Topic 4: Acid & Base pt 3 Flashcards
(3) Resonance Stabilization Affects Acidity?
Use the steps to configure the resonance and the one with grater amounts is the highest and the one with the lowest resonance is the weakest.
An example: Competitive Bases & Resonance
Many organic molecules have 2 or more sites that can acts as a proton acceptor.
Ex: Acetic Acid can be protonated at 2 sites.
Pi bonding electrons converted to non-bonding.
* Non-bonding electrons convert to pi bonding
Which CA is favored?
The more stable one!Which is that?
Recall resonance provides additional stability by moving pi or non-bonding electrons
An example: Competitive Bases & Resonance
Comments on the importance of the resonance structures.
1.All atoms obey the octet rule.
2.The carbon is electron deficit - 6 electrons, not 8. Lesser importance.
** ALL ATOMS OBEY OCTET RULE***
(4) Substituents Affect the Strength of the Acid?
Ex: Which of the following compounds is the strong acid?
- Inductive and Electrostatic Stabilization
Due to electronegativity of F small positive charges build up on C resulting in stabilization of the anion.
Effects drops off with distance (after 3 carbons, no inductive effect)
Problem: Which following compound is the strongest acid?
Due to the electronegativity of Br small positive charges build up on C resulting in the stabilization of the anion.
**Effects drops off with distance (after 3 carbons, no inductive effect)
* The one with less carbons away is the most acidic
(5) Hybridization Affects Acidity
Relative electronegativities of carbon
sp(triple bond) >sp ^2 (double bond) > sp^3 (single bond)
More s character, more stability, more “electronegative”
Electronegativity affects acidity…
Ex: HC≡CH , H2C=CH2, H3C-CH3
Which one is a strong acid?
- Hybridization of the atom bearing the charge.
sp>sp2>sp3
Bottom line: More s character, more stability, more “electronegative”, H-A more acidic, A- less basic.
