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Chemical Kinetics
- The velocity or rate at which the concentrations of reactants and products change
- Speed at which a reaction goes to completion
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Chemical Thermodynamics
- Changes in energy that take place when processes like chemical reactions occur
- Controls the extent to which a reaction goes to completion
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Thermodynamic Control
- A transformation that yields the most stable products.
- Outcome determined by the net favorable change in energy in going from starting materials to products
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Kinetic Control
A reaction in which the product obtained is the one formed fastest; may not be thermodynamically the most stable
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Gibbs Standard Free Energy hange
ΔG° = ΔH° - TΔS°
ΔG°: Release of energy
ΔH°: Enthalpy
T: Temperature in kelvin
ΔS°: Entropy
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ΔS°: Entropy
Increasing disorder correlates with an increase in the value of S
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ΔH°: Enthalpy
Heat absorbed or released at constant pressure during the course of the reaction.
ΔH = (energy of bonds broken) - (energy of bonds formed)
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Endothermic
Heat-absorbing
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Exothermic
Heat-releasing
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Reaction Coordinate Diagram
- Describes the rxn progress over time
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Driving Force
Large value for K indicates that a reaction goes to completion
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Transition State
Maximum energy
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Activation Energy
Energy required to raise the energy of the starting compounds to the transition state
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Rate Constant
Proportionality constant; K
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First Order
Rate depends on the concentration of only one reactant i.e A -> B
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Second Order
Rate depends on the concentrations of two molecules
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Rate Determining Step (RDS)
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Bronsted Acid
Proton Donor
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Bronsted Base
Proton Acceptor
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Ka
Acid dissociation constant
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pka
pka= -log(ka)
Smaller pka=stronger acid=more stable CB
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Common Acids
HCl, HBr, HI, H2SO4, H3PO4, HNO3, H30+
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Common Bases
LiOH, KOH, NaOH, NaOCH3, Lone Pair on Atom
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Factors that determine acidity
- 1) Electronegativity
- 2) Size
- 3) Resonance
- 4) Hybridization: more s character=more stable
- 5) Induction: stabilization through "sigma" bonds (dipole moments)
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Lewis ABC
Unfilled orbitals or partial charges
- Lewis Acid: electron acceptor
- Lewis Base: electron donor
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3 types of alkanes
- Straight Chain
- Branched
- Cycloalkanes
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Properties of alkanes
- They are unreactive and non-bolar.
- They use London dispersion forces (weak) and van der waals interactions (weak)
They rotate around sigma bonds
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Torsional Strain
Electron Repulsion in overlapping bonds
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Steric Hinderance
2 groups occupying the same space
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Gauche
Steric interaction of 2 groups 60° apart
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Anti-conformation
2 Largest substituents on each C are 180°
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Which hydrogens must be drawn in Newman projections?
The ones directly connected to the projection
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Totally eclipsed
When the two largest molecules are on top of each other
3 torsional strain and steric hinderance
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