Biomolecules and Chemistry in Everyday Life - Result Question 26
####27. For ‘invert sugar’, the correct statement(s) is (are) (Given: specific rotations of $(+)$ - sucrose, $(+)$ - maltose, $L-(-)$-glucose and $L-(+)$-fructose in aqueous solution are $+66^{\circ},+140^{\circ},-52^{\circ}$ and $92^{\circ}$, respectively)
(2016 Adv.)
(a) Invert sugar is prepared by acid catalysed hydrolysis of maltose
(b) Invert sugar is an equimolar mixture of D-(+) -glucose and $D$-(-)- fructose
(c) Specific rotation of invert sugar is $-20^{\circ}$
(d) On reaction with $Br _2$ water, invert sugar forms saccharic acid as one of the products
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Answer:
Correct Answer: 27. $A \rightarrow p, s ; B \rightarrow q, r ; C \rightarrow p, r ; D \rightarrow s$
Solution:
- If there is inversion of specific rotation from (+) to (-), then invert sugar is formed.
(a) $C _{12} H _{22} O _{11}+H _2 O \longrightarrow$ Glucose
(b) $C _{12} H _{22} O _{11}+H _2 O \longrightarrow$ Glucose + Fructose
There is formation of invert sugar. Thus, correct.
(c) Specific rotation of invert sugar is $-20^{\circ}$ per mole. Thus, correct.
(d) $Br _2$ water is a weak oxidising agent. It oxidises $-CHO$ to $-COOH$ - $CH _2 OH$ group is not affected.
Saccharic acid
Gluconic acid (one of the products)
$HNO _3$ (a strong oxidising agent) oxidises invert sugar to saccharic acid. Thus, incorrect.
