Stereochemistry - Configurational Flashcards
CHIRALITY
- etymology
- 4 factors for a molecule to be chiral
- Greek “cheir” (handedness)
- Has a chiral center
- No plane of symmetry
- Not superimposable with mirror image
- Has optical activity
Other term for chiral center
+ requirement to be considered a chiral center
stereogenic center
bonded to four DIFFERENT groups
Can only CARBON ATOMS be a chiral center?
No, basta bonded to 4 different groups, it can be a chiral center
usually lang, CARBON ang chiral center in organic molecules
WHAT do you call the opposite of chiral molecules?
+ what are 5 AUTOMATIC factors that make an object as such?
ACHIRAL
- sp
- sp2
- double bond
- triple bond
- lacks at least one of the factors to be a chiral molecule
OPTICAL ACTIVITY
- ability of a substance to ____ the ____ of _____-_____ light
- ____ property measured by a ____
- rotate
- plane
- plane-polarized
- light
- physical
- polarimeter
OPTICAL ROTATION
- 2 types
- rotation
- designated as?
- Dextrorotatory compounds
- clockwise
- (d*) or (+) - Levorotatory compounds
- counterclockwise
- (l*) or (-)
*italicized
3 representations of CHIRAL MOLECULES
+ composition
- Three-dimensional representation
* 2 ordinary straight lines (plane)
* 1 solid wedge (forward)
* 1 dashed line wedge (backward) - Wedge representation
* 2 horizontal solid wedge (forward)
* 2 vertical dashed line wedge (backward) - Fischer Projection Formula
* 4 ordinary straight lines in cross formation
* horizontal lines (forward)
* vertical lines (backward)
* does not show chiral center
CONFIGURATION vs ABSOLUTE CONFIGURATION
CON: arrangement of the 4 groups around a chiral CARBON
ABS CON: arrangement of the 4 groups around all chiral carbons based on a certain set of rules
ABSOLUTE CONFIGURATION (3 steps)
- assign priorities to four substituents based on CAHN-INGOLD-PRELOG sequence rules
- ranked 4th substituent must be at the back
- Determine rotation
R-rectus: clockwise
S-sinister: counterclockwise
Cahn-Ingold-Prelog Rules
steps (5)
- Look at the 4 atoms DIRECTLY ATTACHED to chiral center
- Assign priorities, with rank 1 given to the attached atom with the highest atomic number
- In case w/ isomers, prioritize the attached atom with the highest atomic mass
- In case w/ same atoms attached to chiral center, look at the second, third, fourth atoms outward
- If a multiple-bonded atom is attached, double or triple yung value ng attached atom
STEREOISOMERS
- formula to get max number of isomers
- how to write the different stereoisomers of a molecule
- 3 types/forms
2^n
wherein n = number of chiral centers
stereoisomers solely differ through orientation of a substituent
- Enantiomers
- Meso Form/Compound
- Diastereomers
ENANTIOMERS
- etymology
- stereoisomers related as ?
- 2 example pairs of enantiomers
- optical activity
+ chirality
- Greek “enantio” opposite
- non-superimposable mirror images
- d/l and R/S
- optically active
CHIRAL
MESO COMPOUNDS
- optical activity + reason
- has a ____ set of ____ substituents for ___ adjacent chiral centers
- _____ the number of expected stereoisomers
- so if 2 compounds are meso forms of each other, they are considered as how many stereoisomers?
+ chirality
- optically INACTIVE due to plane of symmetry
- common set of 4 substituents for 2 adjacent chiral centers
- decreases
- only 1 stereoisomers
ACHIRAL
WHAT are diastereomers
+ what type of isomers are they aside from being stereoisomers?
stereoimers not related as mirror images at all
GEOMETRIC ISOMERS - cis & trans compounds
RACEMIC MIXTURES
- mixtures containing _____ _____ of a __ of _____
- represented as (2)??
- optical activity + reason
- equimolar quantities of a pair of enantiomers
- (±) or (dl)
- optically inactive due to cancelling out of optical rotations
ENANTIOMERS vs DIASTEREOMERS in terms of
- physical properties
- chemical properties
ENANTIOMERS
- identical physical properties EXCEPT in their optical orientation
- identical chemical properties EXCEPT toward optically active reagents
DIASTEREOMERS
- different physical and chemical properties
GEOMETRIC ISOMERISM
- what type of organic molecules exhibit this? + reason
- 2 types
- interconvertible or not?
- alkenes and cycloalkanes ONLY due to restriction in movement/rotation (double bond + ring)
- cis* (same side orientation)
- trans* (different side orientation)
*Italicized
- not interconvertible
APPLICATIONS
Natural products (2)
Drugs (3)
Biological activity (1)
NP:
1. (S) - carvone: caraway odor
(R) - carvone: spearmint odor
- (d) - limonene: orange odor
(l) - limonene: lemon odor
DRUGS:
1. (S) - naproxen: anti-inflammatory agent
(R) - naproxen: liver toxin
- (R/S) - fluoxetine: effective anti-depressant but cannot prevent migraines
(S) - fluoxetine: effective for preventing migraines - (R/S) - ibuprofen: snow analgesic + anti-inflammatory agent
(S) - ibuprofen: active analgesic + anti-inflammatory agent
BIOLOGICAL ACTIVITY:
1. (d) - thalidomide: cures morning sickness
(l) - thalidomide: teratogenic substance
MOST IMPORTANT THING TO REMEMBER WHEN CHECKING enantiomers
check if CHIRAL muna yung molecule
MOST IMPORTANT THING TO REMEMBER WHEN CHECKING for presence of plane of symmetry?
try to rotate the bonds (if may forward and backward) and see if possible maging same
