Talk:Epimer

I changed the "chiral carbon centers" to stereogenic centers, as chiral center is an incorrect term, and other elements than carbon can also display assymetric substitution patterns (for instance phosphorous, nitrogen, sulfur) According to some textbooks like morrison boyd epimers differ in configuration at c-2 position as these epimers form same osazone.So there should be some consideration given to this exclusiveness about anomers and epimersApes2005 (talk) 12:56, 29 March 2010 (UTC)

Comment
Example 1. Carbon compounds with only 1 chiral center would have 2^1 = 2 stereoisomers, itself and its mirror image, but no epimers or diastereomers.

Example 2. Carbon compounds with 2 chiral centers would have 2^2 = 4 stereoisomers, itself and its mirror image (with both carbons changed). There would be 1 epimer (with 1 carbon changed) and its mirror image, which would also be an epimer to the original compound. There would be no new diasteriomers. Epimers are a sub-class of diasteriomers having at least 2 chiral centers but only one changed.

Example 3. Carbon compounds with 3 chiral centers would have 2^3 = 8 stereoisomers, itself and its mirror image (with all three carbons changed). There would be 3 different epimers each with a different change at only 1 chiral center compared to the original. Each epimer would have a mirror image, all 3 would be a diasteriomer of the original compound, (with 2 chiral centers changed). There would be no new diasteriomers.

Example 4. Carbon compounds with 4 chiral centers would have 2^4 = 16 stereoisomers, itself and its mirror image (all 4 carbons changed). There would be 4 different epimers, each with a different change at only 1 chiral compound compared to the original. Each epimer would have a mirror image; all 4 would be a diasteriomer, (with 3 chiral centers changed) compared to the original. There would be 3 new diasteriomers, (with 2 chiral centers changed) plus their 3 mirror images, also diasteriomers to the original)

Example 5. The expansion of this series fallows a Pascals triangle design. 1 -- no chiral centers 1 1 --- 1 chiral center and its mirror image. 1 2 1 2 chiral centers (itself, 2 epimers, its mirror image). 1 3 3 1 --- 3 chiral centers (itself, 3 epimers, 3 two-carbon diasteriomers, its mirror image). 1 4 6 4 1 --- 4 chiral centers, (itself, 4 epimers, 6 two-carbon diasteriomers, 4 three-carbon diastereiomers, its mirror image). etc.

131.128.30.15 (talk) 18:07, 9 June 2015 (UTC)gDombi

Request for review
Please review the use of Anomers

Added dispute. to my knowledge Anomers do not have to be Epimers, please help!

Bengt Hennig (talk) 20:40, 2 June 2015 (UTC)

Please put a period after "stereogenic center" and transfer this "other than the last asymmetric carbon atom and anomeric carbon atom." to your elaboration of steroisomers whose difference is not epimeric. Give an example of L and D stereoisomer. Otherwise this is a very good article on a difficult subject. Tdw1203 (talk) 19:05, 8 August 2014 (UTC)

This article could greatly benefit from a review. The text is seemingly confusing and inaccurate. In particular, the introduction is in need of a more elegant definition.

84.215.156.72 (talk) 01:09, 26 March 2014 (UTC)

Axial and equatorial groups, and other topics
I am referring to the following part of the “Examples” section of the article, and related drawings.

"The stereoisomers β-D-glucopyranose and β-D-mannopyranose are epimers because they differ only in the stereochemistry at the C-2 position. The hydroxyl group in β-D-glucopyranose is axial (up from the "plane" of the ring), while in β-D-mannopyranose the C-2 hydroxyl group is equatorial (in the "plane" of the ring). These two molecules are epimers but, because not mirror images of each other, are also not enantiomers (enantiomers have the same name but differ in D and L classification). They are also not sugar anomers, since the wrong carbon is involved in the stereochemistry."

In my opinion, first and most important, with reference to the drawings, the hydroxyl group in β-D-glucopyranose is equatorial (and not axial), while in β-D-mannopyranose the C-2 hydroxyl group is axial (and not equatorial). Am I wrong? Could anybody clarify this point? Second, perhaps the term “wrong carbon” should be clarified.Ekisbares (talk) 08:28, 21 February 2017 (UTC)

Ekisbares (talk) 10:59, 20 February 2017 (UTC)

I did myself the corrections about the first point, no clarification about the same having been provided in the meantime.Ekisbares (talk) 09:08, 23 October 2018 (UTC)

About galactose and glucose
In section "Examples" of the article there is this sentence:

"... In glucose, the -OH group on the first carbon is in the axial position, the direction opposite the -OH group on carbon C-4. In galactose, the -OH group is oriented in the same direction, the equatorial position. In cyclical compounds like these, the -OH group on C-1 may lie in opposite directions, as well". In my opinion, the sentence is not clear, and should be completely reshuffled. In particular, it should be more clearly stated that the main difference between glucose and galactose concerns the -OH group on carbon C-4, which is equatorial in glucose and axial in galactose. Ekisbares (talk) 09:42, 23 October 2018 (UTC)

Epimerization of tesofensine to brasofensine.
It says, "[...] undesired in vivo epimerization of tesofensine to brasofensine." in the article, but they aren't epimers of each other if the diagrams in the articles about each molecule are anything to go by, and therefore they cannot be converted by epimerization from one to the other, surely? Polar Apposite (talk) 20:16, 11 December 2022 (UTC)