Draw the mirror images of glucose and fructose. Are glucose and fructose chiral? Do you expect them to be optically active?

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Draw the Fischer projection of D-glucose, which is an aldohexose with the formula C_6H_{12}O_6.

Draw the mirror image of D-glucose by reflecting each chiral center across a vertical axis to obtain L-glucose.

Draw the Fischer projection of D-fructose, which is a ketohexose with the formula C_6H_{12}O_6.

Draw the mirror image of D-fructose by reflecting each chiral center across a vertical axis to obtain L-fructose.

Discuss the chirality: Glucose has multiple chiral centers, making it chiral and optically active. Fructose also has chiral centers, making it chiral and optically active.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Chirality

Chirality refers to the geometric property of a molecule that makes it non-superimposable on its mirror image. A chiral molecule typically has at least one carbon atom bonded to four different substituents, resulting in two distinct forms known as enantiomers. Understanding chirality is crucial for determining the optical activity of compounds, as chiral molecules can rotate plane-polarized light.

Optical Activity

Optical activity is the ability of a chiral substance to rotate the plane of polarized light. This property arises from the asymmetry of chiral molecules, which can exist in two enantiomeric forms that rotate light in opposite directions. The degree of rotation is measured using a polarimeter and is an important characteristic in distinguishing between different enantiomers in organic compounds.

Structural Isomers

Structural isomers are compounds that have the same molecular formula but differ in the arrangement of atoms. Glucose and fructose are structural isomers, specifically aldose and ketose sugars, respectively. This difference in structure affects their physical and chemical properties, including their chirality and optical activity, making it essential to analyze their configurations when discussing their mirror images.

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Related Practice

Textbook Question

Which of the following compounds are chiral? Draw each compound in its most symmetric conformation, star (*) any asymmetric carbon atoms, and draw any mirror planes. Label any meso compounds. You may use Fischer projections if you prefer.

(e) (R,R)-2,3-dibromobutane

(f)

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Textbook Question

Which of the following pairs of compounds could be separated by recrystallization or distillation?

a. meso-tartaric acid and (±)-tartaric acid (HOOC—CHOH—CHOH—COOH)

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Textbook Question

Which configuration (R or S) does the bottom asymmetric carbon have for the D series of sugars? Which configuration for the L series?

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Textbook Question

Which of the following pairs of compounds could be separated by recrystallization or distillation?