OCHEM (needs editing)

What is a Lewis structure?

A diagram that shows all valence electrons, bonds, and lone pairs in a molecule.

What is a bond‑line (zigzag) structure?

A shorthand structure where carbon atoms are at line ends/vertices and hydrogen atoms on carbons are implied.

What is the formula for formal charge?

FC = valence electrons – (lone pair electrons + ½ bonding electrons).

How do you determine an atom’s hybridization?

Count the number of regions of electron density (atoms + lone pairs) around it.

What is sp hybridization?

2 electron groups; linear geometry; 180° bond angle.

What is sp² hybridization?

3 electron groups; trigonal planar; 120° bond angle.

What is sp³ hybridization?

4 electron groups; tetrahedral geometry; 109.5° bond angle.

What is a sigma (σ) bond?

A bond formed by head‑on overlap of orbitals; every single bond contains one σ bond.

What is a pi (π) bond?

A bond formed by sideways overlap of unhybridized p orbitals; found in double/triple bonds.

Which orbital has the most energy: sp, sp², or sp³?

sp³ has the most energy; it has more p‑character.

What is a conjugate base?

The species formed after an acid loses a proton (H⁺).

What is CHESIRE used for?

To compare acidity/basicity using: Charge, Hybridization, Electronegativity, Size, Induction, Resonance

Define acid and base (Brønsted‑Lowry).

Acid = proton donor; Base = proton acceptor.

What makes a strong acid?

A low pKa value and a stable conjugate base.

What makes a strong base?

A high pKa of its conjugate acid; strong tendency to accept a proton.

How do you identify the strongest acid?

Look for the molecule with the lowest pKa.

How do you identify the strongest base?

Find the conjugate base of the weakest acid (highest pKa).

What happens when an acid reacts with a base?

A proton is transferred to form the conjugate base and conjugate acid.

When is a molecule protonated?

When pH < pKa.

When is a molecule deprotonated?

When pH > pKa.

How do you draw a protonated form at a certain pH?

Add an H⁺ to the basic site if pH < pKa.

What’s the electron pair geometry of an sp³ atom?

Tetrahedral.

What’s the bond angle of an sp² atom?

~120°.

What is the pKa of water?

Approximately 15.7.

What is the pKa of a carboxylic acid?

~4–5.

How do you use a pKa chart?

Compare acids’ pKa values; equilibrium favors side with weaker acid (higher pKa).

What is the Keq expression for acid‑base reactions?

Keq = 10^(pKa of acid on left – pKa of acid on right).

What is a strong acid example?

HCl, HNO₃, H₂SO₄ (very low pKa).

Is nitrogen typically acidic or basic?

Basic, especially in amines.

What is induction?

Electronegative atoms pull electron density, stabilizing negative charges through sigma bonds

What is resonance?

Delocalization of charge using pi bonds

How does size affect acidity?

Larger atoms stabilize negative charge better → stronger acids (size goes down and to the right on the periodic table)

Name 5 functional groups.

Alcohol, alkene, ketone, carboxylic acid, amine.

What’s the hybridization of the oxygen in a carbonyl group?

sp².

What kind of orbitals overlap in a pi bond?

Unhybridized p orbitals.

How many sigma and pi bonds in a single bond?

1 sigma bond

How many sigma and pi bonds in a double bond?

1 sigma, 2 pi

How many sigma and pi bonds in a triple bond?

1 sigma, 2 pi

What is a protonated form?

Has H+, If pH < pKa → mostly protonated

What is the deprotonated form?

Missing H+, If pH > pKa → mostly deprotonated

What is the quick way to identify hybridization?

Assume all non hydrogens are sp³ hybridized, then remove a p for every pi bond (1 for a double, 2 for a triple)

What do strong bases have?

high pKa values, very unstable, less electronegative, smaller atoms, sp3 orbitals

What do strong acids have?

low pKa values, stable, more electronegative, bigger atoms, sp orbitals