Organic Chemistry Exam 2

chiral

nonsuperimposable mirror images

achiral

superimposable mirror images

chiral molecule

molecule with a non-superimposable mirror image (has a chiral center)

configurational isomers

molecules that are the same in 2D, but have different 3D arrangements in space

stereocenter (chiral center)

tetrahedral arom with four different groups attached

Steps to assigning stereochemistry

1. Rank groups by atomic number (if first group is the same, continue down the chain

2. Rotate the molecule so that the lowest priority group points back

3. Draw an arrow from the first to third priority molecule

4. Assign R and S

enantiomers

non-superimposable mirror images (occurs when all stereoisomers switch configuration)

diastereomers

configurational isomers that are not enantiomers (some stereoisomers switch configuration)

How many stereoisomers do molecules have?

2^n (where n is the number of stereocenters)

In optical activity, how to pure samples of enantiomers rotate light?

Equally, in opposite directions

Meso compounds

Molecules that contain chiral centers but are achiral (contain a plane of symmetry)

Nucleophile

Electron donor (Lewis base)

Electrophile

Electron acceptor (Lewis acid)

concerted pathway

a reaction pathway where multiple steps occur at the same time (Type 2)

transition states

short-lived high-energy states that form as bonds break

Why do Sn2 reactions contain a “backside attack”?

• Due to steric bulk, there is often stuff in the way on the front side

• The position of the C-LG antibonding orbital (LUMO)

• The leaving group is electron-rich

In Sn2 happens to the stereochemistry of the molecule at the substituted carbon?

It inverts (flips like an umbrella)

step-wise

parts of a reaction occur one at a time