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All 33 posts Subject: resolution of racemic meth Please login to post Down

zero_nrg
(Stranger)
03-12-04 17:59
No 494663
      resolution of racemic meth

Have been reading through the procedures for seperating a racemic mix of meth into D and L form. The easiest seems to be a procedure from Rusznak. Question: Any reason why toluene, or some other non-polar, should not be substituted for the benzene?

https://www.rhodium.ws/chemistry/amphetamine.resolution.html
A mixture of 0.1 mole (13.52 g.) phenylisopropylamine (or 14.92 g. methamphetamine base) in 60 ml benzene, 0.05 mole d-tartaric acid (7.50 g.) in 30 ml water, and 2 g sodium hydroxide (reagent grade or titrated equivalent) in 3 ml water was kept 4 hours with intermittent shaking, and the organic phase evaporated to give 98% L-phenylisopropylamine. The aqueous phase was extracted with benzene at pH 13 and evaporated to give 96% D-enantiomer

Rhodium
(Chief Bee)
03-12-04 21:57
No 494701
User Picture       Toluene can most often substitute for benzene

I see no reason why you couldn't use toluene instead, but I would not reccommend you to use just any non-polar you have lying around.

^{The Hive - Clandestine Chemists Without Borders}

elfspice
(Newbee)
03-20-04 01:15
No 496236
      benzene bad

a lot of old articles and reports talk about using benzene, it used to be common as hexane and toluene and dcm are now.

... base) in 60 ml benzene, 0.05 mole ... 98% L-phenylisopropylamine. The aqueous phase was extracted with benzene at pH 13 ...

I would think that hexane and the lesser naptha should work too, it looks to me like the principle of the method is you put the right ratio of sodium ions and d-tartaric acid in there, and an ionic equilibrium develops that gradually drives the l-meth into the freebase over a long period of time.

note that 2g of NaOH is 0.0501 moles, so that would read:

A mixture of 0.1 mole (13.52 g.) phenylisopropylamine (or 14.92 g. methamphetamine base) in 60 ml benzene, 0.05 mole d-tartaric acid (7.50 g.) in 30 ml water, and 0.05 (2g) sodium hydroxide (reagent grade or titrated equivalent) in 3 ml water

in short form:

0.1667 mol H₂O + 0.5 mol NaOH
01.667 mol H₂O + 0.5 mol D-Tartaric Acid (grape-sourced tartaric acid)
0.1 mol d,l meth HCl (ie 0.1 mol of HCl molecules in there too)

I think that if they say .1 mol of phenylisopropylamine and 60ml of benzene then they expect that .05 mol of the l isomer will happily dissolve into it. in this described procedure they are more or less saying ~6.5g of l-amphetamine in 60ml of benzene... that's a lot of stuff dissolved in there... i think if you use toluene probably 50% extra volume of solvent and hexane maybe twice as much. somebee with more experience than me can suggest appropriate differences, most expert cooks would know how much is enough toluene per gram of meth to dissolve it.

i understand there would be a way to then extract that l-meth into acid solution and then it can be isomerised into racemic again and the separation done again. I would think that the 3rd or 4th time would have the majority of it out... this would in effect approximately 150% increase the effect of the stuff, lower the doses needed etc etc.

barkingburro
(Hive Bee)
03-22-04 16:57
No 496653
      i have a better question

why do you want to seperate the two? swibb has had very very good results from a 1/3 - 2/3 and 1/4 - 3/4 mix of meth. l and d respectively. swibb's 'personal' is generally of te mixed variety

