I am a 12th grader in India. I have understood basic theory on biomolecules. I know about carbohydates (and structures of important saccharides) and $\alpha$-amino acids, proteins, and peptides.

This is a section given in my book:

enter image description here

I understand what is the meaning of "D"-glucose, and also how to identify the functional group. But, notice the last column in this table. I don't understand what they mean by the "typical nature" in each case.

I searched the net but couldn't find anything. Is my book using obsolete/unknown terminology for an existing concept? What is it? Please tell. Thank you!

References: Page 1, Page 2, Page 3

  • 1
    $\begingroup$ Please add the citation to the book, so that it can be viewed in context. $\endgroup$ Dec 1, 2017 at 14:36
  • 1
    $\begingroup$ I never said you should upload any content. I said citation, big difference. Those pages don't really help at all. $\endgroup$ Dec 1, 2017 at 15:19

1 Answer 1


Looks like your book's come up with a "localized" version of the D-L notation.

$\ce{D-L}$ notation in brief: A $\ce{D}$-sugar has the $\ce{-OH}$ group (on the stereogenic carbon atom on the parent chain, furthest away from the aldehyde group) facing right in the Fischer representation. Likewise an $\ce{L}$-sugar has the $\ce{-OH}$ group facing left.

What your book's attempting to do is extend the $\ce{D-L}$ classification to individual carbon atoms in the parent chain.

enter image description here

The "3rd($\ce{L}$)" bit is supposed to mean, "3rd carbon atom has an $\ce{L}$-type configuration".

The "2,3($\ce{L}$)" bit is supposed to mean, "2nd and 3rd carbon atoms have an $\ce{L}$-type configuration".

You can figure out the rest ;-)

This appears to be some sort of memory aid to help you remember the configuration of the various kinds of 6-carbon sugars. The "typical nature" term was, in all likelihood, concocted by the authors (perhaps they thought it sounds better than "mnemonic"?)


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.