Author Topic: why use a solvent at all?  (Read 4280 times)

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indole_amine

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why use a solvent at all?
« on: October 08, 2004, 11:19:00 PM »
Why should a solvent work better in terms of promoting the H2O to the dessicant? Simply placing the LA in a desiccator under vacuum and slight heating...

(can be improvised with RBF, ground-glass hose adaptor and heating mantle - filled with mol. sieves and containing a test tube/vial or similar with your ergot carboxyl compounds(?))

But be careful, this may be considered rocket science!  :P

No, just joking. But I really think that dissolving the hydrate in DCM/similar wouldn't be of any advantage; and further the dehydration requires elevated temperatures and reduced pressure to proceed, and I doubt that DCM or CHCl3 have such a great affinity for water that it will positively affect the drying process. Have you any reason to believe that solvent power in this case suffices instead of heating under high vacuum? Unless you have, I would say that the combo vacuum/heat and the H2O removal through vapor phase these two factors facilitate.

And molecular sieves are also a very suitable gas drying agent...
 

indole_amine

Lilienthal

  • Guest
In theory this should work fine :-) .
« Reply #1 on: October 09, 2004, 02:45:00 AM »
In theory this should work fine  :) . Keep in mind that in reality the lysergic acid might be absorbed by the molsieves or that the the molsieve might catalyze degradation reactions (pure amines over molsieves turn brown over a week or so). So better try it with a small amount of pure substance first.

indole_amine

  • Guest
decomposition maybe - but not without contact...
« Reply #2 on: October 09, 2004, 03:18:00 AM »
Did you mean solid imines in a desiccator loaded w/sieves 3A? And they partially decomposed after already one week? I know several rxns where imines are very stable towards being dried with sieves, even when dissolved in various solvents during drying  ;)  - I think that especially in a vacuum, the sieves shouldn't give off any ions(?) that could hurt the lysergic acid being deposited in a separate open container, sitting on a nice bed of zeolithes...

References for molecular sieves of any type giving off trace particles under reduced pressure? Eager to hear...


indole_amine

Lilienthal

  • Guest
It was a typo, I was talking about liquid...
« Reply #3 on: October 09, 2004, 10:39:00 AM »
It was a typo, I was talking about liquid amines.

Bubbleplate

  • Guest
Oven Drying vs. Solvent Drying
« Reply #4 on: October 09, 2004, 02:14:00 PM »
Well, the reason I'm leaning toward drying in solvent vs. vacuum oven, is that I'm just very leary about putting a sensitive material like Lysergic acid in an oven and heating, even with a hard vacuum. I'm thinking that with a solvent like DCM, water is somewhat miscible and the Molecular sieves (4A) should just suck it up. However, I'm not sure of the strength of the hydrate bond in Lysergic acid...

Lilienthal

  • Guest
There is nothing like a 'hydrate bond', in a...
« Reply #5 on: October 10, 2004, 09:14:00 AM »
There is nothing like a 'hydrate bond', in a hydrate the water is in the crystal structure. You have to use a solvent in which your compound is soluble, otherwise there wouldn't be a way for the water to escape the crystal. There is a competition between the compound and the molsieve for the water. Obviously the association with the molsieve is many orders of magnitude stronger (otherwise it wouldn't be a drying agent).

wyndowlicker

  • Guest
Whats what?
« Reply #6 on: October 28, 2004, 12:09:00 PM »
Hey now,


Ok so then your saying the best process for releasing the hydrate bond is to disolve in anhydrous solvent then use mole seives to dry.Does anyone have any hard data on this subect or are we guessing. ;) It sounds like theres some worrys about the seives sucking it up.Whats the likely hood of this reducing yields more than if the LSA is dried but under full vacuum at 40C for several hours.both cause yield loss.Whos got the experienced answers related to this particular synthesis. :P


indole_amine

  • Guest
sieves + dessicator + heat + vacuum = good drying
« Reply #7 on: October 28, 2004, 02:40:00 PM »
What about using just an evacuated dessicator filled with molecular sieves; and heat that just to 45°C for several hours (rather than 90°C)?
:)


indole_amine

wyndowlicker

  • Guest
could bee.
« Reply #8 on: October 28, 2004, 09:08:00 PM »
Hey now,


So the question is does mole seives pose a possible loss of LSA and how much.I guess someone has tried to at least disolve 1/20 to a gram of LSA and dry with mole seives in solvent.We'll see if there is any loss after drying and weighing odviously,anyone have a reference? :P


Lilienthal

  • Guest
You cannot remove crystal water just by ...
« Reply #9 on: October 29, 2004, 12:13:00 AM »
You cannot remove crystal water just by letting it stand over drying agent  ::)

indole_amine

  • Guest
why not?
« Reply #10 on: October 29, 2004, 03:36:00 AM »
Sure you can! (at least with SnCl2, stored over CaCl2 at room temp for several days...)

And why use a solvent at all? Molecular sieves work fine for drying gases; and all drying processes rely on the fact that crystal water is always given off as soon as the drying agent's hydrate bond represents a less energy-consuming type of bonding compared to the substrate, meaning that the drying agent has a greater affinity for water than the substance to be dried, either alone or with the help of vacuum and/or heat (which both make it harder for the water to stay in the crystal lattice, therefore it leaves at some point..). Bonus: ions have a hard time wandering through air, not to speak of vacuum. I doubt that any reaction between the drying agent and compound to be dried can take place in a dessicator.