zero_nrg
(Stranger)
03-31-04 20:22
No 498330
      percentages obtained

Barkingburro: how would one obtain a 75/25 mix of D/L (or any other ratio besides 50/50) if the racemic mix was not seperated first? Also, based on recent experience, I am not sure if a racemic mix crystalizes like pure D (and probably L-but I have not tried it). My limited experience with this is that of charliebrown in post Post 460635 (charliebrown: "kinetics of racemic meth crystallization", Stimulants) where the mix just crystalizes all at once into very small crystals (note exception below). Would it make sense that a racemic mixture could not form large crystals as the isomeric configurations in space are different for D and L ?
Another question, after gassing a batch of racemic freebase in toluene the crystals were vac filtered and the mother liquor poured back into the beaker where the base was originally gassed. There was perhaps a gram of tiny white crystals floating around in the toluene and the toluene was again gassed with HCl to preciptate more crystals if any. Not only did no more crystals precipitate, but the ones that were floating around in the toluene disappeared into the toluene. No matter, just left the beaker sitting in the sink as the remaining crystals were not worth the effort to recover. After approx. 24 hrs looked at this beaker again and to my surprise the most gorgeous absolutely clear crystals had formed on the bottom of the flask. Not huge crystals but certainly larger than than the tiny white crytals originally swimming around in the toluene. The gas was generated with H2SO4 on NaCl and equipped with calcium chloride drying tube which was removed not too long after the gassing procedure started (clogged up). Could water be responsible for the disappearance of the tiny white crystals in the toluene which then precipitated as the liquid cooled after any non-polar crap was solvated by the toluene? The original reduction on P2P with NaBH4 via the Labtop dry method. -zero

barkingburro
(Hive Bee)
04-04-04 21:45
No 499058
      not an expert but

it has appeared to swibb that the d and l isomers x-talize in different layers in ice cold anyhydrous ipa. which is which swibb is not really sure of, but one seems to make a longer flat rectangle of a xtal and the other is more like a cubish xtal. the cubish xtals come out looking kinda like a q-bert board and the others kinda like 2x4's.

swibb was also assuming that u had a single batch of racemic with a known % mixture and could then adjust ratio by adding additional 100% d-. not trying to come across as an expert in seperation just wonderin y go through the trouble

Rhodium
(Chief Bee)
04-04-04 23:35
No 499084
User Picture       no spontaneous isomer separation

No, spontaneous isomer separation rarely happens. Either it is two different crystal shapes (less likely) or an impurity (more likely).

^{The Hive - Clandestine Chemists Without Borders}

zero_nrg
(Newbee)
04-28-04 18:26
No 503558
      Louis Pasteur used a micrscope and tweezers to

Louis Pasteur used a micrscope and tweezers to seperate racemic tartaric acid into the D and L form. Those crystals must be very different in their geometry which, as Rhod indicates, is rare. -zero

Rhodium
(Chief Bee)
04-28-04 19:15
No 503576
User Picture       To be precise, it was sodium ammonium tartrate

[Louis Pasteur] discovered that sodium ammonium tartrate crystallizes in two enantiomorphic forms. After mechanical separation of the different crystals, using tweezers under a microscope, their aqueous solutions rotated polarized light into different directions! The grand old man in the field of optical rotation, Jean Baptiste Biot (1774-1862), insisted that Pasteur had to repeat his experiments in public. Pasteur was successful because two fortunate circumstances worked together. First, he had selected sodium ammonium tartrate which is one of the very few salts of tartaric acid that forms enantiomorphic crystals which can be separated manually; second, he did his crystallization at temperatures below 26°C (79°F); at higher temperatures, only the racemate crystallizes.

Taken from Journal of Receptor and Signal Transduction Research 19, 15-39 (1999) (http://home.t-online.de/home/kubinyi/chanc-tx.pdf)

^{The Hive - Clandestine Chemists Without Borders}

zero_nrg
(Newbee)
06-06-04 19:44
No 511818
      seperation anxiety

Excuse my general chem. and A/B ignorance, but regarding the Rusznak procedure above, can anyone say definitively whether the freebase or the HCl is used in the procedure? If the HCl is used, as elfspice indicates, why is the weight given for the freebase? Also, I´m assuming that " (or 14.92 g. methamphetamine base) in 60 ml benzene" means to dissolve the freebase in the benzene (doubt the HCl dissolves in benzene). Molar equivalents of D-tartaric acid and NaOH will react to form a salt (tried this last night to satisfy my curiosity). So even if the freebase were more reactive wouldn´t the D-tartaric acid first react with the NaOH to form a salt simply because they are in the same phase? If the tartaric acid did react with the FB first, wouldn´t it just be liberated by the basic conditions in the aqueous layer and float up with the benzene? When I first read this procedure I thought that the write-up was just sloppy and what was meant was to take the FB dissolve it into the benzene, add the tartaric acid in water, wait and shake 4 hrs, seperate in funnel, now use the 2 grams NaOH in 3 ml H2O to liberate the D-freebase which dissolved into the aqueous layer as it reacted with the acid. Very confused. -zero

Rhodium
(Chief Bee)
06-06-04 23:50
No 511856
User Picture       the freebase should be used

Elfspice incorrectly assumed that the NaOH was added to the solution to freebase the added amine hydrochloride. It is not. The freebase amine is to be used, and the purpose of the NaOH is to make the monosodium salt of the tartaric acid (which is a dicarboxylic acid).

