The change in optical rotation with time is called:

Question

Question

This question was previously asked in

DSSSB PGT Chemistry (Female) Official Paper (Held On: 06 Jul, 2018 Shift 1)

Answer 1

CONCEPT:

Muta rotation

Muta rotation refers to the change in the optical rotation of a solution over time, which occurs due to the equilibrium establishment between different anomeric forms of a carbohydrate, particularly monosaccharides.
When a sugar is dissolved in water, it can exist in different forms (e.g., alpha and beta anomers). These forms interconvert until an equilibrium is reached, resulting in the optical rotation changing with time.
This phenomenon is commonly observed in reducing sugars like glucose.

EXPLANATION:
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In the case of carbohydrates, such as glucose:
- When glucose is dissolved in water, it exists in two cyclic forms: alpha-D-glucose and beta-D-glucose.
- The alpha form has one optical rotation value, while the beta form has another.
- These forms interconvert through the open-chain structure, leading to a change in optical rotation until equilibrium is established.
This change in optical rotation over time is termed "muta rotation."
It is a characteristic property of reducing sugars and is influenced by factors such as temperature and pH.

Therefore, the change in optical rotation with time is called Muta rotation.