acid and bases

Question 1

how do you compare the strength of an bronsted acid?

Answer 1

1. down the group, the stronger the A-H bond, where HA is the acid, the weaker the acid.
2. the more stable A-, where A- is the conjugate base of HA, the stronger the acid.

Question 2

how do you compare the strength of a bronsted base?

Answer 2

1. the more lone pairs a base has, the stronger of a base it is
2. the greater the charge density of the base, the stronger of a base it is
3. if the lone pairs of a base are delocalised, it is likely to be a weaker base
4. if the lone pairs of a base are on a more EN atom, it is likely to be a weaker base

Question 3

what does pauling’s rule suggest?

Answer 3

each successive dissociation of a multiprotic acid will be around 10,000 times weaker than the last, because it becomes increasingly difficult to form highly negative charged species

Question 4

what is the difference between inductive effects and resonance effects?

Answer 4

1. inductive effects are caused by electronegativity difference, and are generally weak.
2. resonance effects are caused by overlapping p orbitals, and are generally strong

Question 5

how do you compare the strength of a lewis base?

Answer 5

1. the bulkier the lewis base, the more significant the steric effect, and the weaker the base
2. the higher the atomic mass of the lewis base, the weaker the base as lone pairs are further apart
3. if the lone pairs are delocalised, the base tends to be weaker
4. if the lone pairs are from a more EN element, the base tends to be weaker

Question 6

what are the exceptions for lewis acids when comparing inductive and resonance effects?

Answer 6

1. halogen atoms have high electronegativity compared to their size, and thus inductive effects usually dominate
2. in boron lewis acids, resonances dominantes again regardless of the presence of halogen atoms because B has an empty p orbital good for overlapping