Tartrate crystal seeding

Slow Cold Stabilization, Without Tartrate Crystal Seeding... 

These theoretical considerations, applied to a short treatment involving seeding with tartrate crystals, show that great care and strict snpervision is required to ensure the effectiveness of artificial cold stabilization. The following factors need to be closely monitored the wine s initial state of snpersaturation, the particle size of the added tartrates, the seeding rate, the effectiveness of agitation at maintaining the crystals in snspension, treatment temperature and, finally, contact time. 

The rate of y -alumina island formation essentially depends on the nature of the electrolyte used. If outwards migrating (in the terms of Xu et al.102) anions, such as tungstates and molybdates, are used in the anodization process, y- alumina seed crystals are surrounded by pure alumina and crystallization occurs easily. In the case of inwards migrating anions (e.g., citrates, phosphates, tartrates), the oxide material surrounding the y-nuclei is enriched... 

Mechanical Separation of Crystals. The first instance of resolution was by L. Pasteur who was able to resolve crystals of sodium ammonium tartrate (which recrystallizes in two distinct, nonsuperimposable forms below 2TC). Although this procedure is rarely used, one might be able to seed a racemic solution resulting in only one... 

The crystallization procedure employed by Pasteur for his classical resolution of ( )-tartaric acid (Section 5-1C) has been successful only in a very few cases. This procedure depends on the formation of individual crystals of each enantiomer. Thus if the crystallization of sodium ammonium tartrate is carried out below 27°, the usual racemate salt does not form a mixture of crystals of the (+) and (—) salts forms instead. The two different kinds of crystals, which are related as an object to its mirror image, can be separated manually with the aid of a microscope and subsequently may be converted to the tartaric acid enantiomers by strong acid. A variation on this method of resolution is the seeding of a saturated solution of a racemic mixture with crystals of one pure enantiomer in the hope of causing crystallization of just that one enantiomer, thereby leaving the other in solution. Unfortunately, very few practical resolutions have been achieved in this way. 

Werner1 resolved the tris(ethylenediamine)rhodium(III) ion both with sodium-3-nitro-(+)-camphor and with (+)-tartrate as resolving agents. Both methods, however, suffer from disadvantages. The solubility of the diastereoisomer (—)D-[Rh(en) 3] - (3-nitro-(-(-)-camphor)3 precipitated by the first method is so low that purification by recrystallization is impossible. On the other hand, the solubilities of the diastereoisomeric chloride (-b)-tartrates used in the second method are of the same order of magnitude, so that the solution has to be seeded with a crystal of (—)D-[Rh(en)3] Cl (+)-tart -aq. The (+)D form of the chloride (+)-tartrate is not obtained in an optically pure condition. Furthermore, the yields of both methods are low because of the many operations needed for obtaining the stereoisomers of the chloride. By the present method (—)D-[Rh(en)3] + is precipitated as the double salt Li (—)D-[Rh(en)3] (+)-tart 2-3H20, which is purified before conversion to the chloride. The (-bichloride is precipitated from the mother liquor by the addition of hydrochloric acid and ethanol. 

In more recent investigations, Edwards and Smith (40) have carried out further extractions of Picralima seeds, and have found pseudoakuammicine to be optically inactive its 2,16- and 19,20-dihydro derivatives are also optically inactive. Pseudoakuammicine and its two dihydro derivatives have IR-spectra identical with those of the corresponding derivatives of akuammicine hence, pseudoakuammicine is (+)-akuammicine. This conclusion was confirmed by resolution of pseudoakuammicine by fractional crystallization of the (+ )-tartrate. The more soluble salt gave akuammicine, and the less soluble salt gave (+ )-akuammicine, mp 181°-182.5°, [a]f,3° +720° (MeOH). On being mixed with an equimolecular proportion of akuammicine, (+ )-akuam-micine gave pseudoakuammicine. 

In 1902, the unsuccessful fractional crystallization of (— )-aspartate and (-I- )-tartrate salts of the ethylmethyl(a-naphthyl)phenylarsonium ion was reported and, in 1912, the failure to resolve allylbenzylmethylphenylarsonium iodide by seeding solutions of the racemate with crystals of the corresponding optically active ammonium salt was reported . The first evidence of optical activity in arsonium compounds was published... 

There is an obvious connection between crystal chemistry and natural products. Crystals appear in plant material (3,4)—calcium oxalate is extremely common potassium acid tartrate in outer perisperm cells of nutmeg hesperidin and diosmin in cells of many of the Rutaceae calcium carbonate in cells of Cannabinaceae silica in the cells of the sclerenchymatous layer of cardamom seeds. The crystallizing temperature of the solid complex between 1,8-cineoIe and o-cresol forms the basis for official assay of oil of eucalyptus (4). Also worth noting is the fact that alkaloids, particularly brucine, are widely used to resolve optically active acids by diastereoisomer fractional crystallization (5). 

The mini-contact test is based on homogeneous induced nucleation, which is faster than primary nucleation. However, this test does not take into account the particle size of the seed tartrate, although the importance of its effect on the crystallization rate is well known. The operative factor in this test is the surface area of the liquid/solid contact interface. Furthermore, this test defines the stability of the wine at 0°C and in its colloidal state at the time of testing. In other words, it makes no allowance for colloidal reorganization in wine, especially red wine, during aging. 

It should be noted that mini-contact test results tend to overestimate a wine s stability and therefore the effectiveness of prior treatment. This statement is based on work by Boulton (1982). After 2 hours contact, only 60-70% of the endogeneous tartrate has crystallized and therefore the increase in weight of the crystal precipitate is minimized. These results are interpreted to mean that the treatment was more effective, or the wine more stable, than was actually the case. In order to make the mini-contact test faster, more reliable and compatible with the dynamic contact process, the Martin Vialatte Company proposed the following variant in 1984 seeding a wine sample with 10 g/1 of cream of tartar and measuring the drop in conductivity at 0°C. 

This experiment was in fact a rediscovery, several years later, of the work of Gernez (a student of Pasteur) on the crystallization of one of the enantiomeric tartrates from a supersaturated solution by seeding with a pure enantiomeric crystal.This method is known as resolution by entrainment. 

Diastereomer Formation and Isolation Place 15.6 g of (-i-)-tartaric acid and 210 mL of methanol in the Erlenmeyer flask and heat the mixture to boiling using flame-less heating. To the stirred hot solution, cautiously add the solution recovered from the polarimeter and 7.5 g of racemic 1-phenylethanamine. Allow the solution to cool slowly to room temperature and to stand undisturbed tot 24 h or until the next laboratory period." The amine hydrogen tartrate should separate in the form of white prismatic crystals. If the salt separates in the form of needlelike crystals, the mixture should be reheated until a//the crystals have dissolved and then allowed to cool slowly. If any prismatic crystals of the salt are available, use them to seed the solution. 

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