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Bond lengths from shortest to longest
Triple, double, single
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Bond strengths from weakest to strongest
C-C, C=C, C=C
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Bond stability from least stable to most
Triple, double, single.
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Calculating formal charge
Formal charge = valence – assigned
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Energy changes in forming and breaking bonds
Energy is always released when a bond is formed, and required when a bond is broken.
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Heat of combustion trend
The less stable the bond, the greater will be the heat of combustion. The more stable the bond, the lower the heat of combustion.
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Hückel's Rule
To determine aromaticity,
4n + 2 pi
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sp2 geometry
Trigonal planar or bent
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sp3 geometry
Tetrahedral or trigonal pyramidal
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sp3d geometry
Trigonal bipyramidal
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sp3d2 geometry
Octahedral or square pyramidal
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Conformational isomers
Same exact compound arranged in different spatial orientations.
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Structural isomers
Same molecular formula, different bond to bond connectivity.
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Stereoisomers
Same formula, same bond to bond connectivity, different in the 3-D arrangement.
- Enantiomers: non-identical, mirror images.
- Diasteromers: non-identical, and NOT mirror images.
- (+ or d) - rotates light clockwise, dextrorotatory
- (– or l) - rotates light counterclockwise, levorotatory
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Meso compounds
Two or more chiral centers that contain a plane of symmetry.
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sp3d bond angle
90˚/120˚ or 180˚
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