Question

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)

• A. 'invert sugar' is prepared by acid catalyzed 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 $B{r}_2$ water, 'invert sugar' forms saccharic acid as one of the products

Answer 1

Answer: (B), (C)

(A) Wrong invert sugar is formed by sucrose not by maltose
(B) Equimolar mixture of $D(+)$ glucose and $D(-)$-fructose
(C) specific rotation of invert sugar is $-20^{\circ }$

Invert sugar is hydrolysed sucrose, initially sucrose is dextrorotatory but finally solution is laevorotatory.
(ii) Specific rotation is average of both optical rotation of glucose and fructose
Specific rotation $=\frac{{\theta }_{\text{Glucase }}+{\theta }_{\text{Fnstose }}}{2}$
$=\frac{+52-92}{2}=-20^{\circ }$
(D) Glucose $\stackrel{\mathrm{Br}{}_2/\mathrm{H}{}_2\mathrm{O}}{\to }$ Gluconic acid (NOT saccharic acid) Wrong