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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
Glucose on reaction with HI gives n-hexane. What does it suggest about the structure of glucose?
What do you observe when glucose solution is heated with Tollen’s reagent?
Write the reaction involved when D-glucose is treated with the following reagent:
(CH3CO)2O
The spatial arrangement of the given molecule is denoted by:
The number of asymmetric carbon atom(s) below the figure is/are
Oxime is formed by treating glucose with ____________.
Which of the following statements is incorrect regarding glucose?
When glucose reacts with bromine water, the main product is ____________.
Glucose is found to exist in two different α and β crystalline forms. These forms can be obtained by:
(i) The α form of glucose is obtained by crystallisation from a concentrated solution of glucose at 303 K.
(ii) The β form of glucose is obtained by crystallisation from a concentrated solution of glucose at 303 K.
(iii) The β form is obtained by crystallisation from hot and saturated aqueous solution at 371 K.
(iv) The α form is obtained by crystallisation from hot and saturated aqueous solution at 371 K.
Reduction of glucose by HI suggest that ____________.
The number of chiral carbon atoms present in cyclic structure α-D(+) glucose:
The two forms of D-glucopyranose obtained from the solution of D-glucose are called ____________.
The letter D and L in carbohydrates represent ____________.
Why does compound (A) given below not form an oxime?
(A)
How will you distinguish 1° and 2° hydroxyl groups present in glucose? Explain with reactions.
Assertion: D (+) – Glucose is dextrorotatory in nature.
Reason: ‘D’ represents its dextrorotatory nature.
Account for the following:
What happens when D – glucose is treated with the following reagents
Bromine water
Account for the following:
What happens when D – glucose is treated with the following reagents
HNO3
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 ______.
