CHY 142 Lecture Notes - Lecture 1: Boiling Point, Hydrogen Bond, Molecular Mass
28 Dec 2015
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Electronics- bonding arrangements and presence of functional groups. Bond forming rxns: slower, require precise orientation. Stronger intermolecular attractions (dipole-dipole forces, hydrogen bonding) increase boiling point. Lone pairs and formal charges: formal charges: appear when atoms do not exhibit the appropriate # of valance electrons. Rules: 1) only lone pairs (charges) and pi bonds can move (not sigma bonds: each structure must have the same # of electrons and same overall charge. Stable resonance structures: more stable resonance structures have: octet rule satisfied for all atoms. ******never exceed valance for a 2nd row element* Charges can always be stabilized by resonance. Positive charges stabilized by less electronegative atoms. Acidity is based on stability of the conjugate base: Electronegativity increases with increasing s" character of an atom. (why alynes are more acidic than alkanes) Inductive stability increases with electronegativity of an ionic atom (why alcohols are more stable than amines) Anions can be stabilized through resonance (why carboxylic acids are the strongest)
