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प्रश्न
Enlist the properties of glucose that can not be explained on the basis of open chain structure of it
उत्तर
Although the open chain structure of D (+) − Glucose explains most of its reactions, it fails to explain the following facts:
a) D (+)-Glucose does not undergo certain characteristic reactions of aldehydes
eg., Glucose does not form NaHSO3 addition product, aldehyde-ammonia adduct 2, 4 − DNP derivative and does not respond to Schiff’s reagent test.
b) Glucose reacts with NH2OH to form an oxime but glucose pentaacetate does not react
with NH2OH, which implies that the free aldehyde group is absent in glucose pentaacetate
c) D(+)-Glucose exists in two stereoisomeric crystalline forms, i.e. α-glucose and
β-glucose, called anomers. α-D(+)-Glucose is obtained when a concentrated aqueous or
alcoholic solution is crystallised at 303 K. It has a melting point of 419 K and has a
specific rotation of +111° in a freshly prepared aqueous solution.
However, when glucose is crystallised from water above 371 K, β-D(+)-glucose is
obtained. It has a melting point of 423 K and has a specific rotation of +19.2° in a
freshly prepared aqueous solution. This behaviour could not be explained by the open
chain structure of glucose.
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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.
Fill in the blanks by choosing the appropriate word/words from those given in the brackets:
(iodoform, acetaldehyde, positive, greater, acidic, acetone, disaccharide, negative, increases, glucose, decreases, chloroform, polysaccharide, lactose, lesser, basic, cationic hydrolysis, anionic hydrolysis)
Sucrose is a _________ and yields upon hydrolysis, a mixture of ________ and fructose.
Write the reactions involved when D-glucose is treated with the following reagent:
(CH3CO)2O
What is the most abundant organic compound on earth?
Oxime is formed by treating glucose with ____________.
Glucose does not give Schiff’s test because of the formation of cyclic ____________.
Which of the following statements is incorrect regarding glucose?
When glucose reacts with bromine water, the main product is ____________.
Which of the following properties of glucose cannot be explained by its open chain structure?
(i) Glucose does not form hydrogen sulphite with NaHSO3.
(ii) On oxidation with HNO3 glucose gives saccharic acid.
(iii) Glucose is found to exist in two different crystalline forms which are named as α and β.
Reduction of glucose by HI suggest that ____________.
Which is the least stable form of glucose?
The two forms of D-glucopyranose obtained from the solution of D-glucose are called ____________.
Which one is correct?
Which one of the following reactions is not explained by the open chain Structure of glucose?
How will you distinguish 1° and 2° hydroxyl groups present in glucose? Explain with reactions.
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?
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
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 ______.
Give the reaction of glucose with hydrogen cyanide. Presence of which group is confirmed by this reaction?