In solution, the monosodium d-tartrate then preferentially forms a water-soluble salt with d-methamphetamine while the l-methamphetamine (still remaining in its freebase form) can be extracted with a non-polar solvent.

The reason all this happens is that because of the molecular shape of d-tartaric acid is such that in solution it fits better together with d-methamphetamine than with l-methamphetamine, given a choice (but will freely form a salt with both forms if enough acid is present, therefore one carboxylic acid group on each tartaric acid molecule is 'disabled' by the addition of one equivalent tof NaOH).

latest addition (06-13-04): A stereoisomeric confusion by me corrected above (thanks for spotting it, bio!).
I incorrectly assumed that the preferentially formed salt was l-meth d-tartrate (as this is the salt isolated in many resolutions through fractional crystallizations). The correct interpretation of Rusznak's procedure has been entered above.

Also, note the following important discrepancy between the isomer designations:

The dextro isomer of tartaric acid is the d, (+), L or S isomer; the levo isomer is the l, (-), D or R isomer.
The dextro isomer of (meth)amphetamine is the d, (+), D or S isomer; the levo isomer is the l, (-), L or R isomer.

^{The Hive - Clandestine Chemists Without Borders}

zero_nrg
(Newbee)
06-07-04 01:53
No 511873
      Thanks Rhod, have two more questions: would it

Thanks Rhod, have two more questions: would it make sense to react the NaOH with the D-tartaric acid before adding it to the freebase in benzene? Also, why doesn´t the NaOH react with both carboxylic acid groups on some tartaric acid molecules? Appreciate your insight. -zero

Rhodium
(Chief Bee)
06-07-04 03:26
No 511878
User Picture       monosodium tartrate equilibrium

I'd think it would be best to stick to the procedure as is, i.e. prepare the monosodium tartrate in situ.

The reason no disodium tartrate is formed is that the remaining carboxylic acid group becomes less acidic when monosodium tartrate has formed, so at equilibrium the result will be a solution containing only monosodium tartrate, because if a disodium tartrate molecule meets a free tartaric acid molecule, they'll immediately react to form two molecules of monosodium tartrate.

^{The Hive - Clandestine Chemists Without Borders}

Rhodium
(Chief Bee)
06-09-04 13:47
No 512390
User Picture       O,O'-Dibenzoyl-R,R-Tartaric Acid Meth Resolution
(Rated as: excellent)

_{Optical Resolution in Two Immiscible Solvents in the Presence of an Intermediate Solvent}
Optical Resolution of Methamphetamine by O,O'-Dibenzoyl-R,R-Tartaric Acid in Dichloroethane-Water-Methanol Solvent System
David Kozma and Elemer Fogassy
Synthetic Communications 29(24), 4315-4319 (1999) (https://www.rhodium.ws/chemistry/meth.resolution.di-bz-tartrate.html)

Abstract
A new optical resolution method was developed by the use of a two phase three component solvent system and demonstrated on the example of the resolution of the N-methyl-amphetamine with O,O'-Dibenzoyl-R,R-tartaric acid. By adding methanol as an intermediate solvent to the two phase water-dichloroethane solvent system the solubility and the optical purity of the precipitated salt can be adjusted in wide ranges. By this way a highly efficient one step resolution process can be accomplished.

^{The Hive - Clandestine Chemists Without Borders}

bio
(Hive Bee)
06-12-04 05:02
No 512915
      isomerization method

Now that I have all this L meth piling up an isomerization procedure is needed that is preferably simple and has a high conversion ratio.

