Vocab Review - (CH. 5)

Stereoisomer

They have the same connections, but their orientation is DIFFERENT

⭐all atoms are hooked on the SAME way (alkenes have cis& trans sterochemistry)

Enantiomer

Perfect mirror image of the compound

Diastereomer

NOT perfect image of the compond

cis

on same side of ring

⭐double bonds HAVE cis/trans stereochemistry (bottom example)

trans

on the opposite side of the ring

⭐double bonds HAVE cis/trans stereochemistry (bottom example)

⭐know the difference between:

1) identical compounds

2) constitutional isomers

3) stereoisomers (enantiomers & diastereomers)

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Superimposed

placed or laid over something else, typically so that both things are still evident:

⭐Chiral

a molecule that is NOT superimposable on its mirror image (like your hands!)

⭐Achiral

a molecule that IS superimposable on its mirror image (has NO chiral centers)

⭐PRACTICE:

Chiral VS. Achiral

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Chiral Center (aka “Stereocenter”)

An atom that can create “chirality” in the molecule

⭐4 diff. groups = chiral center

⭐when you switch 2 groups, you will NEVER be able to line them up

How to find a Chiral Center (Stereocenter)?

It has 4 different substituents attached

⭐when you switch two groups, it becomes R (clockwise)

⭐when you switch two groups, it becomes S (counter-clockwise)

⭐Tips for Drawing “Enantiomers”⭐

1) Keep everything drawn the same, but FLIP what is on the dash/wedge on EACH stereocenter

2) Draw the mirror image (more difficult)

3) Use model kits to help you visualize

⭐hydrogen is USUALLY lowest priority (4th substituent; not always)

⭐hydrogen has to be in the back to figure out S or R

⭐Two common occurrences⭐

• cis/trans stereoisomers ARE diasteromers

• A molecule w/ at least 2 stereocenters can have diastereomers (in addition to its enantiomers)

Meso Compound

A compound w/ chiral centers, BUT its mirror image is superimposable (achiral)

⭐Meso compounds have NO enantiomer (it’s mirror image is the SAME compound)

How do you find “Meso Compound”

Usually they have an INTERNAL plane of symmetry