1. Acids and Bases: Functional Groups (Part 2)
Organic Chemistry, 8th Edition L. G. Wade, Jr.
Chapter 2 Lecture
Acids and Bases: Functional Groups (Part 2)

2. Lecture 6: Acids & Bases (Part II): Lewis System, Hydrocarbons, Functional Groups
Just in Time (A First Look)
Quantifying Acidity without a Table
The Steps to the Acronym “ARIO”
Lewis Acids and Bases
Nucleophiles and Electrophiles
Curved Arrow Notation
Hydrocarbons & Functional Groups

3. JIT Conjugate Base?

4. Quantifying Acidity without a Table
The more effectively a conjugate base can stabilize its negative charge, the stronger the acid.
What factors affect the stability of a negative formal charge?
The type of Atom that carries the charge
Resonance
Induction
The type of Orbital where charge resides
These factors can be remembered by the acronym ARIO

5. Quantifying Acidity without a Table
ARIO – The type of atom that carries the charge
More electronegative atoms are better at stabilizing negative charge.
Compare the acidity of the two compounds below.

6. Effect of Electronegativity on pKa
As the bond to H becomes more polarized, H becomes more positive and the bond is easier to break.
Across a row, look at the electronegativity

7. Effect of Size on pKa
When looking at atoms in same column, compare the sizes!
As size increases, the H is more loosely held and the bond is easier to break.
A larger size also stabilizes the anion.

8. Quantifying Acidity without a Table
ARIO – Resonance can greatly stabilize a formal negative charge by spreading it out into partial charges
Compare the acidity of the two compounds below by comparing the stabilities of their conjugate bases. How does resonance play a role?
Which acid is stronger?
To answer question, draw the conjugate bases for each along with any resonance forms that may exist.

9. Resonance
Delocalization of the negative charge on the conjugate base will stabilize the anion, so the substance is a stronger acid.
More resonance structures usually mean greater stabilization.
Let’s compare acetic acid with methanesulfonic acid (HOSO2CH3) in terms of acid strength.
Which one is stronger? Explain.

10. Effect of Resonance on pKa
If the negative charge on an atom can be delocalized over two or more atoms, the acidity of that compound will be greater than when the negative charge cannot be delocalized.
The ethoxide anion is less acidic than the acetate ion simply because the acetate ion can delocalize the negative charge.
Methanesulfonic acid can delocalize the charge in three different resonance forms, making it more acidic than the acetate ion.
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Chapter 1

11. Quantifying Acidity without a Table
ARIO – Induction can also stabilize a formal negative charge by spreading it out. How is induction different from resonance?
Compare the acidity of the two compounds below by comparing the stabilities of their conjugate bases. How does induction play a role?
Acetic Acid Trichloroacetic acid

12. Quantifying Acidity without a Table
Explain the pKa differences below

13. Quantifying Acidity without a Table
ARIO – The type of Orbital also can affect the stability of a formal negative charge.
A negative charge is more stable if it is held closely to an atom’s nucleus.

14. Quantifying Acidity without a Table
Compare the acidity of the compounds below by comparing the stabilities of their conjugate bases How does the type of orbital play a role?
pKa =

15. Lewis Acids and Bases Lewis acid/base definition
A Lewis acid accepts and shares a pair of electrons
A Lewis base donates and shares a pair of electrons
Acids and Bases in Bronsted-Lowry world are also the same in Lewis system.

16. Lewis Acids and Bases Lewis Acids are electron pair acceptors
Lewis Bases are electron pair donors
In Lewis acid-base theory, the attraction of oppositely charged species is fundamental to reactivity.

17. Nucleophiles and Electrophiles
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Chapter 1

18. Nucleophiles and Electrophiles
Nucleophile: Donates electrons to a nucleus with an empty orbital.
Electrophile: Accepts a pair of electrons.

19. Classes of Compounds Classifications are based on functional group.
Part of the molecule where reactions usually occur
Three broad classes:
Hydrocarbons: Compounds composed of only carbon and hydrogen.
Compounds containing Oxygen.
Compounds containing Nitrogen.
Chapter 2 19

20. Hydrocarbons Alkanes: single bonds, sp3 carbons.
Cycloalkanes: sp3 carbons form a ring.
Alkanes and cycloalkanes are not considered functional groups!
Alkenes: double bond; sp2 carbons.
Cycloalkenes: double bond in a ring.
Alkynes: triple bond; sp carbons.
Aromatic: (Arenes): contains a benzene ring.
Chapter 2 20

21. Compounds Containing Oxygen
Alcohols: R-OH
Ethers: R-O-R´
Aldehydes:
Ketones:
Chapter 2 21

22. Compounds Containing Oxygen: Carboxylic Acids & Their Derivatives
Acid Chloride:
Ester:

23. Compounds Containing Nitrogen
Amines: RNH2, RNHR´, or R3N
Amides: RCONH2, RCONHR´, RCONR2
Nitriles: RCN
Chapter 2 23

24. Skill Building: Practice Problems
Problem 2-12 thru 2-27

25. Chapter Problems Problem Set 1: 21, 23, 25-27, 31, 33 (a,b)