Once tried long ago a method from a Helvita Chimica Acta article from the 1920's, maybe Emde's stuff. It was very brief and supposed to convert a pure isomer of ephedrine into an equal percentage racemic mixture......... Heat at 100 C degrees in a sealed tube with 25% HCl for 60 hours............ Simple as that if memory serves me correctly. I did it, but realized too late that my starting ingredient was really not the pure enantiomer and abandoned the project after that.

So the question is.......would this work for methamphetamine? A german bee should be able dig up the HCA article or is there another way quicker, could hardly be easier. Also I remember at the time why 25% HCl and not the 37% ?

Rhodium
(Chief Bee)
06-12-04 17:23
No 513002
User Picture       Some racemization confusions cleared up

Now that I have all this L meth piling up an isomerization procedure is needed that is preferably simple and has a high conversion ratio.

UTFSE. It's also in the Stimulants Forum FAQ.

Once tried long ago a method from a Helvita Chimica Acta article from the 1920's, maybe Emde's stuff. It was very brief and supposed to convert a pure isomer of ephedrine into an equal percentage racemic mixture......... Heat at 100 C degrees in a sealed tube with 25% HCl for 60 hours...

It won't produce racemic ephedrine, it rather converts L-ephedrine to an equal mixture of L-ephedrine and D-pseudoephedrine (or D-ephedrine to an equal mixture of D-ephedrine and L-pseudoephedrine). This corresponds to racemizing the alcoholic chiral center while leaving the amine chiral center untouched.

Acids will not produce DL-Ephedrine regardless of how you do it, for that you need to use a strong base: Post 480374 (Rhodium: "Racemization of Optically Active Ephedrines", Stimulants)

So the question is.......would this work for methamphetamine?

No, the procedure is specific for amino alcohols, not simple amines.

A german bee should be able dig up the HCA article or is there another way quicker, could hardly be easier.

With TFSE you will find that I have already posted Emde's articles in this forum: Post 401416 (Rhodium: "Hermann Emde's Ephedrine Chemistry Treatise", Stimulants)

Also I remember at the time why 25% HCl and not the 37% ?

I assume that using a higher concentration will result in some of the ephedrine being converted to chloroephedrine.

^{The Hive - Clandestine Chemists Without Borders}

Rhodium
(Chief Bee)
06-13-04 00:27
No 513053
User Picture       Please note that

I have made an important correction and addition to Post 511856 (Rhodium: "the freebase should be used", Stimulants)

^{The Hive - Clandestine Chemists Without Borders}

Rhodium
(Chief Bee)
10-05-04 01:49
No 534472
User Picture       Pope-Peachey Optical Resolution of Meth
(Rated as: good read)

Study of the Mechanism of the Optical Resolution of N-Methylamphetamine via Diastereoisomeric Salt Formation by the Pope-Peachey Method
David Kozma, Zoltán Madarász, Maria Acs and Elemér Fogassy
Tetrahedron Asymmetry, 5(2), 193-194 (1994) (https://www.rhodium.ws/pdf/meth.chiral-sep.pope-peachy.pdf)

Abstract
During the optical resolution of racemic N-methylamphetamine by half an equivalent of R,R-tartaric acid in the presence of half an equivalent of hydrochloric acid the tartrate salt of the R-base precipitates with a low optical purity. The optical purity of the precipitated salt is increased by enantiomer exchange between the solid and solvent phase.

^{The Hive - Clandestine Chemists Without Borders}

dwarfer
(esoteric)
10-05-04 21:47
No 534588
User Picture       Unsubstantiated separation technique

[534585]

It is my opinion that at least two isomers of
MethAmphetamine can be separated in great degree
by a technique discovered serendipitously while
doing as described in the referenced thread.

In my mind it even makes sense that the re-precipitation
temperature would be separate among the isomers, since
the melt temperatures are.

The technique, if valid, works best if the isomers are
visually distinguishable from one another in conformation.
(otherwise you would have to keep a close eye on the thermometer.)

_{<<Marve is looking for the MP for the (-)- MA.HCl if anybody knows..} crazy

dwarfer

methyl_ethyl
(Guardian)
10-06-04 01:02
No 534607
User Picture       crossed polaroids

Louis Pasteur used a micrscope and tweezers to seperate racemic tartaric acid into the D and L form. Those crystals must be very different in their geometry which, as Rhod indicates, is rare. -zero

More than likely the separation was done not based on visible differences in crystal geometry, however done through separation of visible crystals through crossed polaroids.

