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Questions and Answers
What is the fundamental difference between stereoisomers?
What is the fundamental difference between stereoisomers?
- They have different molecular weights.
- They have different empirical formulas.
- They have different arrangements of atoms in space. (correct)
- They have different structural formulas.
Which statement accurately describes optical isomerism?
Which statement accurately describes optical isomerism?
- Isomers with the same molecular and structural formulas, differing in their interaction with plane-polarized light. (correct)
- Isomers that rotate ordinary light in opposite directions.
- Isomers with different molecular formulas but similar structural arrangements.
- Isomers with different physical properties but identical chemical properties.
What is the principal function of a Nicol prism in the context of optical activity?
What is the principal function of a Nicol prism in the context of optical activity?
- To convert ordinary light into plane-polarized light. (correct)
- To split ordinary light into its component colors.
- To measure the refractive index of a solution.
- To amplify the intensity of ordinary light.
In a polarimeter, what observation indicates that a compound is optically inactive?
In a polarimeter, what observation indicates that a compound is optically inactive?
A compound rotates plane-polarized light to the left. How is this optical activity characterized?
A compound rotates plane-polarized light to the left. How is this optical activity characterized?
Which of the following correctly pairs the direction of rotation with its corresponding term?
Which of the following correctly pairs the direction of rotation with its corresponding term?
Two stereoisomers have nearly identical physical and chemical properties. How can you distinguish between them?
Two stereoisomers have nearly identical physical and chemical properties. How can you distinguish between them?
A researcher observes that a solution of a particular compound does not alter the direction of plane-polarized light. What conclusion can be drawn?
A researcher observes that a solution of a particular compound does not alter the direction of plane-polarized light. What conclusion can be drawn?
If a compound is found to be dextrorotatory, what specific effect does it have on plane-polarized light?
If a compound is found to be dextrorotatory, what specific effect does it have on plane-polarized light?
What is the relationship between optical isomerism and stereoisomerism?
What is the relationship between optical isomerism and stereoisomerism?
Flashcards
Stereoisomers
Stereoisomers
Isomers with the same molecular and structural formula, differing in spatial arrangement.
Optical Isomerism
Optical Isomerism
A type of stereoisomerism where isomers have the same molecular and structural formulas but differ in their interaction with plane-polarized light.
Plane-Polarized Light
Plane-Polarized Light
Light in which the waves oscillate in only one direction/plane.
Polarimeter
Polarimeter
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Optically Active Compound
Optically Active Compound
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Dextrorotatory
Dextrorotatory
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Levorotatory
Levorotatory
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Optically Inactive Compound
Optically Inactive Compound
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Study Notes
Introduction to Stereoisomerism and Optical Activity
- Lecture focuses on stereoisomerism, especially optical activity, crucial in pharmaceutical organic chemistry.
- Stereoisomerism involves compounds sharing a molecular formula but differing in their atoms' spatial arrangements.
- Recommends watching lectures in sequence for clear understanding.
- The lecture will cover geometric and optical isomerism within the current unit.
Understanding Stereoisomers
- Stereoisomers share the same molecular and structural formula.
- Stereoisomers differ in their arrangement of atoms in space, such as group orientations on a carbon atom.
- Rotation around single bonds yields different spatial arrangements, altering the compound's appearance.
Optical Isomerism: Definition and Key Differences
- Optical isomerism, a stereoisomerism subset, features isomers that have identical molecular and structural formulas.
- Physical and chemical properties are generally the same for optical isomers, with exceptions for optically active compounds.
- Their behavior towards light, especially plane-polarized light, is the key differentiating factor.
Ordinary Light vs. Plane-Polarized Light
- Ordinary light's waves oscillate in every direction.
- A polarizer, like a Nicol prism made of caco3, transforms ordinary light into plane-polarized light by aligning light waves in one plane.
- The Nicol prism concentrates and emits light as a thin layer of plane-polarized light.
Polarimeter and Optical Activity Detection
- A polarimeter assesses a substance's optical activity.
- A compound solution is placed inside the polarimeter.
- Plane-polarized light is directed through the solution.
- The light exiting the solution will be unaffected (straight), rotated clockwise, or rotated counterclockwise.
- These outcomes determine a compound's optical activity.
Interpretation of Results: Optically Active vs. Inactive Compounds
- If light passes through unchanged, the compound is optically inactive, meaning it doesn't rotate plane-polarized light.
- Light rotation indicates an optically active compound.
- Clockwise rotation is "dextrorotatory," denoted by a plus (+) sign.
- Counterclockwise rotation is "levorotatory," denoted by a minus (-) sign.
- Notes on this will be provided.
Summary of Optical Activity
- If a compound rotates plane-polarized light, it is optically active.
- Dextrorotatory describes rightward (clockwise) rotation.
- Levorotatory describes leftward (counterclockwise) rotation.
- No rotation suggests an optically inactive compound.
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