Trends of Acidity/Basicity

Question 1

What are the trends ranked from most important to least important?

Answer 1

1. Electronegativity
2. Size
3. Resonance
4. Induction
5. Hybridization

Question 2

When it comes to acidity, what is important to remember?

Answer 2

It’s all about the stability of the charged species. (e.g. oxygen can stabilize/handle the negative charge better than the less electronegative atom)

Question 3

Electronegativity trend

Answer 3

As electronegativity increases, acidity increases; trend only works in a row of the periodic table (atoms have to be in the same)

Question 4

Size trend

Answer 4

As the size of the molecule increases, acidity increases; trend only works if atoms are in the same column of periodic table

Question 5

Resonance

Answer 5

As resonance increases, acidity increases; negative charge is stabilized through resonance so if you’re able to draw more resonance structures, the more acidic it is

Question 6

Induction trend

Answer 6

“Dyson vacuum cleaner”; halogens act like vacuum cleaners because they create a dipole between itself and the atom attached to it; has smaller effect than resonance; the more dipoles created, the more partial positive charge created–>more acidic; if he number of “vacuums” are equal between two molecules, then the ones closer to the negative charge will be more acidic; some halides can pull more than others due to electronegativity

Question 7

Hybridization trend

Answer 7

The molecule with more s-character is more acidic. sp3 has 25% s-character, sp2 has 33% s-character, sp has 50% s-character–>sp molecule is more acidic

Question 8

Determining the most acidic proton

Answer 8

Look for trends

Question 9

Determining the strength of a base

Answer 9

Look at pka of the conjugate acid; weaker conjugate base–>strong base and strong conjugate acid–>weak base

Question 10

Lewis acid/base reaction mechanism

Answer 10

2 arrows- 1 arrows starts at electron source (lone pair/pi bond) and points to electron sink (tends to be hydrogen since it has a partial positive charge); the other arrow will start at the bond that’s being broken and points to where those electrons from that bond will be going to)

Question 11

Bronsted acid/base reaction mechanism

Answer 11

1 arrow- shows where bond is being made (starts at electron source and points to electron sink)