stereochem

Question 1

stereoisomers

Answer 1

molecules with the same connectivity of atoms but different spatial arrangements

Question 2

types of stereoisomers

Answer 2

1. Enantiomers: Non-superimposable mirror images; created by inverting all stereocenters. Always chiral.
2. Diastereomers: Stereoisomers that are not mirror images; includes any stereoisomer that isn’t an enantiomer.

Question 3

non superimposable mirror images

Answer 3

Mirror-image molecules that cannot be aligned perfectly; enantiomers fall into this category.

Question 4

elements of stereochemistry

Answer 4

1. Stereocenters: Usually sp³ hybridized carbons with four different groups attached.
2. Alkenes: C=C double bonds in oppositely substituted even-sized rings; restricted rotation leads to cis/trans (E/Z) isomerism.

Question 5

stereocenter

Answer 5

Typically an sp³ hybridized atom (often carbon) attached to four different groups.

Question 6

what is the purpose of a stereocenter

Answer 6

They are the main contributors to chirality; inverting a stereocenter changes its spatial arrangement.

Question 7

how do double bonds affect rotation in molecules?

Answer 7

C=C double bonds do not rotate freely like single bonds, leading to geometric isomers (E/Z or cis/trans).

Question 8

what are oppositely substituted even sized rings

Answer 8

Rings with double bonds and substituents opposite to each other; important for identifying cis/trans isomerism.

Question 9

how do you calculate the number of stereoisomers?

Answer 9

Use the formula 2^n, where 𝑛
n is the number of stereocenters or stereogenic elements (e.g., chiral centers or double bonds). DON’T FORGET TO SUBTRACT NUMBER BY 1, BECAUSE ORIGINAL MOLECULES DOESN’T COUNT

Question 10

What is chirality

Answer 10

The property of a molecule lacking a mirror plane (asymmetrical), making it non-superimposable on its mirror image.

Question 11

what are optically active molcules

Answer 11

chiral molecules that rotate plane-polarized light.

Question 12

what are enantiomers

Answer 12

Always chiral molecules that have a chiral counterpart that is a mirror image.

Question 13

what are meso compounds

Answer 13

Compounds that are achiral despite having stereocenters due to internal symmetry (mirror plane).

Question 14

what are the rules for assigning R/S configuration using CIP rules?

Answer 14

1. Prioritize Substituents: Based on atomic number; higher atomic number = higher priority.
2. Multiple Bonds: Count as if bonded to additional atoms.
3. Identical Atoms: Move one bond away to find the first point of difference.
   NBE: Receives the lowest priority (0).

Question 15

how do you determine the R/S configuration?

Answer 15

1. Orient the molecule so that the lowest-priority group points backward.
2. Trace from the highest priority (1) to third priority (3):
   Clockwise (CW) = R
   Counterclockwise (CCW) = S

Question 16

what if the lowest prioirty isn’t in the back?

Answer 16

Newman Projections: View the molecule from different perspectives.
Break and Switch Method: Swap the lowest-priority substituent with one in the back, determine R or S, then switch the label.
Double Displacement: If a simple switch isn’t feasible, perform two swaps.

Question 17

what are structural isomers?

Answer 17

Isomers with different connectivity but the same molecular formula.

Question 18

what are stereoisomers

Answer 18

Isomers with the same molecular formula and connectivity, differing in spatial orientation (R/S, E/Z).

Question 19

what are rigid structures in relation to double bonds?

Answer 19

Structures with rigid double bonds or rings that restrict rotation.

Question 20

how do even sized rings exhibit stereoisomerism?

Answer 20

Even-sized rings can show cis/trans isomerism, especially with opposite substitutions.

Question 21

what are the E/Z rules for alkenes?

Answer 21

E (entgegen): High-priority groups on opposite sides of the double bond.
Z (zusammen): High-priority groups on the same side.

Question 22

how do you apply priority assignment for E/Z?

Answer 22

Use the same priority rules as R/S; determine if highest priority groups are on the same (Z) or opposite (E) sides.

Question 23

what are the special cases for rings with hydrogen substituents?

Answer 23

Cis/trans naming applies when comparing H atoms across double bonds in rigid rings.

Question 24

what is unique about meso compounds

Answer 24

Meso compounds could have multiple stereocenters but are achiral due to an internal mirror plane; they don’t have enantiomers

Question 25

how do oppositely substituted rings behave?

Answer 25

They show stereoisomerism based on substituent position but lack true stereocenters due to symmetry.

Question 26

what is a chiral center

Answer 26

A carbon with four distinct groups; it is the main cause of chirality.

Question 27

what are useful methods for visualizing configurations?

Answer 27

Newman Projections: Visualize group arrangements on stereocenters.
Break and Switch: For quick orientation swaps, especially for identifying enantiomers.
Double Displacement Method: Use when the lowest-priority group is hard to position in the back.

Question 28

do double bonds in small rings count as elements of stereochemistry?

Answer 28

NO!

Question 29

is formation of a carbocation high or low energy?

Answer 29

forming a CC is an unstable process, so highest energy

Question 30

delocalization contributes to

Answer 30

resonance stability, which makes for an easier and faster reaction

Question 31

what do you need for something to be optically active?

Answer 31

stereocenters!

Question 32

how to calculate the number of diastereomers

Answer 32

2^n - 2

Question 33

units of unsaturation formula

Answer 33

(2n + 2) - # Hs - # halogens + # Ns

Question 34

units of unsaturation combos

Answer 34

1 double bond = 1 UU
1 triple bond = 2 UU
1 ring = 1 UU