I have never actually tried separating crystals using crossed polarized light microscopy, however I think that it could be done. When looking through a properly set up microscope utilizing crossed polarized optics it is possible (depending on which way your polarizer is set up) to only view dextrorotary, or the levorotary crystals i.e. turning the polarizer over the light source at 90° angles from each other, unless the crystals are birefringent, they will only be visible at one of the two poles, thus making a fairly easy separation. For example all of the visible crystals viewed under the initial pole could be moved toward one side of the microscope field. Then rotate your polarizer 90° and move all of the visible crystals to the opposite field. After a few repetitions of this all crystals will be seperated according to their visibility under crossed porlarization.

Now we have two groups of crystals separated by their visiblility under crossed polaroids. I believe it is not possible to know at this point which "pile" of crystals is d- or l-, however you do know that these piles are opposite to one another as far as rotation is concerned, thus a solution of the crystals should be analysed via spectropolarimetry in order to determine which is d- and which is l-.

If I have time, (ha ha) it would be a nice to re-create this experiment and post some pictures. I used to be very intrigued by crossed polarization microscopy and spectropolarimetry, although very simple concepts, it is quite amazing what the data generated can tell you about the molecule that you are analyzing. Then again I am easily amused, wink

regards,

methyl_ethyl

   Unipolar Mania, It's good for life... laugh

hypo
(Balanced Ego)
10-06-04 07:29
No 534646
      why?

> More than likely the separation was done not based on visible differences in crystal
> geometry, however done through separation of visible crystals through crossed polaroids.

why?
it should be very easy to separate crystalls in right and left handed ones.
(just like you would be able to separate gloves for the right and for the left hand)

"And you for sure cant read nor write assembler, idiot." - orgy.

methyl_ethyl
(Guardian)
10-06-04 22:56
No 534749
User Picture       not sure what you mean

why? it should be very easy to separate crystalls in right and left handed ones. (just like you would be able to separate gloves for the right and for the left hand)

I have no idea what you mean by this, in fact you do not even sound like yourself hypo wink

My point is under crossed polaroids you will only see in your microscopic field either the d- or l- crystals depending on which way the polarizer is set up.

This makes separating the crystals much easier, than if you had all of the crystals visibly present in your microscopic field and were trying to separate individual crystals based on their geometry.

Take the glove scenario for example, it may be easy to seperate 100 pairs of gloves by looking at the way the fingers are arranged. But it would be even easier if you put on a pair of glasses that "filter" out all of the left handed ones. With these spectacles you can just grab any glove that is visible to you, knowing that you are only grabbing the right handed ones. In essence this is what crossed polaroid microscopy would do in this case (theoretically).

regards,

methyl_ethyl

   Unipolar Mania, It's good for life... laugh

Jacked
(Ancient Alchemist Delux)
10-07-04 06:29
No 534796
      reply

Damn I'd hate to be the guy sitting there separating crystals under a microscope for a living.
Just how would he keep from dragging what he cant see with the ones he can see to one side or the other? In other words how does the guy seeing only left handed gloves keep from accidentally moving a right handed glove along with it because its hidden from his view?
How would this polar filter see a raceamized materal?

Tighten Up! (UH)

dwarfer
(esoteric)
10-08-04 00:11
No 534875
User Picture       ignored again.. Snif.

If you shine a plane polarized light on the crystals,
you can dispense with the polarized spectacles..

anyway,

Hmf!: Ignored again.

Damn.

Consider a “Brownian Rachet”
etched in silicon for separation of the isomers.

Although I can’t find it
after 10 minutes of looking at Rhode’s site,
there is a crystalline difference
in the (S)-(+) and the (R)-(+) as I recall,
whihc should be
amenable to the approach..

As regards the (s)-(-) isomer,
if anyone has the MP and other
conformational data, it would be
appreciated.

Also, if my speculation about temperature dependant precipitation/flocculation in stirred
poor solvency liquids is bunk, please advise. crazy

dwarfer

hypo
(Balanced Ego)
10-08-04 09:40
No 534944
      eh..., sorry for being so unclear

of course i wasn't suggesting that it's easier to go by geometric
criteria. my point was that it's definitely possible given the right
crystall system and i'm pretty sure that it's what louis pasteur did.

note that this was 1849 and what they called microscope was probably a
better magnifying glass...

