chemrox
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citrates, picrates & oxalates
I'm asking for help making derivative salts of amines that are solid at stp and soluble in slightly polar to non polar slovents. The question is
making the picrates, citrates and oxalates specifically but this kind of derivative in general. I'm assuming one finds a solvent for the amine that
also works for the acid. My oxallic is dihydrate so there's a dehydration issue there too.
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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Elawr
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What kind of amines are you working with?
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chemrox
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I haven't completely worked out the structure. Aromatic with another unsaturated ring attached that is not aromatic. In terms of solubility sort of
like phenylpropanolamine but not a drug as far as I know.. not intended to be anyway. IR indicates a C=O present an monosubbed phenyl.
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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Panache
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It depends if your amine is liquid or crystalline as the free base. Likewise it depends on the thermal stability of the prepared salt, its solubility
in various solvents and also what type of crystal you are looking for. Drug companies have much vested in these types of questions because depending
on the salt some physical properties of the bulk material can be manipulated, such as flowability, compressability etc.
In my opinion, grind the free base with correct amount of counter acid until it is a dry powder. Then add a small amount of water to make a slurry,
grind some more and more, evaporate the water slowly in a 50C oven or dessicator. Store in a covered but open container and observe signs of yellowing
or other physical changes as an initial assessment as to the stability of the salt and its deliquescence.
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Elawr
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Indolamines?..such as melatonin, serotonin, or tryptophan?
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Klute
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See my post on oxalates, from dehydrated oxalic acid. I think the same methodology can be applied to picrates and citrates, as long as you find a
solvent in which the amine and the acid is soluble in, like methanol or IPA. Dissolve your acid in the alcohol, then add stoechiometric amount of
freebase dropwise. You can dissolve you freebase in a non poalr solvent such as toluene to minimize the amount of salt dissolved in the alcohol, then
filter, wash with ether, and dry.
\"You can battle with a demon, you can embrace a demon; what the hell can you do with a fucking spiritual computer?\"
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chemrox
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Klute- what would I do without your encylopedic knowledge ? ;^)
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Mush
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Journal of Molecular Structure
Volume 608, Issues 2–3, 22 May 2002, Pages 123–133
"Oxalates of n-propylamine, n-butylamine, ethylenediamine, 1,4-butanediamine, piperazine, guanidine and 1,4-diazabicyclo[2,2,2]octane (DABCO) have
been synthesized and characterized by single crystal X-ray diffraction and other techniques."
STUDIES IN VAPOR PRESSURE. 111. THE TOLUIDINES
J. F. T. Berliner , Orville E. May
J. Am. Chem. Soc., 1927, 49 (4), pp 1007–1011
DOI: 10.1021/ja01403a017
Publication Date: April 1927
"An excellent separation of the 0- and p-toluidines may be
obtained by means of the formation of the dioxalates of these compounds(2). The o-toluidine dioxalate is considerably more soluble in water and ether
than the corresponding para compound. In fact, the p-toluidinedioxalate
is so insoluble in ethyl ether that a practically complete quantitative separation may be accomplished (3)."
Study of picrate salts with amines
Nidhi Goel a, Udai P. Singh a,⇑, Gurdip Singh b, Pratibha Srivastava b
Journal of Molecular Structure 1036 (2013) 427–438
Spectral investigations of amino acid picrates
j.saa.2005.11.022
Purification of Laboratory Chemicals-Butterworth Heinemann (2012)
"AMINES
Picrates
The most versatile derivative from which the free base can be readily recovered is the picrate. This is very
satisfactory for primary and secondary aliphatic amines and aromatic amines and is particularly so for
heterocyclic bases. The amine, dissolved in water or alcohol, is treated with excess of a saturated solution of
picric acid in water or alcohol, respectively, until separation of the picrate is complete. If separation does not
occur, the solution is stirred vigorously and warmed for a few minutes, or diluted with a solvent in which the
picrate is insoluble. Thus, a solution of the amine and picric acid in ethanol can be treated with petroleum ether
to precipitate the picrate. Alternatively, the amine can be dissolved in alcohol and aqueous picric acid added.
The picrate is filtered off, washed with water or ethanol and recrystallised from boiling water, ethanol,
methanol, aqueous ethanol, methanol or chloroform. The solubility of picric acid in water and ethanol is 1.4
and 6.23% respectively at 20o.
It is not advisable to store large quantities of picrates for long periods, particularly when they are dry due to
their potential EXPLOSIVE nature. Also this method is not advised when large quantities of amines (e.g.
