Electronic Structure and Bonding. Acids and Bases Chapter 1

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Electronic Structure and Bonding. Acids and
BasesChapter 1

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Contents of Chapter 1

• Bonding, Lewis Structures
• Atomic Molecular Orbitals
• Hybrid Orbitals
• Single Bonds
• Multiple Bonds
• Dipole Moments Polar Bonds
• Acid/base Theory

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Ionic Bonds
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Covalent Bonds
covalent bond
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Polar Covalent Bonds
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Polar Covalent Bonds

• There is a continuum of bonding types

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Electronegativity
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Lewis Structures

• The chemical symbols we have been using in which
  valence electrons are shown as dots are called
  Lewis structures

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Drawing Lewis Structures

• Write the symbols for the elements in the correct
  structural order
• Consider nitric acid, HNO3

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Sticks and Eyeballs

• Bonds Lone Pairs 4 (Octet Rule)
• Exceptions H has 1 bond, B has 3 bonds
• Bonds Count spaces from noble gas
• Convert bond to LP is (-), LP to bond is ()
• Exceptions C(), B(-)

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Formal Charges

• Subtract the number of assigned electrons from
  the number of valence electrons for an uncombined
  atom of the same element

6 - 6 0
1 - 1 0
6 - 7 -1
5 - 4 1
6 - 6 0
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Condensed Structural Formulas

• Kekulé formulas also are called structural
  formulas
• Often, structural formulas are condensed

becomes
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1s and 2s Orbitals
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2p Orbitals
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Molecular Orbital From p Electrons

• Molecular orbitals also can be formed from p
  orbitals

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Hybrid Orbitals

• Methane, CH4, has four equivalent carbon-hydrogen
  bonds

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Hybridization

• Theory Mix the 2s orbital with the three 2p
  orbitals to form four equivalent hybrid orbitals

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Hybridization - Tetrahedral Carbon

• The sp3 hybrid orbital on carbon also can bond
  with another sp3 hybrid orbital from a
  neighboring carbon to form a carbon-carbon single
  bond

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sp2 Hybridization in Ethene

• The carbon-carbon bond formed from the overlap of
  an sp2 orbital on one carbon with an sp2 orbital
  on a neighboring carbon atom results in an
  orbital which is cylindrically symmetric about
  the carbon-carbon axis

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sp2 Hybridization in Ethene

• A second bond is formed between the two carbon
  atoms via the side-by-side overlap of the
  remaining (un-hybridized) p orbitals
• Electron density accumulates above and below the
  carbon-carbon axis

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sp Hybridization in Ethyne

• The overlap of the sp hybrid orbitals forms a ?
  bond

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sp Hybridization in Ethyne

• The remaining p orbitals overlap side-by-side,
  forming ? bonds with electron density above and
  below the carbon-carbon axis as well as in front
  and in back

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Summary of Orbital Hybridization
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Curved Arrows

• Curved arrows represent motions of PAIRS of
  electrons
• Tail of arrows is ORIGINAL location of electrons
• Point of arrow is FINAL location of electrons

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Acids and Bases in Organic Reactions

• Hs in organic compounds have varying degrees of
  acidity

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Acidity and Structure

• Electronegative atoms or groups increase acidity

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pKa as a Stability Parameter
pKa?DGº

• pKa tracks relative potential E of conj base
• Strong acids low pKa stable conj base
• Weak acids high pKa unstable conj base

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Examples of Organic Acid - Base Reactions

• To use pKa as a PE write it under base form
• Rxn shifts to side with lowest PE
• Textbook shows pKa values under acids

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Relative Amounts of Different Forms of a Compound