Sodium Thiosulfate did a great job removing the Iodine (by color change) in my experience, but when concentrating the quenched reaction solution it reeked of Sulfur - presumably because it had been contaminated with a sulfur compound of some sort. This sort of nixed the use of thiosulfate in my lab, there are other ways to quench iodine that are less offensive…but unfortunately can be more arduous.
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it will stay in the vicinity of the solvent’s boiling point unless you run a pressure reaction. If you pressurize a liquid, you can heat it beyond its atmospheric boiling point - in other words you effectively raise the boiling point of a liquid by pressurizing it such as with LPG cylinders. As an aside, temperatures above 120-ish C I’ve seen impurities come in that significantly detract from yield (reaction yields less, and subsequent isolations yield less).
Also, say a solvents BP is 100 C…if you dissolve a bunch of high boiling material (say BP 300C) into that solvent then you may find that you can raise the reaction mixture’s temperature to like…105C. The solvent will be refluxing because its at/above its boiling point, but the combined reaction mixture will indeed be a little hotter than the boiling point of the solvent alone. This depends heavily on the thermophysical properties of the solvent and solute.
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Not a chemist; thiosulfate?!?
Yeah 10-30% sodium thiosulfate is usually the first choice for quenching bromine or iodine.
But like I said, it killed the iodine dead but seemed to impart a strong residual sulfur odor which made concentration and distillation terrible experiences. We chose not to proceed down that road because (in addition to not wanting to waste time analyzing and identifying what sulfur stank we were producing) it stressed out the operators to be in a building that smelled like bulk human feces.
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It decolorized the iodine, giving NaI. Which is water soluble. ==> Iodine ends up in the water washes.
I was enquiring as to the possibility that the thiosulphate was your sulphur source.
And yeah that sounds like no fun at all…
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@Dr_Jebril and @Travelocity Please heed the warnings I’ve been repeatedly making regarding scaling the iodine reaction neat (without solvent). For your benefit and out of my own commitment to keeping people from getting hurt when I presumably could have helped them avoid it, I will say this again and provide enough detail to hopefully redirect your efforts - this reaction is extremely exothermic. The kind of exothermic that takes your neat reaction from 90C to 180C in like 3 minutes if you scale far enough beyond the vial (as little as 1 kg reaction). The kind of exotherm that exhibits a true runaway reaction where you eventually achieve temperatures that permit additional exothermic side reactions to begin cracking off and generating even more heat (think polymerization reactions). The kind of exothermic that breaks glassware and spew molten CBD/I2/HI/carcinogenic byproducts (not to mention HI/I2 vapor) everywhere. The kind of exothermic that is idiotic to try beyond a vial or small flask.
I’m not saying this because I’m out here secretly getting rich off the neat iodine reaction. I’m trying to save you time, money and your physical wellbeing. You NEED solvent to temper the reaction’s exotherm, period. The cyclization (ring closing) of CBD is rapid and releases heat, the hotter you are the more rapid the cyclization thus releasing even more heat even faster - as you generate heat you speed up the generation of more heat. By the time you see your reaction raise 5 degrees celsius, it will be too late to intervene. A solvent with an appropriate boiling point can temper this reaction, not to mention if you fail to carefully control the temperature of this reaction you create significant byproducts. Even if you attempt to run the reaction at 66 C neat, youll find its too slow to be viable and will be forced to tick up the temperature or Iodine concentration…at some point you will have either a hot enough temperature or high enough iodine concentration for the reaction to start cracking off rapidly - and you will then exotherm beyond what you can control. Do not scale neat reactions when you can avoid it, never scale neat reactions with known exotherms.
EDIT: this pertains to all CBD cyclization reactions i.e. the CBD to THC conversions are also exothermic. The ring-closing cyclization generates heat, as far as I can tell the double bond isomerization from D9 to D8 is either not exothermic or so mild that in solvent its unobservable. Acid catalyzed cyclization/isomerizations shouldn’t be attempted neat, and frankly it doesn’t behoove you because you’ll eventually need solvent just to quench the reagents. TBH I would love to design a jacketed flow reactor for this reaction because then your reactor only contains a small amount of substrate/reagent at any given time (and for only a short residence time) and its easier to disperse the heat generated. But of course flow reactors take more development work than throwing things into a batch reactor and stirring.
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Ahh, I understand. Yaknow, I don’t have a definitive answer - instead of solving the mystery we found a way to avoid it altogether. When I’ve opened up a bag/container of white sodium thiosulfate solids I don’t recall smelling anything terribly offensive, and when I mixed up my solutions in water I don’t remember the solution generating the same heinous smell I noticed in my quenched solution. Although I will state that some of the sulfur salt solutions I have made absolutely destroy nostrils and I don’t recommend dissolving any of this stuff in water and taking a strong whiff.
Again this was at least two years ago and I haven’t revisited since and its possible I overlooked something, but the emergence of the sulfur odor was notably after the quench (thiosulfate, bicarb, water, brine washes). I don’t remember the thiosulfate itself in water having that telltale doo-doo smell, but rather after its interaction in with iodine our toluene/cannabinoid solution smelled awful.
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The inter web reports that the thiosulfate is reacting with the iodine. Not sure if it would be the primary product or a secondary reaction, but “I added a sulfur compound, and now it smells like shit” seems suggestive.
I haven’t used hypo to decolorize iodine since middle school. I don’t recall the reaction product smelling like sulphur, but that wasn’t really the point of that particular mischief…
…we just needed a way of cleaning up the purple mess all over the classroom.
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Damn, I wanna watch this video but some lunatic blew up the AT&T station in Nashville so I’m piggybacking off someone else’s open internet who is barely in range -_-
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I don’t know about the iodine method.
But regarding sulfur method for CBN or clay method for THCs, various people have been running them solventless at high temps (above 150c) without running into such issues. Supplementary heat and vigorous stirring is even necessary to achieve notable advancements.
But anyway, you are totaly right no one should try new experiments directly at such scale. Moreover being able to monitor and conveniently control basic parameter such as reactor temperature and pressure should be a prerequisite.
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Yes, it is exothermic if rushed , overheated , over catalyzed , or insufficiently condensed reflux. I know from experience while using a 12 L spd for a few runs before buying a couple reactors.
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It’s either always or never exothermic.
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Variable
Boring…
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I think he means it generates too much heat if you do it fast you can’t cool it properly. Also not to be a jerk but reactions can be exothermic or endothermic based on temperature I believe, its been a long time since I did physical chemistry but remember the gibbs equation. G=/\H+/\ST
When I tried it was small scale so I didn’t see that issue.
Also when using thiosulfate I did not smell sulfur… I did it in a fumehood but cleaned it out afterwards and didn’t notice any smell.
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Not arguing, just curious: doesn’t a given reaction always end up at a lower or higher energy state? If the yields are more thermodynamically stable than the inputs, it would have to net extra energy right? Disclaimer: mechanical engineer
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There are multiple ways to look at it, /\H is what you are talking about, the products are either more or less stable than the reactants. I am a chemist so I am also interested in the equilibrium which takes into account the /\S and T part. So depending on the entropy and temperature a process can exothermic in /\H but for entropy reasons not be spontaneous.
It’s been awhile so my verbiage might be off.
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In this SOP step 2 the conversion from thc to cbn is mentioned
“Add 3L of a high boiling solvent (bp needs to be around 130*C+)”
Which solvent is suitable for this reaction?
toulene is a commonly used high BP solvent… but this SOP is not really an sop i would suggest following.
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