Thread: caffeine and hydrochloric acid.........

I read on the net that to extract caffeine from coffee beans you use a series of chemicals the first of which is hydrochloric acid (i am aware of other methods used in the actual industry)..........

my first question is what does the hydrochloric acid do?

second one is why doesn't it damage the caffeine as well, surely it must be reacting with all the substances?

As a part time learner I am also interested in the general processes to be encountered in chemistry, to refine something a chemist can go through a series of acids and bases, mix other substances at various yet specific points and then eventually reach the intended outcome. Anyone wishing to comment on how this works, how it doesn't damage (or does) the thing you are trying to extract and if what you are actually creating is something new that happens to be the intended result?

general comments on this side of chemistry welcome to an interested learner.....

I don't know what level your organic chemistry is, there's something called a partition coefficient, which is useful for conceptualizing the effectiveness of different solvents when doing extractions.

Say you're attempting to extract caffeine from an aqueous solution with dichloromethane. If you had 10 g of caffeine in there, and 8g/100ml ended up in the dichloromethane while 2g/100 ml was in the aqueous solution, then you here have a partition coefficient of 4. Sometimes you can increase the solubility of certain compounds in one solvent or another by manipulating the pH. This is because ions usually dissolve better in aqueous solutions.

I'm not aware of the uses directly of HCL in caffeine extraction.

Adding HCl turns the caffeine into a hydrochloride salt, which greatly increases its solubility in water. The proton from the HCl attaches to one of the nitrogens on the caffeine, giving it a positive charge, and the negatively charged chloride sticks to it.

It's difficult to say for sure without knowing the specific procedure you're talking about, but if it's a water extraction then I'd bet that's what the HCl is for.

thanks - so if it is a water extraction would i aim to extract the salt and then add something else to get the caffine back?

Originally Posted by fatman57

thanks - so if it is a water extraction would i aim to extract the salt and then add something else to get the caffine back?

Normally you would add a weak base (like bicarbonate) to deprotonate the nitrogen and get the "free base" back.