube to get a good seal, we shall see.  Put the caffeine in the bottom of the flask, and hope it condenses on the ice filled tube.  The other option is recrystallization from ethyl acetate.

I think you want to add some Ca salt because Ca tannate is especially insoluble.  I don't know my tannate chemistry that well, though.  Don't know if vacuum would have sucked the DCM through, interesting question.

Can you get acetone at the hardware store?  That is what I used.  I think it tends to be quite wet, so I dried mine with some (almost) anhydrous MgSO4.

The next extraction I am going to try is eugenol from cloves.  Somebody in another thread had a lab procedure for this, and I found a reference to another somewhere on the net.  While I get around to finding the book with the full procedure, I have some ground cloves digesting in EtOH.

As far as glasses:  I hate goggles because they fog up almost instantly for me, especially if I have to work outside.  (It is usually hot here.)  So, I use safety glasses.  But when I work with strong acids etc., I have a plastic face shield that I wear on top of these for extra protection.  It was cheap, but the vendor is now defunct, sadly.