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Topic H

Types of Isomers: Constitutional Isomers, Stereoisomers, Enantiomers, and Diastereomers

1.The Types Of Relationships Between Molecules

RULES:
a given pair of molecules can be isomers or non-isomer
isomers: constitutional isomers or stereoisomers
stereoisomers: enantiomers or diastereomers

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2.How To Distinguish A Pair Of Non-Isomers vs. A Pair Of Isomers

isomers: two or more molecules that share the same molecular formula
some molecular formulas have no isomers such as CH4 or C3H8
despite sharing the same molecular formula, isomers have very different physcial properties, such as boiling point, melting point, and chemical reactivity

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3.Types Of Isomers: Constitutional Isomers Have Different Connectivites

consitutional isomers: same molecular formula but different connectivities
the same parts but arranged in different ways

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4.Types Of Isomers: Stereoisomers Have The Same Connectivity But A Different Arrangement Of Their Atoms In Space

stereoisomers: same connectivity, but different arrangements in space

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since free rotation about the double bond is not possible, these are two completely distinct molecules. They have the same connectivity but differ in arrangement of their groups in space

5.Stereogenic “Elements” In Stereoisomers

A quick way to tell if two molecules are stereoisomers is if they have the same core IUPAC name but differ in cis/trans, E/Z, or R/S designations

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6.Types Of Stereoisomers: Enantiomers vs. Non-Enantiomers (a.k.a. Diastereomers)

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7.What Does “Non-Superimposable Mirror Image” Even Mean??

superimposed molecules: through rotation of bonds or through the rotation of the molecule itself you can get the same molecule

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8.Property Brothers Season 13, Episode 13: “Lord Voldemort And The Property Of Chirality”

Asymmetry/chirality: the left half of a molecule does not match the right half of the molecule

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9.Enantiomers Have Identical Physical Properties Except for Optical Rotation

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10. “The Third Property Brother”: meso-Tartaric Acid

meso: A superimposable mirror image and therefore identical molecules

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11.Only Chiral Molecules Can Have Enantiomers

only chrial molecules can have enantiomers

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A molecule with an internal mirror plane- plane of symmetry- is achiral and will not have an enantiomer

12.Diastereomers Are Stereoisomers That Are Not Enantiomers 13.Diastereomers Have Different Physical Properties 14. A Quick Way To Tell If Two Stereoisomers Are Diastereomers

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