"And you for sure cant read nor write assembler, idiot." - orgy.

indole_amine
(Hive Bee)
10-09-04 10:49
No 535028
User Picture       either way round...

note that this was 1849 and what they called microscope was probably a
better magnifying glass...

Which makes a perfect reason against separation by geometrical appearance ("left-handed crystals"? Visible with pro-grade, adjustable magnifying glasses? How do d- and l-meth crystals differ in appearance? Why does a racemic crystal modification exist then? smile ).

But even with a good magnifying glass and cross polarized light and/or filters you can differentiate very well between the different isomers by view...

Your point is (although originally, you said something else smile ) that due to lack of good optic instruments, Louis Pasteur worked just based on the performance of these, and distinguished isomeric crystals just by view?

Sorry, but I don't get your point...

It is not possible to differentiate between optically pure isomeric d- and l-crystals unless their crystalline structure differs substantially, which is very uncommon as Rhod pointed out earlier.
Very possible (and applicable to every optically active salt!) on the contrary is the visualization of either the optically active (think about it) d- or l-isomer by simply irradiating with polarized light (a filter permitting only photons swinging up/down or left/right to pass, you know it). And the crystals aren't invisble with the "wrong" polarization: they just appear transparent, whereas the other isomer will appear whitish due to reflecting the light rather than letting it pass. All this assumed you figure out how to make most of the d- and l-salt visible at once: with using two contrary polarized light sources (with different wavelengths?) for example, and varying their positions/angle until you get a satisfying distribution of two differently colored crystal subsets, each consisting of mainly one isomer. You surely are aware of that too (as well as about the fact that it surely ain't got anything to do with entropy in this case wink )...

And Pasteur knew it too, I would guess...

_{indole_amine}

"Hypo loves left-handed crystal structures!" laugh

hypo
(Balanced Ego)
10-09-04 12:03
No 535031
      check your facts...

> Which makes a perfect reason against separation by geometrical appearance

on the contrary. try separating crystals with tweezers under 20x and 1000x
magnification. my point was:
a) they did not have microscopes with all those fancy polarisation filter features
b) those crystals were rather big, ie. you could handle them with tweezers, so
you could watch them from all sides, which makes this rather easy. (funny sidenote:
i've seen my highschool teacher make a tiny hexagonal crystal stand on the small
side under a microscope. wow.)

> It is not possible to differentiate between optically pure isomeric d- and l-crystals
> unless their crystalline structure differs substantially, which is very uncommon as Rhod
> pointed out earlier.

well, tartaric acid
a) crystallises in pure d- and l- crystals
b) those crystals are handed
and no they don't "differ substantially", they are like mirror images.

but hey, don't take my word for it:
http://www.worldhistory.com/wiki/L/Louis-Pasteur.htm
Pasteur noticed, upon examination of the tiny crystals of tartaric acid, that the crystals came in two asymmetric forms that were mirror images of one another. Tediously sorting the crystals by hand gave two forms of tartaric acid: solutions of one form rotated polarised light clockwise, while the other form rotated light anticlockwise.

or from the horse's mouth:
http://web.lemoyne.edu/~giunta/pasteur60.html
I carefully separated the crystals which were hemihedral to the right from those hemihedral to the left, and examined their solutions separately in the polarising apparatus.

thanks for trying anyway...

"And you for sure cant read nor write assembler, idiot." - orgy.

WizardX
(Wizard Master)
10-09-04 13:20
No 535036
User Picture       R(+)- AND S(-) Resolution

http://www.orgsyn.org/orgsyn/prep.asp?prep=cv5p0932 R(+)- AND S(-)-a-PHENYLETHYLAMINE

http://www.orgsyn.org/orgsyn/prep.asp?prep=CV9P0387 Part C.

http://www.orgsyn.org/orgsyn/prep.asp?prep=v76p0023 Part C to D.

indole_amine
(Hive Bee)
10-09-04 17:25
No 535054
User Picture       maybe check your intention?

OK, I'll try to make it short smile :

-It begins with this post: Post 503558 (zero_nrg: "Louis Pasteur used a micrscope and tweezers to", Stimulants) and a followup article posted by Rhodium...

