If I were to make THC in the lab, this is how I would do it (please don't be freaked out by all the chemical structures, they aren't completely necessary to understanding this story, but I find they help):
Looks pretty easy, right? haha!!!
Plants however, make THC like this (ref):
Notice that there is an extra COOH group on the THC when the plant makes it. This difference is critical to understanding why people use weed the way they do.
Please stick with me people, because this is cool. I will first explain a little bit about polarity. The basics are that water (H2O) is really polar--it has a partial negative charge on the oxygen atom, partial positive charge on the hydrogen atoms. Other molecules and parts of molecules can be polar in the same way. The OH group and COOH group in THC-COOH are the most polar parts of that molecule. Polar molecules generally boil at higher temperatures than non-polar ones, because the polar ones like to stick their negative parts to other molecules' positive parts (tee hee), and this keeps them stuck together in solid or liquid form instead of gas form.
So why does everyone talk about THC and not THC-COOH? Well, if you heat things with COOH groups, they can lose carbon dioxide and just be left with H (a hydrogen atom, not too polar). So when you heat THC-COOH in a joint by lighting the joint on fire, that heat causes the THC-COOH to lose CO2 and become THC (the same thing happens in a vaporizer). THC is less polar than THC-COOH, so once the THC molecules are formed they immediately vaporize and go into your lungs, then into your blood, then into your brain where they work their munchy-inducing magic by activating cannabinoid receptors.
|This is what happens in joints, vaporizers, & hot weed butter.|
Speaking of your brain, in order for molecules to get inside your brain and have any effect, they have to pass through something called the blood-brain barrier. It is extremely difficult for polar molecules to pass through this barrier, so turning the more polar THC-COOH (which would have trouble getting into your brain) into the less polar THC (which gets into your brain just fine) is crucial for marijuana to have the effects it is known for.
Oh, you like to make weed brownies??? Well, everyone knows you have to "activate" the weed by heating it in butter or oil first. Or is this just something that crazy potheads talk about? It turns out they're not crazy when it comes to getting high!!
|Mad Bong Scientist, via Fuck Yeah Schwag.|
Activation of the weed by heating it in butter serves to extract out all the THC-COOH molecules from the weed and into the butter. As we learned in the joint-smoking discussion above, heating the non-brain-penetrating THC-COOH molecules turns them into brain-penetrating THC molecules, and this is what happens to THC-COOH in hot weed butter. If you don't do this step, the only effect you will feel is from the relatively small amount of THC naturally present in the plant.
Finally, a brief discussion on peeing. Our bodies get rid of chemicals by slowly burning them (combining them with oxygen). This process adds groups like OH and COOH, which make the molecules more polar. Eventually they become polar enough that they mix in with water and we pee them out... pee pee... ... ... ... So, since THC-COOH in more polar than THC, our body can pee it out more easily. So when you activate, smoke (or vaporize) weed, you are actually turning THC-COOH into THC using heat, which makes the molecules less polar and more likely to go into your brain, and in addition makes it more difficult for your body to get rid of them. Weed Science!!!!