MCAT Organic Chemistry Complete Study Notes & Practice Questions
2026 | Rated A+
Electrostatic Forces - CORRECT ANSWER✔✔The attractive force between
electrons and the nuclei that is responsible for all molecular bonds.
Coordinate Covalent Bond - CORRECT ANSWER✔✔One nucleus donates both of
the electrons in the bond.
Hybridization - CORRECT ANSWER✔✔sp - 180° - linear
sp2 - 120° - trigonal planar
sp3 - 109.5° - tetrahedral, pyramidal, or bent
dsp3 - 90°, 120° - trigonal-bipyramidal, seesaw, t-shaped, linear
d2sp3 - 90° - octahedral, square pyramidal, square planar
When one or more shape is possible, it is determined by the number and position
of the lone pairs of electrons.
Instantaneous Dipole Moment - CORRECT ANSWER✔✔Exists in an otherwise
nonpolar molecule. Occurs because the electrons in a bond move about the
,orbital and at any moment may not be distributed exactly between the two
bonding atoms, even when the atoms are identical.
London Dispersion Forces - CORRECT ANSWER✔✔Occur between two
instantaneous dipoles; the weakest dipole-dipole force (vs. hydrogen bonds which
are the strongest dipole-dipole forces).
Zwitterion - CORRECT ANSWER✔✔A neutral molecule with a positive and
negative electrical charge at different locations within the molecule at a pH of 7.
Ex: amino acids -> amine group deprotonates the carboxylic acid group.
Isomers - CORRECT ANSWER✔✔Molecules that have the same molecular formula
but are different compounds.
Conformational Isomers (Conformers) - CORRECT ANSWER✔✔Not true isomers -
different spatial orientations of the same molecule. At low temperatures, the
anti-conformation is the most common.
Structural Isomers - CORRECT ANSWER✔✔Have the same molecular formula but
different bond-to-bond connectivity; simplest form of isomer.
Stereoisomers - CORRECT ANSWER✔✔Two molecules with the same molecular
formula and same bond-to-bond connectivity that are not the same compound.
Like conformational isomers but contain at least one *chiral/stereo center (C
bonded to 4 different substituents).
,2 types:
- Enantiomers
- Diastereomers
Enantiomers - CORRECT ANSWER✔✔Stereoisomers that have opposite absolute
configurations at EACH chiral center (mirror images). Cannot be separated by
physical means.
When in equal concentrations -> racemic mix.
Resolution = the separation of enantiomers.
Same physical and chemical characteristics except in 2 cases:
1) Reactions with other chiral compounds.
2) Reactions with polarized light.
Diastereomers - CORRECT ANSWER✔✔Stereoisomers that are not mirror images
(are not the same compound). Can be separated by physical means
(crystallization).
Geometric isomer: special type of diastereomer, have different physical
properties.
- Cis: has dipole moment -> strong intermolecular forces so has high boiling point;
lower symmetry does not form crystals as easily so has lower melting point; has
steric hindrance so has higher heats of combustion.
- Trans: no dipole moment - lower boiling point, higher melting point, lower heats
of combustion.
, --> better to use E (Opposite) and Z (same)
Epimer - CORRECT ANSWER✔✔Diastereomers that differ at only one chiral
center.
Anomers - CORRECT ANSWER✔✔Two diastereomers formed from a ring closure
at an epimeric C.
Anomeric carbon: the chiral carbon of the anomer.
Ex: glucose - anomeric C determines if it's α-glucose or β-glucose.
Meso Compounds - CORRECT ANSWER✔✔Optically inactive (achiral) molecule
with two chiral centers; have a plane of symmetry between their centers which
divides the molecule into halves that are mirror images of each other.
Absolute Configuration - CORRECT ANSWER✔✔The only way to absolutely
describe a chiral molecule.
R = rectus: right (clockwise)
S = sinister: left (counterclockwise)
*for when H (or any other 4th priority substituent) is on DASHES.
