Polar Covalent Bonds; Acids and Bases

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Polar Covalent BondsAcids and Bases

• Bond Moments and Dipole Moments
• Formal Charge
• Resonance
• Bronsted-Lowry Acid/Base
• Lewis Acid/Base

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Pauling Electronegativity Scale
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Electronegativity Trends Ability to Attract the
Electrons in a Covalent Bond
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Electrostatic Potential Map Cholormethane
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Opposite polarity in CH3Li
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Methanol
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Dipole Moment (m) is sum of the Bond Moments
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Nonpolar CompoundsBond Moments Cancel Out
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NCl3 and BCl3
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Nitromethane
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Nitromethane has 2 Formal Charges
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Bonding Pattens for C, N, and O
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Common Cationic, Neutral and Anionic Forms
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Both Resonance Structures Contribute to the
Actual Structure
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Dipole Moment reflects Both Resonance Structures
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Curved Arrow Formalism Shows flow of electrons
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Resonance Rules

• Cannot break single (sigma) bonds
• Only electrons move, not atoms
• 3 possibilities
• Lone pair of e- to adjacent bond position
• Forms p bond
• - p bond to adjacent atom
• - p bond to adjacent bond position

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Resonance Stabilization of IonsPos. charge is
delocalized
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Two Nonequivalent Resonance Structures in
Formaldehyde
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Resonance in Acetate Anion
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Resonance in CH2NH2
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Definitions of Acids/Bases
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Dissociation in H2OArrhenius Acid forms
H3OBronsted-Lowry Acid donates a H
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Resonance Stabilization
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Measuring Acid StrengthKa
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Acid Strength defined by pKa
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Stronger Acid Controls Equilibrium
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Reaction Described with Arrows
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Equilibrium Reactions
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Acids Can React with Water
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The Effect of Resonance on pKa
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Identify the Acid and Base
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Equilibrium Favors Reactants
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Draw the Conjugate Acid and Base
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Propanol is a Base
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Draw the Conjugate Acid and Base
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Propanol is an Acid
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Some Acid-Base Reactions
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Carboxylic Acids can be Separated from non-acidic
Compounds
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Lewis Acids and Bases
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Lewis Acid and Base Reactions
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Lewis Base NucleophileLewis Acid Electrophile
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Draw the Acid-Base Complexes