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Unformatted text preview: 9/12/2011 Which anion is more stable, A or B? Why? Why do ethane and ethyne have very different pKas?
pKa Ka 25 10-25 pKa
A ethyne 50 50 10-50 ethane B What hybrid orbitals are used to form the C-H bond in
ethane, A. sp B. sp2 C. sp3? Are the electrons of the anion more stable in an sp
A. Yes B. No pKa pKa 25 25 ethyne sp
sp3 ethane hybrid
(sp3) trigonal planar
(sp2) Which compound has the strongest C-H bond
B. ethane? success!
pKa sp s p sp3 25
ethyne sp3 50 For larger molecules
there is a lot of success
but we are still working
on the problem. from the application of quantum
mechanics to H· we can derive all
of the atomic orbitals as well as
their hybrids. 1.
1. molecular orbital
2. valence bond theory
(resonance structures) H· ethane quantum
s py for all atoms but H pz
energy 1 9/12/2011 For a C=C bond choose the π-antibonding molecular orbital
from the following list. resonance (Lewis)
structures • valence bond theory
H1s (A) C C σ-antibonding molecular orbital (B) • molecular orbital theory C C σ-bonding molecular orbital H1s (C)
H Why is the bonding orbital
more stable? CC π-antibonding molecular orbital H • molecular orbital theory What
What role do antibonding
orbitals play in your life? H H C H1s H1s bonding
MO a molecular orbital theory Photochemistry! antibonding
Energy π-bonding molecular orbital (D) Orbital
Energy CC H Orbital
Energy H • molecular orbital theory
C C2p C C C C C2p C Can there be health problems associated with light? antibonding C DNA
C C Csp2 Csp2 Orbital
Energy C C bonding http://en.wikipedia.org/wiki/Pyrimidine_dimers 2 9/12/2011 What role does light play
in your life? molecular orbital theory Choose the best Lewis (resonance)
structure for formamide.
O C C antibonding H C N H H formamide color C C H C N C I 3. add formal charges BH C H C Br 2. maximize bonding O
H Si P S Cl 1. add electrons O A 34567 B C NOF N H C O
C H H H O DH N C N H H H bonding vision molecular orbital theory C C Choose the best Lewis (resonance)
structure for formamide. antibonding battery solar energy conversion C C O A H C O
N H BH C H C C N H C O
C H H H O DH N C N H H H bonding vision molecular orbital theory Choose the structure that is not a
resonance structure of formamide.
O C C antibonding H C N Resonance structures are different
electronic configurations of the
same structure. H H formamide C C O A H C O
N H BH C H C C bonding C C H H H
H C H O DH N C N H H H O O
N C H O
H N H O N
H H H C N H H 3 9/12/2011 Choose the order that has the following structures arranged
with respect to increasing stability. A 1 D 2 2 3 B 1 1 E 3 increasing
stability 3 stability 1 2 2 F 3 stability H
H H C 2 3 1 2 increasing
stability O O
N 1 increasing
stability 1 increasing O
C C stability increasing H 32 increasing N H H H C 3 N H H Arrange the following compounds in order of
1. maximum bonding (very important) 34567 B C NOF
Si P S Cl 2. minimize charge separation.
3. charges on electronegative atoms.
⊕ charges on electropositive atoms. Br
H C O O
H C H N H H C N H H H the complete story C O O O
H N H H a true but
story H C N H H a good story H C N H H an excellent story 4 ...
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