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)

specific rotation of ‘invert sugar’ is $-{20}^{\circ }$

$C_{12}{H}_{22}{O}_{11}+H_{2}O\stackrel{H^{+}}{\to }\underset{+{52}^{\circ }}{\underset{D-(+)-glucose}{C_6{H}_{12}{O}_6}}+\underset{-{92}^{\circ }}{\underset{D-(-)-fructose}{C_6{H}_{12}{O}_6}}{\alpha }_{\text{invert sugar}}=\frac{{52}^{\circ }-{92}^{\circ }}{2}=-{20}^{\circ }$ (average is taken as both monomers are one mole each)
Invert sugar is a mixture of glucose and fructose. Glucose on reaction with bromine water gives gluconic acid where the aldehydic group gets oxidised to carboxylic group. Fructose is unaffected by the addition of bromine water.