>25g) are to be purified. The free base should be recovered as soon as possible.
The picrate is suspended in an excess of 2N aqueous NaOH and warmed a little. Because of the limited solubility of sodium picrate, excess
hot water must be added. Alternatively, because of the greater solubility of lithium picrate, aqueous 10%
lithium hydroxide solution can be used. The solution is cooled, the amine is extracted with a suitable solvent
such as diethyl ether or toluene, washed with 5N NaOH until the alkaline solution remains colourless, then with
water, and the extract is dried with anhydrous sodium carbonate. The solvent is distilled off and the amine is
fractionally distilled (under reduced pressure if necessary) or recrystallised.
If the amines are required as their hydrochlorides, picrates can often be decomposed by suspending them in
acetone and adding two equivalents of 10N HCl. The hydrochloride of the base is filtered off, leaving the picric
acid in the acetone. Dowex No 1 anion-exchange resin in the chloride form is useful for changing solutions of
the more soluble picrates (for example, of adenosine) into solutions of their hydrochlorides, from which sodium
hydroxide precipitates the free base."
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Mush
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Practical procedures:
https://www.erowid.org/library/books_online/pihkal/pihkal001...
#1. AEM
"The neutral solution was brought to a boil, and clarified by filtration through paper. To the hot filtrate there was added a solution of 8.9 g picric
acid in 100 mL boiling EtOH. The mixture was stirred and cooled, with the formation of a heavy yellow crystalline mass. After standing in the ice tub
for several hours the mixture was filtered, providing 8.0 g of the picrate salt with a mp of 176-181 °C from H2O. A solution of this salt in 300 mL
boiling H2O was treated with 60 mL concentrated HCl. On cooling, there was a deposition of picric acid, which was removed by filtration. The aqueous
filtrate was washed with 3x50 mL nitrobenzene, then with 3x50 mL Et2O. The pH was brought above 9 by the addition of aqueous NaOH, and the filtrate
was extracted with 3x100 mL CH2Cl2. Removal of the solvent from the pooled extracts gave a nearly colorless oil, which was dissolved in 300 mL
anhydrous Et2O and saturated with hydrogen chloride gas. The white crystals of 2-amino-1-(3,4,5-trimethoxyphenyl)butane hydrochloride (AEM) were
removed by filtration, Et2O washed, and air dried. They weighed 4.72 g."
#120 MEDA
" This was filtered free of a small amount of insolubles, and the clear filtrate was heated to 80 °C. To this there was added a solution of 9.2 g
picric acid (90% material) in 100 mL boiling EtOH, and the clear mixture allowed to cool in an ice bath. Scratching generated yellow crystals of the
picrate salt. This salt was filtered free of the aqueous environment, treated with 50 mL of 5% NaOH, and stirred until the picric acid was totally in
the form of the soluble sodium salt. This was then extracted with 3x100 mL CH2Cl2, the extracts pooled, and the solvent removed under vacuum...."
#58 DMMDA
" The aqueous phase was brought to a pH of 6 with Na2CO3. This was heated to 80 °C and clarified by filtration though paper. The addition of a
stochiometric amount of picric acid in boiling EtOH gave rise to precipitation of the product picrate as globs that did not crystallize. These were
washed with cold H2O, then dissolved in 30 mL 5% NaOH. Extraction with 2x75 mL Et2O, and the stripping of the solvent from the pooled extracts, gave
3.1 g of an oily residue..."
#132 MMDA
" The phases were separated, and sufficient saturated aqueous Na2CO3 was added to the aqueous phase to bring the pH up to about 6.0. This was heated
to 80 °C and filtered through a coarse sintered glass funnel to remove some insoluble fines. The clear filtrate was brought up almost to a boil, and
treated with a solution of 10.2 g of 90% picric acid in 110 mL boiling EtOH. Crystals of the picrate formed immediately at the edges, and as the
reaction flask was cooled in an ice tub, the entire reaction set to a yellow mass of crystals. These were removed by filtration, washed sparingly with
80% EtOH, and air dried to give 14.0 g of the picrate salt of MMDA, with a mp of 182-184 °C. Recrystallization of a small sample from EtOH dropped
this to 179-181 °C. This salt was treated with 30 mL 5% NaOH, and the red solution decanted from some insolubles. Additional H2O and NaOH effectively
dissolved everything, and the resulting basic aqueous phase was extracted with 3x50 mL CH2Cl2. The pooled extracts were stripped of solvent under
vacuum, and the residue dissolved in 200 mL anhydrous Et2O and saturated with anhydrous HCl gas...."
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