Talk:Racemic mixture

Crystallization
Is "Quasiracemate" should be in crystallization (from racemic mixture) section? It is for me a little bit confusing to place it here. I mean, racemic mixture is defined as an equal amount of R and S enantiomers. Quasiracemate refers to co-crystal between two different (but isosteric) chemicals. Crystallization of quasiracemate from racemic mixture implies quaternary phase diagram (R, R', S, S') and to be in the crystallization domain of the RS' or SR'co-crystals. At least we introduce a "quasiracemic mixture" term that I disencourage, I think new section should be created for Quasiracemate.

[Untitled]
Ewen, thanks for starting this article. I've always wanted to know more about isomers. BTW, you can combine an external link with visible text like this:

Compounds with Two Chiral Centers

--Ed Poor

Thanks, Ed. Nice tip: Next, I'll put some graphics in. Actually, I have to go now, but I'll do some more on Tuesday.

Ewen


 * Thanks for stopping by. Somehow, you inspired me to write about Biot-Savart's Law and Jean Baptiste Biot. I'll put in the Chiral Centers link. --Ed Poor

Page Move
Wouldn't be better to have this page named Racemate, and making Racemic the link to it ? --Mykhal 15:48, 1 Jan 2005 (UTC)

I agree, I also suggest creating separate pages for the three types of racemates. --Klusiwurm 17:49, 19 June 2006 (UTC)


 * The 'Racemate' redirects to 'Racemic' already. I can't see any advantage swapping the two pages so 'Racemate' is the main one... Ewen 13:11, 30 November 2006 (UTC)


 * I believe it should definitely be moved because an adjective like "racemic" should not be the title of an article, just like "retarded" (etc) is not an article but redirects to mental retardation. "Racemic mixture" or "Racemate" would either be fine, whichever is more common (the former in my experience). - Draeco 05:24, 13 November 2007 (UTC)
 * Google shows about three times more hits for racemic mixture than for racemate. Since there doesn't seem to be much opposition, I'll make the move. - Draeco (talk) 07:01, 17 November 2007 (UTC)

Question
Is it possible for someone to spell out why some medications sold are "Racemic" and others are only one half of the racemic?. In purchasing the generic of Ritilin, I was sold both methylphenidate and Methylin. One aparently Racemic and the other not. Is there a difference in efficacy? If not, why sell racemic at all? Ed Baker 3 July 2006

There are some laws now that new chiral pharmaceuticals have to be tested for the effects of both enantiomers separately, and maybe they also have to be sold in the enantiopure form - but I'm not too much an expert with these laws. Maybe it also involves restesting old drugs. Apart from that it's a matter of cost, producing a racemate is often cheaper, and even if one enantiomer is inactive producing 50% inactive material might still be cheaper than making 100% active material. I'll try to work on this page somewhen next week, am a bit busy now... --Klusiwurm 08:52, 4 July 2006 (UTC)

Add Thalidomide to the list of pharmaceuticals

Early sentence
This sentence: A racemate is optically inactive: because the two isomers rotate plane-polarised light in opposite directions, a racemic mixture does not rotate plane-polarised light. sounds choppy. I'm not familiar enough with the chemistry to rewrite this sentence, but I think it's saying that a racemic mixture doesn't rotate plane-polarised light because each isomer (each half) rotates the light in opposite directions and thus cancel each other out. But having the same phrase with opposite meanings in the same sentence just sounds bizzare. Reader: "Because it rotates in opposite directions, it does not rotate? But you just said it rotates!" lawlz 82.93.133.130 08:59, 30 November 2006 (UTC)

It means that each isomer in particular have the propery to rotate the plane-polarised light in an opposite direction, but together there's no change. Think it like one isomer rotates the light to the right, and suddenly another isomer rotates the light again to the left, so in theory there's no real change. 2800:810:454:91B7:9451:723:9E67:710E (talk) 16:01, 27 April 2019 (UTC)

Parentheticals
I deleted a speculatory parenthetical ending in a question mark as well as one that started with 'Warning:...' Come on. —Preceding unsigned comment added by 12.214.113.189 (talk) 00:47, 18 October 2007 (UTC)

Kryptoracemic crystals
Citation: The crystallization behavior of (±)-cis-α-[Co(dmtrien)(NO2)2]Cl· 0.5H2O 1 and (±)-cis-α-[Co(dmtrien)(NO2)2]I 2† (dmtrien = 3,6-dimethyl-3,6-diazaoctane-1,8-diamine), Jiwen Cai,  Jozef Myrczek,   Hyungphil Chun and    Ivan Bernal , J. Chem. Soc., Dalton Trans., 1998, 4155-4160 DOI: 10.1039/A806094K 129.132.208.37 (talk) 07:01, 12 July 2014 (UTC)

Why different? The crystals are pure.
''The melting point of the racemic conglomerate is always lower than that of the pure enantiomer. Addition of a small amount of one enantiomer to the conglomerate increases the melting point.''

Why would the melting points be different? All the mixtures consist of pure enantiomer crystals, they are just smaller in the conglomerate. Are interface effects so important to the melting point? 84.227.252.224 (talk) 23:04, 14 October 2014 (UTC)

No, the conglomerate is the only one that consists of crystals of pure enantiomers. It doesn't currently make sense to me that a conglomerate (specifically) would have a different melting point to the separated enantiomers, but I'm willing to hear arguments for it. FlowerFaerie087 (talk) 14:45, 10 April 2015 (UTC)

Yes, the melting temperature of a conglomerate in always lower than the pure enantiomer. The mixture of enantiomerically pure R and S crystals forms a eutectic mixture. Consequently, the melting point is lower (compare to pure enantiomer). It is because the interface effects. I will add a small sentence about it.

Etymology
Can someone add where the word racemics stems from? -DePiep (talk) 16:00, 5 April 2015 (UTC)
 * Its already in the article, "The first known racemic mixture was racemic acid," Christian75 (talk) 19:17, 31 July 2015 (UTC)

Page Merge
Much of the information on this page overlaps with the information on the Racemization page. Since these concepts are interrelated, merging these pages seems to be a logical move. --Jwong61 (talk) 20:36, 1 December 2015 (UTC)
 * One is a class of substances, the other a process. --SCIdude (talk) 15:25, 3 July 2021 (UTC)

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Confusing section
This sentence is very confusing:
 * He manually separated the crystals of a mixture by hand, starting from an aqueous solution of the sodium ammonium salt of racemate tartaric acid

What crystals? I assume (+) and (-) tartaric acid but this is not clear at all. How could he separate the crystals? Again, I have to assume that he separated them by their optical properties. But this section is unreadable if you don't already know that these crystals have different optical properties. And it's not clear why the crystals aren't racemic too. 192.38.103.46 (talk) 15:10, 18 September 2023 (UTC)