Organic Chem 1 - Exam 1

Chapters 1, 2, 3

How many bonds does carbon form

4

Sigma (𝜎) bonds

direct overlap of orbitals

Pi (𝛑) bonds

side by side overlap of p orbitals

How many valence electrons does carbon have

four (2s²2p²)

How many valence electrons does nitrogen have

five (2s² 2p³)

sp³ hybrid orbitals have ___ bonds and a ___ structure

4, tetrahedral (109º)

sp² hybrid orbitals have ___ bonds and a ___ structure

3, trigonal planar (120º)

sp hybrid orbitals have ___ bonds and a ___ structure

2, linear (180º)

To find hybrid type…

Count the number of sigma bonds and non-bonded electrons around carbon atoms (pi bonds don’t count)

How many sigma bonds are in a double(or more) bond?

One

What does the shape of a skeletal structure depend on?

Bond angles

Polar covalent bond definition

The bonding election are attracted more strongly by one atom than the other (electron distribution isn’t symmetrical)

Electronegativity (EN) definition

THe ability of an atom to attracted the shares electrons in a covalent bond

Bond polarity is due to…

Differences in electronegativity

Metals on the left side of the period table attract electrons…

weakly, giving them a lower electronegativity

Oxygen, nitrogen, and halogens on the right side of the periodic table attract electrons…

strongly, giving them a higher electronegativity

Carbon has an electronegativity of…

2.5

Rough bond electronegativity guide:

• Differ > 0.5 = non-polar covalent

• Differ 0.5 ≤ x ≤ 2 = polar covalent

• Differ > 2 = largely ionic

Electrostatic potential maps definition

Use color to show electron rich (red: 𝛅-) and electron poor (blue: 𝛅+) regions in a molecule

Inductive effect definition

The shifting of electrons in a sigma bond in response to the EN of nearby atoms

Strongly polar substances are often soluble in…

polar solvents (like water)

Less polar substances are ___ in water

Insoluble

Dipole moment definition

The magnitude of the change, Q, at either end of the molecular dipole times the distance, r, between the charges

Formal charge definition

The hypothetical charge (usually abnormal) assigned to an atom in a molecule

How to calculate formal charge

(# of valence electrons in free atom) - (# of valence electrons in bonded atom)

Resonance definition

Way to describe the bonding in certain molecule or ions when a single Lewis structure can’t show true electron arrangement

Resonance hybrid definition

Ions with resonance forms have a single unchanging structure of the two individual forms and characteristics of both

Resonance form rules:

1. Individual resonance forms are imaginary, not real

2. Resonance forms differ only in the placement of their pi bonds or nonbonding electrons

3. Different resonance forms of a substance don’t have to be equivalent

4. Resonance forms obey normal rules of valency

5. The resonance hybrid is more stable than any individual resonance form

Brønsted-Lowry acid definition

A substance that donates a hydrogen ion

Brønsted-Lowry base definition

A substance that accepts a hydrogen ion

Conjugate base definition

What remains after an acid donates a hydrogen ion during a Brønsted-Lowry reaction

Conjugate acid definition

What is formed when a base accepts a hydrogen ion in Brønsted-Lowry reaction

Relationship for pKa

Lower the pKa, the stronger the acid
Higher the pKa, the weaker the acid