Base Equilibrium
BONDING Wize Organic Chemistry Lecture Series, 2017 Presented by: Spencer
BONDING
T E ACH I NG OB J E CT I VES
1. Valence Bond Theory and Hybridization 2. Molecular Orbital Theory
3. Bonding in Delocalized Systems 4. VSEPR 5. Review Questions
BONDING
VAL E NCE B OND T H E ORY AND H Y B R I DI ZATION
Key Idea Valence Bond Theory focuses on the orbitals involved in bonding for each atom in a compound
1s 2s 2p Orbital Drawing
Electron count for carbon: 1s22s22p2
BONDING
VAL E NCE B OND T H E ORY AND H Y B R I DI ZATION
Key Idea Hybridization: s and p orbitals hybridize for every “sigma” (σ) bond
Hybridize!
BONDING
VAL E NCE B OND T H E ORY AND H Y B R I DI ZATION
Hybridize!
BONDING
VAL E NCE B OND T H E ORY AND H Y B R I DI ZATION
Hybridize!
BONDING
VAL E NCE B OND T H E ORY AND H Y B R I DI ZATION
4 x Csp3-H1s σ-bond
2 x Csp2-H1s σ-bond 1 x Csp2-Csp2 σ-bond C2p-C2p π-bond
1 x Csp-H1s σ-bond 1 x Csp-Csp σ-bond 2 x C2p-C2p π-bond
Key Idea: What are the relative C–H bond lengths?
Csp3–H
Csp2–H
Csp–H
BONDING
MOL E CULAR OR B I TAL T H E ORY
Key Idea Molecular Orbital Theory: How the atomic orbitals combine to form bonds
σ-bond
σ*-bond
BONDING
MOL E CULAR OR B I TAL T H E ORY
Key Idea Molecular Orbital Theory: How the (hybridized) orbitals align to form bonds
σ-bond
σ*-bond
BONDING
MOL E CULAR OR B I TAL T H E ORY
Key Idea Molecular Orbital Theory: How the (hybridized) orbitals align to form bonds
π-bond
π*-bond
BONDING
MOL E CULAR OR B I TAL T H E ORY
Key Ideas More electronegative atoms dominate bonding More electropositive atoms dominate antibonding
σ-bond
σ *-bond
BONDING
MOL E CULAR OR B I TAL T H E ORY
Key Ideas More electronegative atoms dominate bonding More electropositive atoms dominate antibonding
π-bond
π*-bond
To break a bond, donate electron density into the antibonding orbital
BONDING
B ONDI NG I N DE L OC ALI ZED SYST E MS
Draw the pi-bonding (or p-orbital overlap) in the following compound
Key Idea: In delocalized systems, there has to be orbital alignment
BONDING
B ONDI NG I N DE L OC ALI ZED SYST E MS
Draw the pi-bonding (or p-orbital overlap) in the following compound
Key Idea: For resonance there has to be orbital alignment
BONDING
B ONDI NG I N DE L OC ALI ZED SYST E MS
What is the hybridization of: O1 ___ O2 ___
BONDING V SE P R
H–C–H: 109.5 °
H–C–C: 120 °
H–C–C: 180 °
Bond angle at Carbon Key Idea VSEPR: Valence Shell Electron Pair Repulsion
BONDING V SE P R
C–C–C:
60 °
90 °
~109.5 °
109.5 °
Bond angle at Carbon
Key Ideas: Ideal C–C–C: 109.5 ° 5 and 6 membered rings are more stable than 3 and 4 membered
BONDING V SE P R
H–C–H: 109.5 °
CH4
H–N–H: 108 °
H–O–H: 104.5 °
NH3
Key Idea VSEPR: Valence Shell Electron Pair Repulsion
H2O
BONDING V SE P R
What are the approximate bond angles at the labelled atoms? 1:_____ 2:_____ 3:_____ 4:_____ 5:_____ 6:_____
BONDING
R E V I E W QUE ST I ONS An organic compound processing an allene is shown below. Answer the following questions:
Draw the orbital overlap for C1, C2, and C3:
What is the hybridization of C1, C2, and C3? Is the correct 3D Dash/Wedge drawn above? Why/ Why not? Can the above compound be chiral?
BONDING
R E V I E W QUE ST I ONS Draw the complete orbital overlap for formamide (shown below). List all the bonds and draw any contributing resonance structures
BONDING
R E V I E W QUE ST I ONS
Which compound has the longest C-Br bond? Which compound has the shortest C-Br bond?