Mol sieves further work a lot better if heated, so I don't see why you would want to expose any ergot compound to the possible danger of destruction, just to be able to dry it together with some solvent... ::)

Maybe I should've asked "why in any way should a solvent be better in terms of transporting the water to the sieves, compared to plain air having a pressure of <1 atm?"

it all depends on the thermal gravimetry peak:

Post 506649

(Rhodium: "drying ammonium acetate", Newbee Forum)

Post 71294 (missing)

(lugh: "Re: Anhydrous or not....", Methods Discourse)

Post 442008

(L_jamf: "ammonium acetate preparation", Chemistry Discourse)



indole_amine


Bubbleplate

  • Guest
Molecular Sieves Are NOT Like Ordinary
« Reply #11 on: October 29, 2004, 05:54:00 PM »
Drying agents like Magnesium Sulfate or Calcium Chloride.
Molecular Sieves are crystalline metal aluminosilicates having a three-dimensional interconnecting network of silica and alumina tetrahedra. Natural water of hydration is removed from this network by heating to produce uniform cavities which selectively adsorb molecules of a specific size. So, for example, Type 4A Sieves will selectively absorb H2O molecules and leave behind larger molecules such as Lysergic Acid. Very little, if any, loss of LSA should occur.
I guess my original question should have been, which solvent would be the best "substrate" to dissolve LSA in order to have the Molecular Sieves suck up the H2O and leave behind dry LSA...

indole_amine

  • Guest
Et2O, DCM, EtOAc etc.
« Reply #12 on: October 29, 2004, 09:43:00 PM »
I know about mol. sieves, and I know that they're fairly inert in most cases. (this excludes strong acids and bases for example, as well as ethanol). But why not use air as transportation medium? Sieves were originally designed for quick gas drying during oil refining processes AFAIK. And halfway evacuated air is pretty damn inert to almost everything, believe me.

Anyway: DCM can take up quite a lot of water, so this might be the solvent of choice, or ethyl acetate maybe - and diethyl ether should work fine, too. Maybe you can even use plain methanol, but I'm not sure about moderately polar solvents - only about the inertness of the mentioned nonpolar solvents.
Not suited would be for example cyclohexane or benzene, as their maximum water content is fair too small.

But you should consider that you can do more damage to your precious molecule if you dissolve it in a solvent. And: the advantage of using air as the drying medium is that you can apply vacuum. Which helps a lot in drying! Try that with ether... :P


indole_amine

Lilienthal

  • Guest
indole_amine: the water sticks in the crystal...
« Reply #13 on: October 30, 2004, 04:06:00 AM »
indole_amine: the water sticks in the crystal structure and will NOT crawl out there, at least not in reasonable time and without heating it up!

Bubbleplate: I didn't say that lysergic acid could be absorbed like water to the sieves, I was talking about unspecific binding, similar to the adsorption to silica gel. I'd guess that the more polar the solvent the less likely is such adsorption.

I suggest that everybody rereads the whole thread again before posting redundant or wrong stuff...  :)

indole_amine

  • Guest
?
« Reply #14 on: October 30, 2004, 07:52:00 AM »
indole_amine: the water sticks in the crystal structure and will NOT crawl out there, at least not in reasonable time and without heating it up!

Exactly - you have to create conditions which allow for the water to be given off; these include applying heat, diminished pressure and a drying agent - all cause the water to leave the crystal structure with more ease, because the gaseous state (and/or being bonded to the drying agent) require less energy and therefore this are more desirable states for the H2O, and so it leaves the crystal matrix.

Why should the water leave the crystal structure more easily when a nonpolar, hydrophobic solvent is used, without any heating and/or vacuum?

(I always said vacuum + heating + sieves + dessicator, not only sieves alone - didn't I?)

Is there any error or redundance?


indole_amine

Lilienthal

  • Guest
You have to DISSOLVE the hydrate :-S
« Reply #15 on: October 30, 2004, 09:39:00 AM »
You have to DISSOLVE the hydrate, nobody was talking about immersing a solide  ::)

indole_amine

  • Guest
?
« Reply #16 on: October 30, 2004, 04:40:00 PM »

wyndowlicker

  • Guest
Look!
« Reply #17 on: October 30, 2004, 05:39:00 PM »
HEy now,


I'll make this simple.

In situ: Drying LSA in solvent with mole seives.

I'm aware of the normal drying in dissector over drying agents of various types.And/or using a vac oven at a low 45C under hard vacuum.This may or may not be an effective enough way to remove the water molecule.

Question #1 is while using a particulular coupling agent that requires bone dry LSA would drying in a variety of different solvents with mole seives as a drying agent to remove trace H20 be signifficantly effective?Yes or NO?

Question#2 From experience obly who can answer if the drying at 45C for several hours will be effective to aquire bone dry conditions? Yes or no.And why if you have some practical experience.
:P


timnickbear

  • Guest
Drying Lysergic Acid
« Reply #18 on: November 01, 2004, 01:32:00 PM »
Presumably foaf is going to make LSD out of the Lysergic Acid Hydrate.  I believe that most synthesis' use Lysergic Acid Monohydrate as the precursor, however by taking the Lysergic Acid Hydrate you could heat the composition up to it's MP over a series of tempature raises(if purification is needed) and condense with DEA in a reflux setup.

Hieroclasm

  • Guest
salt
« Reply #19 on: November 07, 2004, 09:15:00 PM »