Structure 2.3

• Evidence for Benzene's resonance structure


  The length of all their bonds is between that of single and double bonds and they are formed at a 120 degree angle

  Benzene's energy is released by stable amounts explained by Pauling's: delocalized electrons prevent full double bonds that need to absorb H2 to break and release energy

  Addition reactions which were favorable to double bonds was energetically unfavorable for Benzene- it turns orange in Br2 solutions like single bonds
• Double/triple bond model of Benzene


  August Kekulé
• Hybrid resonance structure on Benzene 


  Linus Pauling
• Resonance structures

  Visual representations of delocalized electrons being shared between elements in a bond through overlapping p-orbitals; increasing conductivity and reactivity and making the bonds easy to break
• Polar covalent compounds


  Have an electronegativity between 0.4 to 1.8. When drawn, they have an asymmetrical pull of electrons or a symmetrical structure with different elements on either end

  
• Non polar covalent compounds


  Symmetrical with same elements on the same axis. Electronegativity between 0 and 0.4
• Ionic compounds

  Electronegativity above 1.8
• Polarity is the asymmetrical pull of electrons
• Sigma bonds

  Axial overlaps between two s-orbitals, two p-orbitals or 1 s and 1 p orbital. 1 sigma bond present in each bond type (single, double, triple)

  
• Pi bonds

  sideways overlap of p orbitals. 1 pi bond present in double bonds, 2 pi bonds present in triple bond

  
• Low solubility

  Large molecules with only part of the molecule being polar causes only that part to dissolve in polar solvents and vise versa
• Intermolecular forces

  Physical changes, bonds between different molecules
• London Dispersion forces


  Present in all elements, more present in heavier elements/further down the periodic table, weakest intermolecular force, very non-polar.
• Dipole-dipole bonding

  Only found in polar molecules, more polar=stronger force, overall 2nd most weak Intermolecular force
• Hydrogen Bonding

  Between Hydrogen and either Oxygen, Nitrogen, or Fluorine, strongest Intermolecular force, it can also be an intramolecular force
• Intramolecular forces


  Much stronger than Intermolecular forces, within 1 molecule
• Hydrogen Bonding (intra)

  When its close enough together, a O, N, or F can be attracted to a H in the same molecule and form a intramolecular hydrogen bond, though slightly weak
• coefficient in hybridization

  signifies energy levels - s can exist on all levels, p can exist is levels 2 and up and d can exist in levels 3 and up
• Exponents in hybridization

  Show how many electrons are filled in each orbital
• Lattice distortion 


  Happens when elements of different atomic radii combine in bonding which can hinder movement and increase boiling point because they are so hard to nudge out of position
• Dipole induced dipole

  Intramolecular force that is caused by the presence of a very polar molecule making a non-polar molecule temporarily create internal dipoles. Larger molecules with their electrons further from the nucleus are easier to persuade and influence with polar presence than smaller molecules.
• Ionic bonding

  Intramolecular force between two oppositely charged ions or with different electronegativities
• Covalent bonding

  Intramolecular force of sharing electrons by balancing repulsive and attractive forces between the elements