Write the reactions of $D-Glucose$ which cannot be explained by its open-chain structure. How can the cyclic structure of glucose explain these reactions?

Vedclass pdf generator app on play store
Vedclass iOS app on app store
(N/A) The open-chain structure of $D-Glucose$ fails to explain the following reactions:
$1$. $D-Glucose$ does not form the hydrogen sulfite addition product with $NaHSO_3$.
$2$. $D-Glucose$ does not give a positive Schiff's test.
$3$. The pentaacetate of $D-Glucose$ does not react with hydroxylamine $(NH_2OH)$,indicating the absence of a free $-CHO$ group.
$4$. $D-Glucose$ exists in two anomeric forms,$\alpha-D-Glucose$ (m.p. $419 \ K$) and $\beta-D-Glucose$ (m.p. $423 \ K$),which cannot be explained by a single open-chain structure.
Explanation by cyclic structure:
These observations are explained by the formation of a cyclic hemiacetal structure. The $-CHO$ group at $C-1$ reacts with the $-OH$ group at $C-5$ to form a six-membered ring (pyranose structure). In this cyclic form,the aldehyde group is involved in hemiacetal formation and is not free to react with $NaHSO_3$,Schiff's reagent,or $NH_2OH$. The existence of two anomers arises due to the formation of a new chiral center at $C-1$ during cyclization.

Explore More

Similar Questions

Carbohydrates are used by the body mainly:

What is the monomer of cellulose?

What are carbohydrates called that cannot be hydrolyzed into simpler compounds?

Match the structures in Row $I$ with their names in Row $II$.
Row $I$:
$(P)$ $\alpha-D-(+)-$Glucopyranose
$(Q)$ $\beta-D-(+)-$Glucopyranose
$(R)$ $\alpha-D-(-)-$Fructofuranose
$(S)$ $\beta-D-(-)-$Fructofuranose
Row $II$:
$(i)$ $\alpha-D-(-)-$Fructofuranose
$(ii)$ $\beta-D-(-)-$Fructofuranose
$(iii)$ $\alpha-D-(+)-$Glucopyranose
$(iv)$ $\beta-D-(+)-$Glucopyranose
Correct match is:

Which of the following equimolar mixtures is known as invert sugar?

Vedclass Products

For Students

Vedclass Test Series

Mock tests in real JEE/NEET style with performance analysis. 5-day free trial.

Start Free Trial
For Teachers

Exam Paper Generator

Generate Set A/B/C/D exam papers from 7.5L+ questions in 2 minutes. 3 chapters free.

Try Free
For Institutes

Online Exam Module

Live online exams with unlimited students, 360° analytics & white-label branding.

See Demo