Question

Which one of the following is laevorotatory?
A.glucose
B.fructose
C.sucrose
D.all the above

Answer 1

Hint: Those which rotate the plane polarised light toward counter clockwise direction is known as laevorotatory which is denoted​ by l or -. Fructose is laevorotatory. It rotates the plane of polarized light in an anticlockwise direction.

Complete answer:
Some chiral compounds which don't have plane of symmetry have some property to rotate plane polarised light in either clockwise or counter clockwise direction.
Those compounds which rotate plane polarised light toward clockwise direction are known as dextrorotatory which is denoted by d or + and those which rotate the plane polarised light toward counter clockwise direction is known as laevorotatory which is denoted​ by l or -.
Fructose has three chiral centres, that is why it is optically active. Its specific rotation is -92.4. The negative sign shows that light rotates toward counter clockwise direction.
When the fructose solution is placed in a polariser it rotates the plane polarized light in an anti-clockwise direction which is towards the left side. So, it is a laevorotatory nature compound. Honey contains monosaccharides sugar fructose.
This specific rotation is an experimental phenomenon; we can’t predict specific rotation after seeing the structure.

So, the correct answer is option B.
Note: Fructose (fruit sugar) is a ketohexose which is a six-carbon ketonic sugar, and it occurs in sweet fruits and honey. Glucose and fructose have the same molecular formula, i.e. ${C_6}{H_{12}}{O_6}$, but they have different structures. Pure, dry fructose is very sweet in taste, white in colour, odourless and crystalline solid. Fructose is one of the sweetest of all sugars and is combined with glucose to make sucrose, or common table sugar. Fructose’s name is also levulose because of its levorotatory property of rotating plane polarized light to the left.