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Question
What is the correct name of the following compound?
What is the correct name of the following compound?
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Solution
The correct option is C L-(+)-fructose
Steps to Find Out D & L Configuration
1. Write the molecule in such a way that most oxidised carbon (-CHO) is at top.
2. Check lowest chiral carbon.
3. Observe the position of -OH attached to that carbon.
(a) if -OH on the right side, assigned as 'D' configuration.
(b) if -OH on the left side, assigned as 'L' configuration.
Optical Behaviour of Glucose
(+) or (d) represents → Dextrorotatory
(-) or (l) represents → Laevorotatory
NOTE: D and L are relative configuration and have no relation with d/(+) and l/(-).
Since the -OH group on the lowest chiral carbon adjacent to the last CH2OH group is on the left-handside, it is of L configuration. Also, L-fructose is dextrorotatory compound, hence the (+) sign.
Thus, the given fructose is correctly named as L-(+)-fructose. Hence (c) is the correct option.
Steps to Find Out D & L Configuration
1. Write the molecule in such a way that most oxidised carbon (-CHO) is at top.
2. Check lowest chiral carbon.
3. Observe the position of -OH attached to that carbon.
(a) if -OH on the right side, assigned as 'D' configuration.
(b) if -OH on the left side, assigned as 'L' configuration.
Optical Behaviour of Glucose
(+) or (d) represents → Dextrorotatory
(-) or (l) represents → Laevorotatory
NOTE: D and L are relative configuration and have no relation with d/(+) and l/(-).
Since the -OH group on the lowest chiral carbon adjacent to the last CH2OH group is on the left-handside, it is of L configuration. Also, L-fructose is dextrorotatory compound, hence the (+) sign.
Thus, the given fructose is correctly named as L-(+)-fructose. Hence (c) is the correct option.
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