Organic Chemistry

Alcohols Nomenclature

Alcohols Nomenclature

Suffix -ol

Alcohols with two hydroxyl groups are called diols or glycols and are indicated with the suffix -diol

Aldehydes Nomenclature

Suffix -al

Methanal: Formaldehyde

Ethanal: Acetaldehyde

Propanal: Propionaldehyde

Ketones Nomenclature

Suffix -one

Carboxylic Acid Nomenclature

Suffix -oic acid

Esters Nomenclature

___ -yl ____-oate

Amide Nomenclature

Suffix -amide

Anhydride Nomenclature

Replace acid with anhydride

Isomer

Same molecular formula but different structures

Constitutional (Structural) Isomers

Same molecular formula/weight

Stereoisomer

Same structural backbone, differ in how atoms are arranged in space

Conformational Isomer

Differ in rotation around single bonds

Configurational Isomer

Can be interconverted only by breaking bonds

Newman Projection

A molecule is visualized along a line extending through a carbon-carbon bond axis

Staggered Conformation

When two functional groups in a Newman projection are oriented 180 degrees away from each other; AKA lowest-energy state

Anti Conformation

In a Newman projection, when the two largest groups are antiperiplanar (in the same plane, but on opposite sides) to each other; Occurs in a staggered conformation

Gauche Conformation

In a Newman projection, when the two largest groups are 60 degrees apart; Occurs in a staggered conformation

Eclipsed Conformation

In a Newman projection, when two methyl groups are 120 degrees apart and overlap with the hydrogen atoms on the adjacent carbon

Totally Eclipsed Conformation

In a Newman projection, when two methyl groups directly overlap each other with 0 degrees of separation; The molecule’s highest-energy state

Torsional Strain

Occurs when cyclic molecules must assume conformations that have eclipsed or gauche interactions

Nonbonded Strain (van der Waals Repulsion)

Results when nonadjacent atoms or groups compete for the same space; Dominant source of steric strain in the flagpole interactions of the cyclohexane boat conformation

Axial

In the chair conformation, the hydrogen atoms that are perpendicular to the plane of the ring (sticking up or down)

Equatorial

In the chair conformation, the hydrogen atoms that are parallel to the plane of the ring (sticking out)

Diastereomers

When two molecules are chiral and share the same connectivity but are not mirror images of each other because they different at some of their multiple chiral centers

For any molecule with n chiral centers, there are 2ⁿ possible stereoisomers

Optical Activity

When a chiral compound has the ability to rotate plane-polarized light; One enantiomer will rotate plane-polarized light to the same magnitude but in the opposite direction of its mirror image; Racemic mixtures don’t have this; Molecules with this lack a plane of symmetry

Dextrorotatory (d-)

A compound that rotates the plane of polarized light to the right, or clockwise; Labeled (+); Determined experimentally

Levorotatory (l-)

A compound that rotates light toward the left, or counterclockwise; Labeled (-); Determined experimentally

Specific Rotation

Racemic Mixture

When both (+) and (-) enantiomers are present in equal concentration; No optical activity is observed

Cis-Trans Isomers

Type of diastereomer in which substituents differ in their position around an immovable bond, such as a double bond, or around a ring structure, such as a cycloalkane in which the rotation of bonds is greatly restricted; In simple compounds with only one substituent on either side of the immovable bond, we use the terms cis and trans

Meso Compound

A molecule with chiral centers that has an internal plane of symmetry

Relative Configuration

The configuration of a chiral molecule in relation to another chiral molecule

Absolute Configuration

The exact spatial arrangement of atoms or groups in a chiral molecule, independent of other molecules

Cahn-Ingold-Prelog Priority Rules (E and Z Forms)

The alkene is named (Z) if the two highest-priority substituents on each carbon are on the same side of the double bond and (E) if they are on opposite sides

The higher the atomic number, the higher the priority

(R) and (S) Nomenclature

• Step 1: Assign Priority

Higher atomic number = Higher priority

• Step 2: Arrange in Space

Orient the molecule in 3D so that the atom with the lowest priority is at the back of the molecule (Anytime two groups are switched on a chiral carbon, the stereochemistry is inverted; if we switch the lowest-priority group to the back, we need to switch our final answer from (R) to (S), or vice versa)

• Step 3: Draw a Circle

Draw a circle connecting the substituents from 1-3

Counterclockwise = (S)

Clockwise = (R)

S-Orbital

Spherical and symmetrical, centered around the nucleus

P-Orbital

Composed of two lobes located symmetrically about the nucleus and contains a node—an area where the probability of finding an electron is zero—at the nucleus

D-Orbital

Composed of four symmetrical lobes and contains two nodes; Four of these orbitals are clover-shaped, and the fifth looks like a donut wrapped around the center of a p-orbital

Molecular Orbitals

When two atomic orbitals combine

Bonding Orbital

Produced when the signs of the wave functions of two atomic orbitals are the same; Lower-energy and more stable

Antibonding Orbital

Produced when the signs of the wave functions of two atomic orbitals are different; Higher-energy and less stable

Single Bonds

All of these are sigma bonds, accommodating two electrons; Requires more energy to break this than one of the two bonds in a double bond

Double Bond

One pi bond on top of an existing sigma bond; Hinders free rotation of atoms around the bond axis; Shorter than a single bond

Hybrid Orbitals

Formed by mixing different types of orbitals

S Character

Example Problem: an sp³ orbital has 25% s character and 75% p character