Question

Invert sugar is a mixture of

• A. glucose and fructose
• B. glucose and lactose
• C. glucose and galactose
• D. only glucose

Answer 1

Answer: (A)

$\underset{\begin{array}{c}sucorse\\ \\ {[\alpha ]}_D=+{66.5}^o\end{array}}{C_{12}{H}_{22}{O}_{11}}+H_{2}O\stackrel{HCl}{\to }\underset{\begin{array}{c}D(+)glu\cos e\\ \\ {[\alpha ]}_D=+{52.5}^o\end{array}}{C_6{H}_{12}{O}_6}$ $+\underset{\begin{array}{c}D(-)fructose\\ {[\alpha ]}_D=-{92.4}^o\end{array}}{C_6{H}_{12}{O}_6}$ Sucrose is dextrorotatory and the resulting solution is laevorotatory with specific rotation of $-39.9{}^{\circ }$ because fructose has a greater specific rotation. Since, there is a change in sign from dextrorotatory to laevorotatory, the reaction is called inversion reaction and thus, sucrose (obtained from glucose and fructose) is called invert sugar.