Chemical Reactions

Chemical reaction

transformation of a substance into another substance through changes in chemical bonds

for a reaction to occur, molecules must overcome

electron/electron repulsion to approach each other

How to overcome electron/electron repulsion

charge attraction and orbital overlap

delta G

change in Gibbs free energy

delta g less than 0

spontaneous

spontaneous

products lower in energy than reactants

delta g over 0

not spontaneous

not spontaneous

reactants lower in energy than products

delta H

change in enthalpy

Negative delta H

exothermic

exothermic

release heat

positive delta H

endothermic

Endothermic

absorbs heat

Endothermic or exothermic favored

exothermic

Spontaneous goes with

exothermic!

Not spontaneous goes with

endothermic!

T delta S

change in entropy

Reaction coordinate diagram

illustrates energy changes over course of reaction, from starting materials to products

transition state

maximum energy in reaction, the point at which the bond is broken or formed

mechanism

the precise sequence of bond making and breaking steps from reactant to products

Bronstead Lowry

base is proton acceptor and acid is proton donor

Lewis

base is electron pair donor and and acid is electron pair acceptor

electrophile

electron loving, molecule that accepts a pair of electrons in a mechanistic step

electrophile characteristics

neutral to positively charged electron deficient, react from empty acceptor orbitals

electrophile examples

positive charge for empty orbital, double bonds to highly En atoms, single bongs to highly En atoms

nucleophiles

nucleus loving, molecule that donates electron pair in a mechanic step

nucleophile characteristics

neutral to negatively charged, good donor orbitals

nucleophile examples

lone pairs, negative charge, pi bonds between not so en atoms, single bonds to electropositive atoms