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Ch.20 Carbohydrates
McMurry - Fundamentals of General, Organic, and Biological Chemistry 8th Edition
McMurry8th EditionFundamentals of General, Organic, and Biological ChemistryISBN: 9780134015187Non è quello che usi tu?Cambia libro di testo
Capitolo 20, Problema 42b

Sucrose and D-glucose rotate plane-polarized light to the right; D-fructose rotates light to the left. When sucrose is hydrolyzed, the glucose–fructose mixture rotates light to the left.
b. Why do you think the mixture is called “invert sugar”?

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1
Understand the concept of optical rotation: Optical rotation refers to the ability of a compound to rotate plane-polarized light. Compounds that rotate light to the right are called dextrorotatory (denoted as '+'), while those that rotate light to the left are called levorotatory (denoted as '-').
Recognize the behavior of sucrose: Sucrose is dextrorotatory, meaning it rotates plane-polarized light to the right. This is due to the combined optical activities of its glucose and fructose components in the intact molecule.
Analyze the hydrolysis of sucrose: During hydrolysis, sucrose breaks down into its monosaccharide components, d-glucose and d-fructose. While d-glucose is dextrorotatory, d-fructose is strongly levorotatory. The levorotatory effect of d-fructose dominates in the mixture.
Explain the term 'invert sugar': After hydrolysis, the overall optical rotation of the mixture changes direction from right (dextrorotatory) to left (levorotatory). This inversion of the direction of rotation is why the resulting mixture is called 'invert sugar.'
Summarize the significance: The term 'invert sugar' reflects the change in optical rotation caused by the hydrolysis of sucrose into its monosaccharide components, which alters the net optical activity of the solution.

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Optical Activity

Optical activity refers to the ability of certain substances to rotate plane-polarized light. This property is due to the chiral nature of the molecules, which can exist in two enantiomeric forms that interact differently with light. For example, d-glucose and sucrose rotate light to the right (dextrorotatory), while d-fructose rotates it to the left (levorotatory).
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Hydrolysis of Sucrose

Hydrolysis of sucrose involves breaking down the disaccharide into its constituent monosaccharides, glucose and fructose, typically through the action of an enzyme or acid. This reaction alters the optical activity of the solution, as the resulting mixture of glucose and fructose exhibits a net rotation to the left, contrasting with the right rotation of sucrose.
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Invert Sugar

Invert sugar is the term used for the mixture of glucose and fructose produced when sucrose is hydrolyzed. The name 'invert' comes from the fact that the hydrolysis process changes the direction of optical rotation from right to left, indicating a change in the sugar's properties. Invert sugar is sweeter than sucrose and is commonly used in food products for its desirable taste and moisture-retaining qualities.
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