[Vrig]

I got a real hard time understanding and thus identifying such protons (even chiral centres!).

Sticking to the topic;

http://www.chemistry.ccsu.edu/glagovich/teaching/316/nmr/couplingtopic.html

I understand homotopic protons, I do understand the enantiotopic protons aswell but I don't understand how the last picture on the site (from the link above) give rise to diastereotopic protons.

I see only one difference between the two (if looking at the pictures) and that's the Cl substituted by an alkyl (enentiotopic vs diastereotopic figure).


I do see S/R (from enantiotopic figure) and R/S (the reversed, for diastereotopic) but don't we need to have two chiral centres for something to be diastereoisomer?

Thanks for any help (even on identifying chiral centres and distinguishing between enantiomers and diastereomers  )

/ Confused student

EDIT: Oh and is there such a thing as heterotopic protons (or are "heterotopic protons" a collective name for enantio-/diastereotopic protons?)

[sjb]

I got a real hard time understanding and thus identifying such protons (even chiral centres!).

Sticking to the topic;

http://www.chemistry.ccsu.edu/glagovich/teaching/316/nmr/couplingtopic.html

I understand homotopic protons, I do understand the enantiotopic protons aswell but I don't understand how the last picture on the site (from the link above) give rise to diastereotopic protons.

I see only one difference between the two (if looking at the pictures) and that's the Cl substituted by an alkyl (enentiotopic vs diastereotopic figure).

I do see S/R (from enantiotopic figure) and R/S (the reversed, for diastereotopic) but don't we need to have two chiral centres for something to be diastereoisomer?

Thanks for any help (even on identifying chiral centres and distinguishing between enantiomers and diastereomers  )

/ Confused student

In the last diagram R* is one specific enantiomer. Accordingly, when you replace the protons shown you get diastereromers

[Vrig]

Ah, many thanks for the fast reply and for clearing that up! Any thoughts on "heterotopic protons" or is that just something that doesn't really exist?

[sjb]

Something like http://www.chem.wisc.edu/areas/reich/nmr/05-hmr-08-symmetry.htm ?

[Vrig]

Thank you!!