1. Organic Chemistry Second Edition Chapter 1 David Klein
A Review of General Chemistry: Electrons, Bonds, and Molecular Properties
Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.
Klein, Organic Chemistry 2e

2. Organic Chemistry
The study of carbon-containing molecules and their reactions
What happens during chemical reaction?
A collision
Bonds break/form
WHAT IS A BOND?
WHY do reactions occur?
ELECTRONS are the glue
Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.
Klein, Organic Chemistry 2e

3. Structural Theory
Atoms that are most commonly bonded to carbon include N, O, H, and halides (F, Cl, Br, I).
With some exceptions, each element generally forms a specific number of bonds with other atoms
Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.
Klein, Organic Chemistry 2e

4. Structural Theory
Atoms that are most commonly bonded to carbon include N, O, H, and halides (F, Cl, Br, I).
Occurs in Chemistry, Biological Chemistry, every living organism, neuroscience...
Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.
Klein, Organic Chemistry 2e

5. Covalent Bonding
A covalent bond is a PAIR of electrons shared between two atoms. For example…
Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.
Klein, Organic Chemistry 2e

6. Covalent Bonding How do potential energy and stability relate?
What forces keep the bond at the optimal length?
Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.
Klein, Organic Chemistry 2e

7. Atomic Structure A review from General Chemistry
Protons (+1) and neutrons (neutral) reside in the nucleus
Electrons (-1) reside outside the nucleus. In orbitals
Some electrons are close to the nucleus and others are far away. 1s, 2s, 2p, 3s, 3p, 4s, 3d
Which electrons are the valence electrons of carbon?
Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.
Klein, Organic Chemistry 2e

8. Counting Valence Electrons
Valence electrons: For Group A elements only: Group number on the periodic table

9. Simple Lewis Structures
For simple Lewis Structures…
Draw the individual atoms using dots to represent the valence electrons.
Put the atoms together so they share PAIRS of electrons to make complete octets (or duet for H)
Take NH3, for example…
Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.
Klein, Organic Chemistry 2e

10. Simple Lewis Structures
Try drawing the structure for C2H2
Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.
Klein, Organic Chemistry 2e

11. Formal Charge unbalanced or FORMAL charge results in ions
Calculate FORMAL charge
calculate valence electrons that atom should have
calculate valence electrons atom actually has
has
Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.
Klein, Organic Chemistry 2e

12. Formal Charge Calculate the formal charge on each atom. or
Carbon should have 4 valence electrons.
Carbon actually has 8 (octet) valence electrons. 4 count towards its charge.
Neutral C should actually have 4 valence e–
so NO formal charge (neutral)
Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.
Klein, Organic Chemistry 2e

13. Formal Charge Analyze the formal charge of the oxygen atom. or
Oxygen should have 6 valence electrons.
It actually has 8 (octet) valence electrons. 7 count towards its charge.
Neutral O should have 6 e–, but it actually has 7
formal charge is -1
Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.
Klein, Organic Chemistry 2e

14. Polar Covalent Bonds Covalent bonds between atoms: polar or nonpolar
Nonpolar Covalent Bonds: electrons shared evenly
Polar Covalent Bonds: electrons shared unevenly
Electronegativity - how strongly nucleus attracts electrons
Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.
Klein, Organic Chemistry 2e

15. Polar Covalent Bonds
Electrons tend to shift away from lower electronegativity atoms to higher electronegativity atoms.
The greater the difference in electronegativity, the more polar the bond.

16. Atomic Orbitals General Chemistry review
The type or orbital be identified by its shape
An orbital is a region where there is a calculated 90% probability of finding an electron. The remaining 10% probability tapers off as you move away from the nucleus
Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.
Klein, Organic Chemistry 2e

17. Atomic Orbitals Electrons: behave as particles and waves.
The theory matches experimental data
Like a wave on a lake, an electron’s wavefunction can be (+),
(–), or ZERO.
Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.
Klein, Organic Chemistry 2e

18. Atomic Orbitals
Mathematics defines wavefunctions: orbital regions can also be (–), (+), or ZERO
The sign of the wave function is not electrical charge.
p-orbital has (–), (+), and nodal plane (0).
Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.
Klein, Organic Chemistry 2e

19. Atomic Orbitals
1s orbital electrons are most stable (lowest in energy)
The 1s orbital is full once there are two electrons in it.
The 2s orbital is filled next. The 2s orbital has a node.
Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.
Klein, Organic Chemistry 2e

20. Atomic Orbitals
Once the 2s is full, electrons fill into the three degenerate (equal energy) 2p orbitals
The nodes are the “pinch” points
Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.
Klein, Organic Chemistry 2e

21. Atomic Orbitals Common elements and their electron configurations
Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.
Klein, Organic Chemistry 2e

22. Atomic Orbitals The rules that govern our placement of electrons:
AufBau, Hund’s (“hound”) rule, Pauli exclusion (2 of ‘dese
Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

23. Valence Bond Theory
The bond for a H2 molecule results from constructive interference
Where do the bonded electrons spend most of their time?
Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.
Klein, Organic Chemistry 2e

24. Valence Bond Theory A bond: constructive orbital overlap.
Like overlapping waves in Lake Michigan
Only constructive interference results in a bond
Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.
Klein, Organic Chemistry 2e

25. Molecular Orbital Theory
H2 molecule.
Imagine He2, stable or unstable?
Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

26. Hybridized Atomic Orbitals
p orbitals form pi (π) bonds
CONSTRUCTIVE interference = Binding molecular orbital
DESTRUCTIVE interference = Antibonding molecular orbital
MO theory orbitals
Red and blue regions:
parts of the same orbital
Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.