While reading some notes about Glucose and its various projections:

  • Fischer Projection: 4 chiral centres


  • Haworth Projection: 5 chiral centres


My doubt is that is there any (specific) method (practical) to ascertain the number of chiral centres in both the forms.

I know that more than 99.5% of glucose exists as Haworth Projection - Closed Ring Structure and hence Linear - Fischer Projection practically does not exist.

But it (linear ie open chain glucose) could be always isolated though difficult.

Thank you!

  • $\begingroup$ While alpha-D-glucose does primarily exist in the cyclic form, it does not exist as a Haworth Projection since the ring is not planar. The chair conformation is a more accurate description. google.com/…: $\endgroup$ – user55119 Apr 13 '19 at 2:06
  • $\begingroup$ @user55119 : What you say is absolutely correct. But what my point is whether you consider simple closed ring or haworth projection or chair conformer of glucose it would be immaterial while considering the number of chiral centres, which is 5, in comparison to the chiral centre (4) in a linear representation of glucose. chem.libretexts.org .. bottom of this page... $\endgroup$ – glucose Apr 13 '19 at 4:35
  • $\begingroup$ It is just a matter of which representation you are talking about. There is no absolute answer. Fischer used the linear representation to distinguish amongst stereoisomers. It was a simplification of Van't Hoff's more complex representation. $\endgroup$ – user55119 Apr 13 '19 at 15:01

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