-Methyl_Ethyl a few posts later mentions the use of 2 crossed polarized light sources to distinguish between l- and r-isomeric salts as being superior to the mechanic separation by hand.

-Then you question the use of crossed polarized light with the following words: "why? it should be very easy to separate crystalls in right and left handed ones. (just like you would be able to separate gloves for the right and for the left hand)"

-Then Methyl_Ethyl explains to you that it just is the superior method.

-You answer with (drumroll) "i wasn't suggesting that it's easier to go by geometric criteria" (tadaa - sounded like you at least suggested it "should be very easy", though...), and clarify about having meant that mechanical "per view" separation is possible with some salts, and that Pasteur used this technique. As "proof" you give the bad quality of his microscope..

(there's no logic behind that - it is in fact a proof for crossed polarized light isomer identification and against mechanical sorting at that time, if you think about it...)

Nothing new so far...

-Now I tried to explain that polarized lighting has the advantage of being applicable to all optically active salts (not only tartaric, but also visually not distinguishable hydrochlorides of optically pure d/l-isomers for example). To do so, I explained how polarimetric identification with 2 crossed light sources works.

-You claim that I said something wrong and present hexagonal crystals standing on their small side as an argument. You say that with big crystals, mechanical separation is easy and that tartric acid gives distinguishable crystal modifications (D'oh!)..

OK let me reiterate what I said before in four short sentences:

-crossed polarized light identification is more generally applicable and therefore advantageous compared to visual/manual separation with microscope/tweezers.
-Although seeming not in agreement with what I said, you still have given no reasonable exp. about which novel information you originally wanted to add to this thread?!
-It was already said that tartaric gives crystals with differing physical properties,
-and it was already mentioned that Louis Pasteur used the tedious "by hand" method on tartaric.

So far the important facts I re-checked....

"thanks for trying anyway..."

Well, you're welcome - even more if you try to understand what others write next time, before criticizing them... wink

(dividing a bunch of salt into optically pure isomeric salt modifications by hand can be a good occupation for the long winter months - hypo sittin there with his giant magnifying glass and a needle, while others just illuminate the scene correctly, take what they want and leave back the remainder - but hey! it's your time...)

_{indole_amine}

"Hypo loves left-handed crystal glove structures!" wink

hypo
(Balanced Ego)
10-09-04 18:22
No 535060
      you're the one who needs reading lessons.

1) there was a misunderstanding between me and methyl_ethyl: i thought
she was saying that louis pasteur used polarised light.
2) the misunderstanding was cleared up by me saying that i was only talking
about pasteur and _nothing_ else.
3) you answered to that post adding "And Pasteur knew it too, I would guess..."
making clear that you are talking about pasteur too.
4) you were as usual wrong and have the cheekiness to sneak out of the situation
by misrepresenting facts.

> tadaa - sounded like you at least suggested it "should be very easy", though...

read the whole sentence. i said "very easy given the right crystal system".

> You claim that I said something wrong and present hexagonal crystals standing on
> their small side as an argument.

what? i added that as funny sidenote. this is _not_ presenting something as an argument.
it's becoming pretty obvious that you have a language problem and don't understand what
you are reading.

> To do so, I explained how polarimetric identification with 2 crossed light sources works.

nobody cared, because we knew it already. you just wasted bandwith as usual.

> while others just illuminate the scene correctly, take what they want and leave back the remainder

go ahead, i will make some diastereomer salt with an enantiomeric pure acid and
chromatography the shit. let's see who is the first to separate 10g of product. tongue

"And you for sure cant read nor write assembler, idiot." - orgy.

indole_amine
(Hive Bee)
10-09-04 20:44
No 535078
User Picture       and so CUTE...

Hypo: I still fail to see your intention!

"1) there was a misunderstanding between me and methyl_ethyl: i thought
she was saying that louis pasteur used polarised light.
2) the misunderstanding was cleared up by me saying that i was only talking
about pasteur and _nothing_ else."

So you originally thought Methyl_Ethyl was talking about something, and so you started to ramble; but then you realized that you were wrong, and therefore you "cleared up the misunderstanding" by saying that at least YOU raised the issue?
Strange, at this point my understanding of your motivation becomes drastically diminished... smile

And "talking about Pasteur and _nothing_ else" is inappropriate as a reply to "I know a technique superior to that of Pasteur's: using crossed polarized light..."

