Chapter 5 Sterioisomerism 

Constitutional Isomers: Same molecular formula but different constitution order of connectivity of atoms

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Stereoisomers: Same molecular formula and constitution but different spatial arrangements of atoms

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Cis (same) Trans (different)

A cis stereoisomer has groups all on the same side

A trans stereoisomer has groups all on different sides

Chemists use cis-trans terminology to describe disubstituted (has two substituent atoms/groups) alkenes, even when the two substituents (connected to the π bond) are different from each other

Chirality and Introduction to Stereoisomerism

Superimposable- mirror image is identical to the actual object.

Nonsuperimposable- the object and its mirror image are now different

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Diasterisomers are stereoisomers that are not mirror images

The most common source of molecular chirality is the presence of a Carbon atom bearing 4 different groups

Is this a superimposing or nonsuperimposable image nonsuperimposable

Chirality describes nonsuperimposable images in their mirror’s reflection

achiral- can superimpose in their mirror image

A chiral center- is a tetraheadral carbon holding four different groups

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Locate the chiral center There is not chiral center here because it is symmetrical and the clockwise path and the counterclock wise path are intentical

Locate Chiral center There is a tetrahedreal with OH-C-C-H

Spot the Chiral centers

The Answer Located Chiral centers

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Testing for Chiralilty include:

Plane of symmetry (mirror plane) If plane can bisect molecule and it is same with its two halves it is achiral

Without internal plane is chiral

1. look for chiral centers

   1. if one it is chiral
   2. if more than one may or may not be chiral
   3. if none may or may not be chiral but probably not
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2. Look for mirror plane

   1. Then draw image to test if superimposable

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When a compound is nonsuperimposable, chiral mirror images of each other it is an Enantiomers

Compounds and its Enantiomers

Cahn Ingold Prelog

1. Order the four groups by atomic weight/number (#1 highest atomic weight)

2. Rotate so lowest atomic weight is pointing away

3. Point arc from highest priority to next highest priority

4. If turns counterclock wise <-- to c. center= @@R@@

   1. if turns counterclockwise -→ to c.center=^^S^^
   2. 

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