Orgo Quiz 1

Question 1

determining sigma vs pi MOs

Answer 1

• sigma MOs have most e- density along axis between nuclei, pi MOs have it above/below

Question 2

determining bonding vs antibonding MOs

Answer 2

• bonding MOs have most e- density betwen nuclei, antibonding MOs have most on either side

Question 3

resonance structures

Answer 3

Lewis structures with delocalized electrons; real structure is a “hybrid” that is more stable than any contributor

Question 4

nonidentical resonance structures

Answer 4

• resonance structures that often have more formal charges and more lone pairs compared to bonds
• contribute unevenly to the nature of the hybrid (minor contributors)

Question 5

rules for writing resonance structures

Answer 5

1. only position of pi bonds and lone pairs can change
2. all resonance contributors must be proper Lewis contributors (no more than 4 bonds on period 2 elements)
3. more bonds is better than more lone pairs (and group 3+ elements can have >4 bonds)
4. spread out electrons; smaller formal charges are better
5. negative FCs are more stable on more electronegative atoms

Question 6

hybridized orbitals for different 3D structures

Answer 6

• tetrahedral: sp3
• trigonal planar: sp2
• linear: sp