Organic Chemistry - Exam 1

What are the three functional subatomic particles?

Protons, Neutrons, Electrons

Proton

Positively charges particles located in the nucleus

What do protons determine?

The identity of an element.

Neutron

Uncharged particles that are located in the nucleus

Electron

Negatively charged particles that surround the nucleus and determine the chemical bonding and reactivity of the element.

Aufbau Principle

Orbitals fill in order of increasing energy (lowest energy orbitals fill first)

Pauli Exclusion Principle

A maximum of 2 electrons can occupy a single orbital, and they must have opposite (paired) spins

Hund’s Rule

When filling degenerate orbitals, electrons occupy separate orbitals singly before pairing up.

1s Orbital Shape

Spherical

2s Orbital shape

Spherical with a node at the nucleus

2p Orbital Shape

Dumbbell-shaped with two lobes and a node at the nucleus

Octet Rule

Atoms tend to gain, lose, or share electrons to achieve a stable noble gas electron configuration with a full valence shell

Ionic Bonding

Transfer of electrons between atoms with large differences in electronegativity

Covalent Bonding

Sharing of valence electrons between atoms with similar electronegativity

What rules determine whether a resonance structure is a major or minor contributor to the overall resonance hybrid?

Complete octets

Maximum Bonds

Negative charge on the most electronegative atom

As little charge separation as possible

Empirical Formula

Simplest whole-number ratio of atoms in a compound

Molecular Formula

Shows the actual number of each type of atom in a molecule

A central atom with 4 domains has

Tetrahedral Geometry and bond angles of approximately 109.5 degrees.

A central atom with 3 domains has

Trigonal Planar Geometry and bond angles of approximately 120 degrees.

A central atom with 2 domains has

Linear geometry with bond angles of approximately 180 degrees.

Sigma Bonds

are covalent bonds formed by the direct overlap of s, p or hybridized atomic orbitals, allowing for free rotation around the bond axis.

Pi Bonds

are covalent bonds formed by the side-to-side overlap of p orbitals, restricting rotation around the bond axis.

Sterioisomer

are compounds with the same molecular formula and connectivity but different spatial arrangements of atoms

Constitutional Isomers

are compounds that have the same molecular formula but differ in the connectivity of their atoms

Cis isomer

is a type of stereoisomer where similar substituents are on the same side of a double bond.

Trans Isomer

is a type of stereoisomer where similar substituents are on opposite sides of a double bond.

Node

A region of space where the electron density is zero

Resonance Hybrid

The true, actual structure of a molecule that is a weighted average combination of all valid resonance contributors

Degenerate Orbitals

are orbitals that have the same energy level

Hybridized Orbital

An atomic orbital formed by the combination of two or more atomic orbitals on the same atom

What causes bond dipole moments?

Arises from differences in electronegativity between two bonded atoms

What causes Molecular Dipole Moments?

The vector sum of all individual bond dipoles and lone pair contributions

How do lone pairs affect dipole moments?

Unshared electron pairs contribute significantly to the magnitude and direction of the overall molecular dipole moment

What are the three primary attractive intermolecular forces?

London Dispersion Forces

Dipole-Dipole Interactions

Hydrogen Bonding

London Dispersion Forces

Transient/induced dipoles and the main force in nonpolar molecules

Dipole-Dipole Interactions

Permanent electrostatic attraction between polar molecules.

Hydrogen Bonding

Particularly strong dipole–dipole attraction occurring when H is directly bonded to highly electronegative O or N

How does carbon chain branching affect the boiling point of alkanes?

Branching makes the molecule more compact and decreases its SA, therefore lowering the boiling point

Which side of an acid–base reaction is favored at equilibrium?

formation of the weaker acid and the weaker base

What are the 5 key structural factors used to predict Brønsted acid strength?

Electronegativity

Anion Size

Inductive Effects

Hybridization

Resonace

Nucleophile

An electron rich species that donates an electron pair to form a chemical bond in a reaction.

