Which sugar is called invert sugar? Why is it called so?

Explanation

Equimolar mixture of `D-(+)-`glucose and `D-(-)-`fructose (which are obtained by hydrolysis of sucrose) is called invert sugar. Sucrose is dextrorotatory with a specific rotation of `+66.5^(@)`. On hydrolysis it produces a `1 : 1` mixture of glucose `(+52.5^(@))` and fructose `(-92^(@))`and this mixture has a specific rotation of `-19.75^(@)` i.e., the mixture is laevorotatory. Because of such change in the sign of optical rotation, the hydrolysis of sucrose is called inversion of sucrose and the mixture of glucose and fructose obtained by hydrolysis is called invert sugar.