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(a) Despite having an aldehydic group, g...

(a) Despite having an aldehydic group, glucose does not give 2, 4-DNP test. What does it indicate ?
(b) Draw Haworth structure of `alpha-D(+)` glucopyranose
(c ) What is the significance of D and (+) here ?

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### Step-by-Step Solution #### (a) Why does glucose not give the 2,4-DNP test despite having an aldehydic group? 1. **Understanding the 2,4-DNP Test**: The 2,4-dinitrophenylhydrazine (2,4-DNP) test is used to detect the presence of aldehydes and ketones. A positive test results in the formation of a yellow-orange precipitate, indicating the presence of these functional groups. 2. **Structure of Glucose**: Glucose exists primarily in a cyclic form (pyranose) rather than in its open-chain form. In the cyclic structure, the aldehydic group (which is located at the first carbon in the open-chain form) reacts with the hydroxyl group of the fifth carbon to form a hemiacetal. ...
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Despite having an aldehyde group : (a) Glucose does not give 2,4-DNP test. What does this indicate ? (b) Draw the Haworth structure of alpha -D-(+)-glucopyranose. (c) What is the significance of D and (+) here?

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Knowledge Check

  • Assertion: Glucose does not gives 2,4-DNP test. Reason: Glucose exists in cyclic hemiacetal form

    A
    If both assertion and reason are true and reason is the correct explanation of assertion.
    B
    If both assertion and reson are true but reason is not the correct explanation of assertion.
    C
    if assertion is true but reason is false.
    D
    If both assertion and reason are false.

  • What does 'D' and (+) signifies in D - (+) glucose?

    A
    D represents conformation and (+) represents the laevorotatory nature of molecule.
    B
    D represents conformation and (+) represents the dextrorotatory nature of molecule.
    C
    D represents configuration and (+) represents the laevorotatory nature of molecule.
    D
    D represents configuration and (+) represents the dextrorotatory nature of molecule.

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    (i) Which of the following biomolecules is insoluble in water ? Justify. Insulin, Haemoglobin, Keratin. (ii) Draw the Haworth structure for alpha -D-Glucopyranose. (iii) Write chemical reaction to show that glucose contains aldehyde as carbonyl group.

    (i) Which of the following biomolecule is insoluble in water ? Justify. Insulin, Haemoglobin, Keratin. (ii) Draw the Haworth structure for alpha -D-Glucopyranose. (iii) Write chemical reaction to show that glucose contains aldehyde as carbonyl group.

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