Structure and Stereochemistry
Terrence P. Sherlock
Burlington County College
• Ionic bonding: electrons are transferred.
• Covalent bonding: electron pair is shared.
Chapter 1 2
• Bonding electrons
• Nonbonding electrons or lone pairs
Satisfy the octet rule! =>
Chapter 1 3
Chapter 1 4
• Amount of electrical charge x bond length.
• Charge separation shown by electrostatic
potential map (EPM).
• Red indicates a partially negative region and
blue indicates a partially positive region.
Chapter 1 5
Greater DEN means greater polarity
Chapter 1 6
Calculating Formal Charge
• For each atom in a valid Lewis
• Count the number of valence electrons
• Subtract all its nonbonding electrons
• Subtract half of its bonding electrons
Chapter 1 7
Chapter 1 8
• Only electrons can be moved (usually
lone pairs or pi electrons).
• Nuclei positions and bond angles
remain the same.
• The number of unpaired electrons
remains the same.
• Resonance causes a delocalization of
• The real structure is a resonance hybrid.
• All the bond lengths are the same.
• Each oxygen has a -1/3 electrical charge.
Chapter 1 10
Major Resonance Form
• has as many octets as possible.
• has as many bonds as possible.
• has the negative charge on the most
• has as little charge separation as
Chapter 1 11
not have octet.
Chapter 1 12
• Full structural formula
(no lone pairs shown)
• Line-angle formula
• Condensed structural
formula • CH3COOH
• Molecular formula • C 2H 4O 2
• Empirical formula • CH2O
Chapter 1 13
Arrhenius Acids and Bases
• Acids dissociate in water to give H3O+ ions.
• Bases dissociate in water to give OH- ions.
• Kw = [H3O+ ][OH- ] = 1.0 x 10-14 at 24°C
• pH = -log [H3O+ ]
• Strong acids and bases are 100%
Chapter 1 14
Acids and Bases
• Acids can donate a proton.
• Bases can accept a proton.
• Conjugate acid-base pairs.
acid base conjugate conjugate
Chapter 1 15
Acid and Base Strength
• Acid dissociation constant, Ka
• Base dissociation constant, Kb
• For conjugate pairs, (Ka)(Kb) = Kw
• Spontaneous acid-base reactions
proceed from stronger to weaker.
pKa 4.74 pKb 3.36 pKb 9.26 pKa 10.64
Chapter 1 16
Determining Relative Acidity
• Resonance stabilization of conjugate
Chapter 1 17
As the bond to H becomes more
polarized, H becomes more positive
and the bond is easier to break.
Chapter 1 18
• As size increases, the H is more loosely
held and the bond is easier to break.
• A larger size also stabilizes the anion.
Chapter 1 19
• 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
Chapter 1 20
Lewis Acids and Bases
• Acids accept electron pairs = electrophile
• Bases donate electron pairs = nucleophile
Chapter 1 21
POWER POINT IMAGES FROM
“ORGANIC CHEMISTRY, 5TH EDITION”
ALL MATERIALS USED WITH PERMISSION OF AUTHOR
PRESENTATION ADAPTED FOR BURLINGTON COUNTY COLLEGE
ORGANIC CHEMISTRY COURSE
ANNALICIA POEHLER STEFANIE LAYMAN CALY MARTIN
Chapter 1 22