Electrophile

An electron poor species that accepts an electron pair from a nucleophile during a chemical reaction.

Bronsted-Lowry Acid

Any species capable of donating a proton

Bronsted-Lowry Base

Any species capable of accepting a proton

Lewis Acid

Any species capable of accepting an electron pair to form a new covalent bond

Lewis Base

Any species capable of donating an electron pair to form a new covalent bond.

Conjugate Acid–Base Pair

Two chemical species that differ from each other only by the presence or absence of a single proton

Inductive Effect

The pull of electron density through sigma-bonds caused by differences in electronegativity of nearby atoms.

What are the IUPAC prefix rules for carbon chain lengths 1 through 10

• Find the longest continuous carbon chain.

• Number the chain starting from the end closest to a substituent branch.

• Identify and name substituents (alkyl groups) with location numbers.

• Alphabetize substituents (ignoring prefixes)

What is a Primary carbon?

Carbon bound to 1 other carbon

What is a secondary carbon?

Carbon bound to 2 other carbons

What is a Tertiary Carbon

Carbon bound to 3 other carbons

What is a quaternary Carbon?

Carbon bound to 4 other carbons

Newman Projection

A view looking directly down a specific C—C bond axis. The front carbon is represented by a point where three bonds meet, and the back carbon is represented by a circle.

Dihedral Angle

The angle between two planes defined by two sets of three atoms, often used in the context of molecular conformation.

Staggered conformation

dihedral angle of 60 degrees, where atoms or groups on adjacent carbons are spaced as far apart as possible, minimizing steric strain.

Eclipsed Conformation

A molecular conformation where atoms or groups on adjacent carbons are directly aligned with each other, resulting in a dihedral angle of 0 degrees and increased steric strain.

Anti Conformation

A specific type of staggered conformation where two largest substituents are positioned 180 degrees apart,

Gauche Conformation

a type of staggered conformation where two substituents are positioned 60 degrees apart, leading to some steric strain.

Eclipsed Conformation

a molecular conformation where atoms or groups on adjacent carbons are aligned, resulting in high steric strain.

Totally Eclipsed Conformation

a conformation where substituents are aligned with each other, resulting in maximum steric strain.

Angle Strain

Strain caused by compression or expansion of bond angles away from the ideal tetrahedral angle

Torsional Strain

Strain that arises from the repulsion between eclipsed bonds

Steric Strain

Strain caused by non-bonded atoms being forced closer together than their van der Waals radii allow.

Axial Bonds

Directed straight up or down, parallel to the ring's vertical axis of symmetry.

Equatorial Bonds

Directed outward around the equator of the ring, roughly in the plane of the ring pointing slightly up or slightly down.

What are the four primary types of organic chemical reactions?

Additions

Eliminations

Substitutions

Rearrangements

Addition Reactions

Two reactants combine to form a single product

Elimination Reactions

A single reactant splits into two products

Substitution Reactions

Two reactants exchange parts to form two new products.

Rearrangement Reactions

A single reactant undergoes a reorganization of bonds and atoms to yield an isomeric product.

Enthalpy

Measures bond energies and the heat released or absorbed during a reaction

Entropy

Measures the change in system disorder/freedom of motion.

Bond Disassociation Energy

The amount of energy required to break a covalent bond homolytically in the gas phase.

Activation Energy

The minimum energy barrier reactants must overcome to reach the transition state and convert to products.

Catalyst

A substance that increases the rate of a chemical reaction by lowering the activation energy without being consumed in the process.

Transition State

The highest energy state during a reaction where reactants are transformed into products. It is an unstable state that can only be maintained for a very short time.

Reaction Intermdiate

A fleeting species formed during the transformation of reactants to products, existing between these states in the reaction pathway.

Hammond Postulate

Species that are close in energy on a reaction coordinate are also close in structure.