Mirror images of chiral molecules always have opposite absolute configurations.
2026 | Rated A+
Electrostatic Forces - CORRECT ANSWER✔✔The attractive force between
electrons and the nuclei that is responsible for all molecular bonds.
Coordinate Covalent Bond - CORRECT ANSWER✔✔One nucleus donates both of
the electrons in the bond.
Hybridization - CORRECT ANSWER✔✔sp - 180° - linear
sp2 - 120° - trigonal planar
sp3 - 109.5° - tetrahedral, pyramidal, or bent
dsp3 - 90°, 120° - trigonal-bipyramidal, seesaw, t-shaped, linear
d2sp3 - 90° - octahedral, square pyramidal, square planar
When one or more shape is possible, it is determined by the number and position
of the lone pairs of electrons.
Instantaneous Dipole Moment - CORRECT ANSWER✔✔Exists in an otherwise
nonpolar molecule. Occurs because the electrons in a bond move about the
,orbital and at any moment may not be distributed exactly between the two
bonding atoms, even when the atoms are identical.
London Dispersion Forces - CORRECT ANSWER✔✔Occur between two
instantaneous dipoles; the weakest dipole-dipole force (vs. hydrogen bonds which
are the strongest dipole-dipole forces).
Zwitterion - CORRECT ANSWER✔✔A neutral molecule with a positive and
negative electrical charge at different locations within the molecule at a pH of 7.
Ex: amino acids -> amine group deprotonates the carboxylic acid group.
Isomers - CORRECT ANSWER✔✔Molecules that have the same molecular formula
but are different compounds.
Conformational Isomers (Conformers) - CORRECT ANSWER✔✔Not true isomers -
different spatial orientations of the same molecule. At low temperatures, the
anti-conformation is the most common.
Structural Isomers - CORRECT ANSWER✔✔Have the same molecular formula but
different bond-to-bond connectivity; simplest form of isomer.
Stereoisomers - CORRECT ANSWER✔✔Two molecules with the same molecular
formula and same bond-to-bond connectivity that are not the same compound.
Like conformational isomers but contain at least one *chiral/stereo center (C
bonded to 4 different substituents).
,2 types:
- Enantiomers
- Diastereomers
Enantiomers - CORRECT ANSWER✔✔Stereoisomers that have opposite absolute
configurations at EACH chiral center (mirror images). Cannot be separated by
physical means.
When in equal concentrations -> racemic mix.
Resolution = the separation of enantiomers.
Same physical and chemical characteristics except in 2 cases:
1) Reactions with other chiral compounds.
2) Reactions with polarized light.
Diastereomers - CORRECT ANSWER✔✔Stereoisomers that are not mirror images
(are not the same compound). Can be separated by physical means
(crystallization).
Geometric isomer: special type of diastereomer, have different physical
properties.
- Cis: has dipole moment -> strong intermolecular forces so has high boiling point;
lower symmetry does not form crystals as easily so has lower melting point; has
steric hindrance so has higher heats of combustion.
- Trans: no dipole moment - lower boiling point, higher melting point, lower heats
of combustion.
, --> better to use E (Opposite) and Z (same)
Epimer - CORRECT ANSWER✔✔Diastereomers that differ at only one chiral
center.
Anomers - CORRECT ANSWER✔✔Two diastereomers formed from a ring closure
at an epimeric C.
Anomeric carbon: the chiral carbon of the anomer.
Ex: glucose - anomeric C determines if it's α-glucose or β-glucose.
Meso Compounds - CORRECT ANSWER✔✔Optically inactive (achiral) molecule
with two chiral centers; have a plane of symmetry between their centers which
divides the molecule into halves that are mirror images of each other.
Absolute Configuration - CORRECT ANSWER✔✔The only way to absolutely
describe a chiral molecule.
R = rectus: right (clockwise)
S = sinister: left (counterclockwise)
*for when H (or any other 4th priority substituent) is on DASHES.
Mirror images of chiral molecules always have opposite absolute configurations.
