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Invert sugar is an equimolar mixture ofA. D- frustose and L- fructoseB. D- glucose and L- glucoseC. D- glucose and L- fructoseD. D- glucose and D- fructose

Answer» Correct Answer - D
Aqueous solution of cane sugare (sucrose) is dextrorotatory, `(alpha)_(D) = + 66.5^(@)`. On hydrolysis with dilute acid of enzyme invertase, cane sugar gives equimolar mixture of `D - (+)-` glucose and `D - (-) -` fructose.
`underset([alpha]_(D)=+66.5^(@))underset("Sucrose")(C_(12)H_(22)O_(11)+H_(2)O) overset(HCl)rarr underset([alpha]_(D)=+52.5^(@))underset("D-glucose")(C_(6)H_(12)O_(6))+underset([alpha]_(D)=-92.4^(@))underset("D-fructose")(C_(6)H_(12)O_(6))`
Sucrose is dextrorotatory but hydrolysis gives dextrorotatory glucose and laevorotatory fructose.
Since the laevorotation of fructose `(-92.4^(@))` is more than dextrorotation of glucose `(+ 52.5^(@))`, the mixture is laevorotatory. Thus, hydrolysis of sucrose bring about a change in the sign of rotation, from dextro `(+)` to laevo `(-)` and such a change is known in inversion and the mixture is known as invert sugar.


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