Class 1 Flashcards
When is a molecule unsaturated?
When there is at least 1 pi bond or ring
1 pi bond = 1 degree of saturation
2 pi bonds = 2 degrees, etc.
How do you calculate degree of unsaturation?
DOU = (2n + 2 - x)/2
n= number of carbons x= number of hydrogens
- Treat halogens like hydrogens
- Ignore oxygens
- Subtract the number of Nitrogens from x and then apply
What are properties of unstable molecules
High in energy
Reactive with environment
Shorter lifetimes
What are properties of stable molecules
Low in energy
Less reactive with environment
Longer lifetimes
What is the ideal bond angle?
109.5 degrees, smaller than that = ring strain
What is the typical donating group/subsitituent?
Alkyl group
As such, alkyl R groups will push electrons away and thus stabilize a cation and destabilize an anion.
What are typical withdrawing (EN) groups?
O, N, halogens
What are three principles about resonance structures?
- Generally, more resonance structures = greater stabilization
- Delocalization can only occur through ADJACENT p orbitals!
- Lowest energy (most stable) resonance structures contribute most to hybrid
What three factors indicate the best resonance structure?
- The octet rule satisfied for ALL atoms!!!!!!!!
- The least formal charge
- Neg charge on more EN atoms
What is the most stable type of cation?
Tertiary!
What is required to have resonance structures?
A pi bond!
What defines a Bronsted-Lowry acid?
Wants to donate a H+ and leave behind a conjugate base.
What 3 factors affect acid strength and how?
By stabilizing the conjugate base:
- Electronegativity -> more EN atoms handle negative charge better.
- Resonance structure for anion conjugate base
- Induction
What is a Lewis base?
Nucleophile (negatively charged an/or lone pair of e- to donate)
Think LEWis NUcleophile
Nucleophiles are Lewis ________.
Bases
What are some nucleophilic trends?
When comparing the same atom, a negative charge makes a stronger nucleophile
For atoms in the same row, nucleophilicity increases as electronegativity DECREASES
For atoms in the same column, nucleophilicity increases as size increases (down the periodic table)
Electrophiles are typically electron ______.
Deficient
Electrophiles are Lewis ______
Acids