Decomposition temperature of cocaine hcl vs freebase

[Reverend Random]

Ok, I've been searching around for about half an hour but still can't find the exact answer I need.

I've been trying to understand exactly why cocaine hydrochloride is hard to smoke (or better: vaporize) efficiently. I understand that the difference between the temperature at which cocaine hcl vaporizes and at which it burns / decomposes is much smaller than with the freebase form.

I've looked up the numbers and have found the following differences. (I'm European so I'm using Celsius)

• Cocaine base melting point = 98 °C
• Cocaine HCl melting point = 187 and 192 °C

At first I thought that the higher the melting point, the better. Since the flames of lighters can easily reach 300 °C, this would make for a higher safety margin, because it would take longer before overheating the salt. However, it is the safety margin between the melting point and the pyrolisis temperature that accounts for the efficacy of smoking the freebase form, right?

So my questions are as follows.

1) Does melting point equal vaporization point? I thought you'd need the sublimation temperature instead of the melting temperature... as one wants to inhale the vapor. Doesn't heating it at the temperatures above cause the cocaine to melt instead of vaporize?
2) What is the temperature at which cocaine burns / decomposes / degrades? Is that the same as the boiling point?

I understand that this is basic knowledge for some, but I've never found this easily explained anywhere. Thanks for the help!

 

[sekio]

1. No, melt point does not equal vapourisation point for most substances. If this were so, water/ice would boil at 0 degrees C. Although, any liquid will give off *some* amount of vapour. But when you smoke cocaine, or THC, or whatever, you are trying to boil the compounds to volatilise them (not neccesarily inhale them as a gas, but nebulise/aerosolise them)

2. Degradation temperature is not the same as the boiling point. Depends on the environment. Whether or not it's wet, the presence of oxygen, presence of acids, etc. But, in general, higher temperatures will mean more degradation.

Higher temperature = more energy. More energy = more reactions will happen. And you don't want drugs reacting with air or themselves when you are trying to smoke them. So, generally speaking, lower melt points = lower boiling points = easier smoking = less charring.

This is also why people distill things under vaccuum; you can lower the boiling point that way, and distill your mixture with less charring than you would at a higher temperature.

 

[Reverend Random]

Thanks, sekio, clear explanation. However, does that mean that there's no one temperature at which cocaine fully decomposes? (and it's just that the higher the temperature, the worse any substance is off?)

And another question arises: do cocaine hcl and freebase have different set boiling points? I couldn't find them, that's why I concluded the differences had to do with the melting points. But if they're linearly related to the melting points, I got it. Is that so?

 

[sekio]

However, does that mean that there's no one temperature at which cocaine fully decomposes? (and it's just that the higher the temperature, the worse any substance is off?)

Pretty much.

do cocaine hcl and freebase have different set boiling points?

I think cocaine HCl breaks down into cocaine freebase, side products, and HCl when it "boils". But I'm not sure. It is definitely less volatile than the freebase.

 

[gewinnste]

Pretty much.



I think cocaine HCl breaks down into cocaine freebase, side products, and HCl when it "boils". But I'm not sure. It is definitely less volatile than the freebase.

A lot of the info here is wrong. Fact is that the decomposition temperature of cocaine-HCl (or any other salt of cocaine ) is lower than its boiling point, hence you cannot smoke it (of course, you can, but you'll get no effects because the cocaine is dead). Also, cocaine-HCl does NOT split up into HCl and cocaine base when heated (otherwise you wouldn't need to base it with ammonia or baking soda to yield free base coke/crack).

Btw, some substances sublime at sea level air pressure instead of boiling but that doesn't go for cocaine. Also, it would be irrelevant for smoking substances since you only care for the drug to be in gaseous form and intact, no matter if or not it went through a liquid state.

 

[serotonin2A]

There is some disagreement in the literature regarding the melting point of cocaine HCl and whether there is a melting point vs. a decomposition point. Some sources list the mp between 180-192˚C depending on how slowly the sample is heated, but other sources found that cocaine HCl decomposes at those temperatures. So with some care it may be possible to melt cocaine HCl without decomposition but it is almost certainly impossible to vaporize it.

 

[belligerent drunk]

1. No, melt point does not equal vapourisation point for most substances. If this were so, water/ice would boil at 0 degrees C. Although, any liquid will give off *some* amount of vapour. But when you smoke cocaine, or THC, or whatever, you are trying to boil the compounds to volatilise them (not neccesarily inhale them as a gas, but nebulise/aerosolise them)

Really, even solids give off vapours (however minuscule). But the general rule, the higher the vapour pressure of the substance at any given temperature, the more chance of getting it into gas phase you have applies. Salts (like cocaine HCl) tend to have quite low vapor pressures, so you may be approaching decomposition temperature when you're vapourizing the salt. But yeah, as sekio said, high-boiling drugs like THC do not really vapourize as such, but are aerosolized instead. So smoking it with some [plant] matter might help.

I think cocaine HCl breaks down into cocaine freebase, side products, and HCl when it "boils". But I'm not sure. It is definitely less volatile than the freebase.

Might sound like a stupid question, but what are the mechanics of smoking meth (as it's smoked as the salt)?