Chapter 3: Acids and Bases, Klein

What are HA and A-?

HA is an acid because it has a proton to donate, while A- is a base because it lacks a proton and would like one

How much is HA willing to give up its proton?

If HA is a strong acid, then it will give it up easily, but if it is weak, it will take more pull.

What are the four factors (in order) that cause a stabilization in charge?

ARIO!

Atom electronegativity & size

Resonance

Inductive Effect

Orbitals

Why is it important that we stabilize the charge?

Basically, for us to be able to tell whether an acid is strong or not, we must look at its conjugate base. The more stable a base is, the less reactive it is, meaning it is a much weaker base as it is not looking to get into contact with other molecules. This means that the acid must be very strong, and vice versa.

Can you explain factor 1 (atom) in more detail?

Going across a row, if two atoms are comparable, the more right you go, the more electronegative it is, and therefore the more stable it is. Size is comparable going down a column. The more down you go, the bigger the size of the atom, and the more stable the charge as it is stabilized across a bigger area.

Can you explain factor 2 (resonance) in more detail?

The more resonance there is in a structure near the charge, the more stable the base is. If there is more resonance, the charge is able to be distributed to more molecules and the charge is not concentrated on one atom, delocalized electrons.

Delocalized Electrons

Spreading charge over multiple atoms

What is the second rule with more clarification?

While the more delocalized the electrons, the better, a charge spread over atoms is more stable than a charge spread over 2 atoms is more stable, but 2 Oxygens is better than four Carbons.

Can you explain factor 3 (induction) in more detail?

Induction: pulling of electron density by more electronegative atoms causing a more prominent difference in electronegativity (extra positive Carbon) which causes it to have a pull towards the negative charge, further delocalizing it

Can you explain factor 4 (orbitals) in more detail?

Each hybridized orbital has a difference size. sp3 is very long, sp2 is medium, and sp is very short. If there is a triple bond and single bond, this means that the orbital is sp hybridized. When this occurs, the sp orbitals are very small so they will hold the lone pair/electrons much closer to them stabilizing them as they do not want to let go, as they have a stronger pull than a sp3 hybridized orbital. The smaller the orbital, the greater the stability, as these orbitals are able to attract greater pull by the nucleus.

*What is the one exception to the four in-order rule?

An sp hybridized orbital of Carbon having a negative charge vs. a Nitrogen having a negative charge on it. While we should compare the electronegativities, we are actually going to consider orbitals first.

*What is another factor?

Solvating effect: bulky molecules experiences fewer interactions with the solvent molecules, but these interactions are stabilizing, as they aren’t as reactive.

Explain pKa

It is a quantitative measure to tell how strong/weak an acid is. The smaller the pKa, the more acidic the molecule is, and vice versa.

How can we use charge stability to predict the position of equilibrium?

To determine, compare the two bases. Whichever base is more stable means it is more okay with maintaining its position with a negative charge, so that side is more favored than a side with the other base having the electronegative charge.

*How do you depict this with arrows?

Show an elongated arrow going to the side of favorability, while a shorter one on the other side. This means that most of the time, they will favor that side.

Mechanism

Shows how electrons move during a reaction to form products

What do you use to show mechanisms?

Curved arrows, differing from ones previously.

How are they similar or different from curved arrows shown previously in terms of rules?

While you must maintain the octet rule, you can break single bonds, because you use the arrows to show what happened (breaking bonds) in a reaction.

How do you push arrows on an acid base reaction?

It is overall the same. You always have 2 arrows, pushing one from the lone pair on the base to the Hydrogen on the strong acid, and another from the bond between the atom attached to the Hydrogen to the atom attached to the Hydrogen.