Review 2 - Chapter 5 Key topics: Chirality Stereochemical...

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Key topics: Chirality Stereochemical assignment Stereoisomers Prochirality Chirality at heteroatoms Chapter 5
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Non-superimposable mirror images Equivalent definition: lack of planar symmetry Chirality
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Chiral molecules rotate plane-polarized light Such molecules are said to be optically active The extent of rotation is referred to as optical rotation Chirality
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Normalized optical rotation is called specific rotation Adjusts for path length and concentration Chirality
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Atoms are chiral if they attached to 4 non-identical groups Assign R or S by Cahn–Ingold–Prelog rules 1. Prioritize by atomic number a. If isotopes, prioritize by atomic mass b. Electron lone pair is lower priority than hydrogen 2. If same atom, look one atom away at a time 3. Treat multiple-bonded atoms as equivalent number of single-bonded atoms 4. Place lowest priority group in back 1. Groups clockwise: assign R configuration 2. Groups counterclockwise: assign S configuration Stereochemical Assignment
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Stereochemical Assignment
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Stereochemical Assignment
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Priority 4 in front, switch direction Switch any two groups, switch configuration Stereochemical Assignment
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Enantiomers: non-superimposable mirror images Rotate plane-polarized light in opposite directions Otherwise identical properties in non-chiral environment Other ways to recognize: All wedges and dashes switched All configurations switched Generally inseparable unless turned into diastereomers Often through salt formation with chiral partners Can be distinguished by a biological system Stereoisomers
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This note was uploaded on 12/09/2011 for the course CHEM 331 taught by Professor Chen during the Spring '11 term at Iowa Central Community College.

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Review 2 - Chapter 5 Key topics: Chirality Stereochemical...

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