Draw all contributing resonance structures for the following compounds
BONDING
R E V I E W QUE ST I ONS Riboflavin, or vitamin B2, is shown below. What are the approximate bond angles at the labelled atoms
1:_____ 2:_____ 3:_____
4:_____ 5:_____ 6:_____
BONDING
T E ACH I NG OB J E CT I VES
1. Valence Bond Theory and Hybridization 2. Molecular Orbital Theory
3. Bonding in Delocalized Systems 4. VSEPR 5. Review Questions
BONDING
VAL E NCE B OND T H E ORY AND H Y B R I DI ZATION
Key Idea Valence Bond Theory focuses on the orbitals involved in bonding for each atom in a compound
1s 2s 2p Orbital Drawing
Electron count for carbon: 1s22s22p2
BONDING
VAL E NCE B OND T H E ORY AND H Y B R I DI ZATION
Key Idea Hybridization: s and p orbitals hybridize for every “sigma” (σ) bond
Hybridize!
BONDING
VAL E NCE B OND T H E ORY AND H Y B R I DI ZATION
Hybridize!
BONDING
VAL E NCE B OND T H E ORY AND H Y B R I DI ZATION
Hybridize!
BONDING
VAL E NCE B OND T H E ORY AND H Y B R I DI ZATION
4 x Csp3-H1s σ-bond
2 x Csp2-H1s σ-bond 1 x Csp2-Csp2 σ-bond C2p-C2p π-bond
1 x Csp-H1s σ-bond 1 x Csp-Csp σ-bond 2 x C2p-C2p π-bond
Key Idea: What are the relative C–H bond lengths?
Csp3–H
Csp2–H
Csp–H
BONDING
MOL E CULAR OR B I TAL T H E ORY
Key Idea Molecular Orbital Theory: How the atomic orbitals combine to form bonds
σ-bond
σ*-bond
BONDING
MOL E CULAR OR B I TAL T H E ORY
Key Idea Molecular Orbital Theory: How the (hybridized) orbitals align to form bonds
σ-bond
σ*-bond
BONDING
MOL E CULAR OR B I TAL T H E ORY
Key Idea Molecular Orbital Theory: How the (hybridized) orbitals align to form bonds
π-bond
π*-bond
BONDING
MOL E CULAR OR B I TAL T H E ORY
Key Ideas More electronegative atoms dominate bonding More electropositive atoms dominate antibonding
σ-bond
σ *-bond
BONDING
MOL E CULAR OR B I TAL T H E ORY
Key Ideas More electronegative atoms dominate bonding More electropositive atoms dominate antibonding
π-bond
π*-bond
To break a bond, donate electron density into the antibonding orbital
BONDING
B ONDI NG I N DE L OC ALI ZED SYST E MS
Draw the pi-bonding (or p-orbital overlap) in the following compound
Key Idea: In delocalized systems, there has to be orbital alignment
BONDING
B ONDI NG I N DE L OC ALI ZED SYST E MS
Draw the pi-bonding (or p-orbital overlap) in the following compound
Key Idea: For resonance there has to be orbital alignment
BONDING
B ONDI NG I N DE L OC ALI ZED SYST E MS
What is the hybridization of: O1 ___ O2 ___
BONDING V SE P R
H–C–H: 109.5 °
H–C–C: 120 °
H–C–C: 180 °
Bond angle at Carbon Key Idea VSEPR: Valence Shell Electron Pair Repulsion
BONDING V SE P R
C–C–C:
60 °
90 °
~109.5 °
109.5 °
Bond angle at Carbon
Key Ideas: Ideal C–C–C: 109.5 ° 5 and 6 membered rings are more stable than 3 and 4 membered
BONDING V SE P R
H–C–H: 109.5 °
CH4
H–N–H: 108 °
H–O–H: 104.5 °
NH3
Key Idea VSEPR: Valence Shell Electron Pair Repulsion
H2O
BONDING V SE P R
What are the approximate bond angles at the labelled atoms? 1:_____ 2:_____ 3:_____ 4:_____ 5:_____ 6:_____
BONDING
R E V I E W QUE ST I ONS An organic compound processing an allene is shown below. Answer the following questions:
Draw the orbital overlap for C1, C2, and C3:
What is the hybridization of C1, C2, and C3? Is the correct 3D Dash/Wedge drawn above? Why/ Why not? Can the above compound be chiral?
BONDING
R E V I E W QUE ST I ONS Draw the complete orbital overlap for formamide (shown below). List all the bonds and draw any contributing resonance structures
BONDING
R E V I E W QUE ST I ONS
Which compound has the longest C-Br bond? Which compound has the shortest C-Br bond?
Draw all contributing resonance structures for the following compounds
BONDING
R E V I E W QUE ST I ONS Riboflavin, or vitamin B2, is shown below. What are the approximate bond angles at the labelled atoms
1:_____ 2:_____ 3:_____
4:_____ 5:_____ 6:_____
