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प्रश्न
Write the reactions of D-glucose which can’t be explained by its open-chain structure. How can cyclic structure of glucose explain these reactions?
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उत्तर
Following reactions and facts could not be explained by open-chain structures of glucose.
• Despite having the aldehyde group, glucose does not give 2, 4 − DNP test, Schiff's test and it does not form the hydrogen sulphide addition product with \[\ce{NaHSO3}\].
• The pentaacetate of glucose does not react with hydroxylamine indicating the absence of a free −CHO group.
It was proposed that one of the −OH groups may add to the −CHO group and form a cyclic hemiacetal structure. It was found that glucose forms a six-membered ring in which −OH at C − 5 is involved in a ring formation.
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संबंधित प्रश्न
Draw the simple Fisher projection formulae of D - (+) - glucose and D - (-) - fructose
Enumerate the reactions of D-glucose which cannot be explained by its open chain structure.
What happens when glucose is treated with hydroxylamine?
Glucose on reaction with HI gives n-hexane. What does it suggest about the structure of glucose?
Write the reaction involved when D-glucose is treated with the following reagent:
(CH3CO)2O
Choose the appropriate answer(s) for the below representation from the options given
The symbols D and L represents ____________.
When glucose reacts with bromine water, the main product is ____________.
Glucose reacts with acetic anhydride to form ______.
A solution of D-glucose in water rotates the plane polarised light ____________.
The number of chiral carbon atoms present in cyclic structure α-D(+) glucose:
The letter D and L in carbohydrates represent ____________.
The number of chiral carbons in ß-D(+) glucose is ____________.
Which of the following pairs represents anomers?
On the basis of which evidences D-glucose was assigned the following structure?
\[\begin{array}{cc}
\ce{CHO}\\
|\phantom{....}\\
\phantom{..}\ce{(CHOH)4}\\
|\phantom{....}\\
\phantom{..}\ce{CH2OH}
\end{array}\]
What happens when D-glucose is treated with the following reagent?
HI
Account for the following:
There are 5 OH groups in glucose
Consider the following reactions:
(i) \[\ce{Glucose + R-OH ->[Conc. HNO3] [A] ->[X eq of][(CH3CO)2O] Acetyl derivative}\]
(ii) \[\ce{Glucose ->[Ni/H2] [A] ->[Y eq of][(CH3CO)2O] Acetyl derivative}\]
(iii) \[\ce{Glucose ->[Z eq of][(CH3CO)2O] Acetyl derivative}\]
'X, 'Y' and 'Z' in these reactions are respectively:
Glucose with excess of phenyl hydrazine forms ______.
When D-glucose reacts with HI, it forms ______.