And please don't complain about wrong citations of posts you just edited a few seconds ago...

My comments on the sentences you waste our precious bandwidth with (as usual)...

1) your problem if you misunderstand things, no need to start an argument, hm?

2) well of course you said different things; besides telling us about which method Pasteur used, you also said "my point was that it's definitely possible given the right crystall system" - and that's fine dude. Because noone has ever doubted this. No need to become angry...

3) Yeah, and I meant that Pasteur surely knew too about his separation method being only applicable for optically active salts with big crystal size. So what about it?

4) Sure, I forgot - I is me, and you is HYPO, of course I must be wrong...
(could you please show me where I am actually wrong?)

"what? i added that as funny sidenote. this is _not_ presenting something as an argument. it's becoming pretty obvious that you have a language problem and don't understand what you are reading"

Nobody cared, because we knew it already. you just wasted bandwidth as usual.

"nobody cared, because we knew it already. you just wasted bandwith as usual."

It is becoming pretty obvious that you have an ego problem and don't know when to admit having said something wrong...

(Why do you always become insultive if you can't prove yourself right - have had bad experiences during your childhood maybe? wink )

"go ahead, i will make some diastereomer salt with an enantiomeric pure acid and chromatography the shit. let's see who is the first to separate 10g of product"

OK, at last you agree with the tediousness of manual separation (although you promoted it originally wink ). Chromatography might be indeed the most practical way to go.

(Finally! hypo as we know him is back! Your unusual lack of logic/sqeamishness almost started to seriously worry me... smile )

_{indole_amine}

hypo
(Balanced Ego)
10-09-04 21:42
No 535089
      doh!

> Hypo: I still fail to see your intention!

the intention was to get historical facts straight:
pasteur used geometric properties, not polarised light.

reread this post, everything is cleared up therein: Post 534944 (hypo: "eh..., sorry for being so unclear", Stimulants)

> And please don't complain about wrong citations of posts you just edited a few seconds ago...

are you insane? which post did i edit, apart from spelling fixes?
what citation did i complain about?

> could you please show me where I am actually wrong?

at your service! this post: Post 535028 (indole_amine: "either way round...", Stimulants)
highly implies that pasteur used polarised light to separate the crystals. wrong.

> Why do you always become insultive if you can't prove yourself right

the funny thing is that in our discussions so far i have always been right, as
has been confirmed by other bees, and you always feel offended for no reason.

> don't know when to admit having said something wrong...

i have no problem admitting that. but i don't see anything by me in this thread
that was wrong or not coherent.

> OK, at last you agree with the tediousness of manual separation

i've never said anything different. too bad that you're not capable of understanding the
english language.

"And you for sure cant read nor write assembler, idiot." - orgy.

Rhodium
(Chief Bee)
11-01-04 23:55
No 539130
User Picture       Methamphetamine Tartrate Resolution Theory
(Rated as: good read)

Calculation of the Efficiency of Optical Resolutions on the Basis of the Binary Phase Diagram for the Diastereoisomeric Salts
Dávid Kozma, György Pokol and Mária Ács
J. Chem. Soc. Perkin Trans. 2 435-439 (1992) (https://www.rhodium.ws/pdf/meth.tartrate.resolution.pdf)

Abstract
ln resolutions based on the solubility difference between pairs of diastereoisomeric salts, the maximum efficiency (parameter S) can be calculated from a knowledge of the eutectic composition of the binary T-x diagram. We demonstrate that an approximate binary phase diagram can be determined from the DSC melting curve of a single diastereoisomeric salt mixture, namely the global 1:1 mixture of diastereoisomeric salts isolated from a resolution without separation. Data estimated with the reported method are compared to the experimental results of seven resolutions. The method has proved to be efficient for diastereoisomeric salt systems forming crystalline conglomerates. Comparison of calculated S values obtained from a single racemic substrate with different resolving agents facilitates selection of the best resolving agent in the set.

^{The Hive - Clandestine Chemists Without Borders}

	https://the-hive.archive.erowid.org	the-hive@erowid.org



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