Any interest in determining nicotine--by DVAP

[kinabaloo]

How about the possibility that oxidised nicotine - it does happen slowly after a bottle has been opened, and in the cart, and presumably at heat time too - might still be at least somewhat active. Any thoughts on that?

[DVap]

Kinabaloo, oxidized nicotine, always some possibility there!

exogenesis, that graph is interesting.

Due to the pH range shown, the nicotine has to be in a system with stronger acids and stronger bases to permit the overall pH range shown. It is only natural that at lower pH, the freebase would decrease (salt formation).

I'm in a bit of a haze right now as I've not really thought much about it. It's probably important to remember that a solution of nicotine/water or nicotine/PG is not basic in the inorganic sense of an excess of free hydroxyl ions. With organic bases that own their basic behavior to basic nitrogen, you're looking at a nitrogen atom in an aromatic ring that has a lone electron pair acting outside the aromatic system in a non-delocalized fashion (so by virtue of the electron pair, not by dissociation into free hydroxyl ion). I'd expect nicotine sulfate (for example) as a salt in solution to have a pH somewhat less than 7 (as we're looking at a salt of a strong acid/weak base) So in the absense of any significant acidic species, I'm having difficulty seeing nicotine as anything but a free base.

That sound you're hearing, it's rust crackling off my brain and I could have overlooked something really simple.

[kinabaloo]

Kinabaloo, oxidized nicotine, always some possibility there!

exogenesis, that graph is interesting.

Due to the pH range shown, the nicotine has to be in a system with stronger acids and stronger bases to permit the overall pH range shown. It is only natural that at lower pH, the freebase would decrease (salt formation).

I'm in a bit of a haze right now as I've not really thought much about it. It's probably important to remember that a solution of nicotine/water or nicotine/PG is not basic in the inorganic sense of an excess of free hydroxyl ions. With organic bases that own their basic behavior to basic nitrogen, you're looking at a nitrogen atom in an aromatic ring that has a lone electron pair acting outside the aromatic system in a non-delocalized fashion (so by virtue of the electron pair, not by dissociation into free hydroxyl ion). I'd expect nicotine sulfate (for example) as a salt in solution to have a pH somewhat less than 7 (as we're looking at a salt of a strong acid/weak base) So in the absense of any significant acidic species, I'm having difficulty seeing nicotine as anything but a free base.

That sound you're hearing, it's rust crackling off my brain and I could have overlooked something really simple.

The bound or protonated nicotine molecule can be described as a salt even in solution? What happens when heated? This salt is stable enough to stay intact, not vaporise and just ash on the heater coil? Or ...?

As for the oxide - it depends whether the site of oxidation is the active group. I'm just trying to determine if a juice with substantial oxidation of the nicotine is still active / worth vaping.

[kinabaloo]

There are some idea on possible syntheses of nicotine here: New Page 1

[DVap]

As for the oxide - it depends whether the site of oxidation is the active group. I'm just trying to determine if a juice with substantial oxidation of the nicotine is still active / worth vaping.

The question comes down to... does the oxidation product still key to the nicotinic acetylcholine receptor in the brain? Since similar tobacco alkaloids such as nornicotine have some activity, I'd guess that there ought to be some activity.

Don't ask me how receptor keying in the brain works.. I really don't know! I never did take biochemistry, so it's a discipline that I struggle with.

[DVap]

I think I made an oops with mister's post a couple days back. While pyruvic acid is not optically active, and the pyruvate dehydrogenase enzyme handles it just fine, it's not the pyruvate dehydrogenase enzyme that acts upon propylene glycol but one (or more?) alcohol dehydrogenase enzymes, and these enzymes likely do have a better time with one of the PG enantiomers (I think they work better with the L than the D).

I suppose the route to optically pure L-propylene glycol would be via hydration of optically pure L-propylene oxide. Wanna guess what that would do the price? Hint, don't guess, "make it lower".

[exogenesis]

Kinabaloo, oxidized nicotine, always some possibility there!

exogenesis, that graph is interesting.

Due to the pH range shown, the nicotine has to be in a system with stronger acids and stronger bases to permit the overall pH range shown. It is only natural that at lower pH, the freebase would decrease (salt formation).

I'm in a bit of a haze right now as I've not really thought much about it. It's probably important to remember that a solution of nicotine/water or nicotine/PG is not basic in the inorganic sense of an excess of free hydroxyl ions. With organic bases that own their basic behavior to basic nitrogen, you're looking at a nitrogen atom in an aromatic ring that has a lone electron pair acting outside the aromatic system in a non-delocalized fashion (so by virtue of the electron pair, not by dissociation into free hydroxyl ion). I'd expect nicotine sulfate (for example) as a salt in solution to have a pH somewhat less than 7 (as we're looking at a salt of a strong acid/weak base) So in the absense of any significant acidic species, I'm having difficulty seeing nicotine as anything but a free base.

That sound you're hearing, it's rust crackling off my brain and I could have overlooked something really simple.

I think I recognise some of the concepts from Uni chemistry lectures

But to paraphrase, are you saying that possibly at >pH7 it's all effectively
free-base (or equivalent), due to the weakness of the organic 'base' ?

[kinabaloo]

I think I made an oops with mister's post a couple days back. While pyruvic acid is not optically active, and the pyruvate dehydrogenase enzyme handles it just fine, it's not the pyruvate dehydrogenase enzyme that acts upon propylene glycol but one (or more?) alcohol dehydrogenase enzymes, and these enzymes likely do have a better time with one of the PG enantiomers (I think they work better with the L than the D).

I suppose the route to optically pure L-propylene glycol would be via hydration of optically pure L-propylene oxide. Wanna guess what that would do the price? Hint, don't guess, "make it lower".

I did research (ok, google) this a bit but found almost nothing. Doesn't seem to be a natural source for PG as there is for VG.

Yes, the L form is usually the natural / body useful one (?) The two forms can have different effects. Used to know all this from vitamin / nutrition study years ago.

[bearscreek]

The question comes down to... does the oxidation product still key to the nicotinic acetylcholine receptor in the brain?

I've decided it really doesn't matter to me as long as I think it does.

[Mister]

Wanna guess what that would do the price? Hint, don't guess, "make it lower".

Technocrat posted (click here for that post) that the cheapest source he'd found for L PG was $40US/ml. Yikes. Not gonna be vaping that stuff!

The article I linked to in that thread (click here for the article) says at the end of a paragraph which describes how racemic PG is metabolized:
"As a result of the stereospecific preference of mammalian alcohol dehydrogenase and aldehyde dehydrogenase for L-propylene glycol, this stereoisomer is cleared most rapidly, and it has been suggested that neurologic dysfunction occurring in propylene glycol toxicity is caused by the accumulation of D-propylene glycol and D-lactate."