chapter 4 Flashcards
thermodynamics
deals with energy changes accompanying chemical and physical transformations
- describes properties of systems at equilibrium
kinetics
variation of reaction rates with different condition and concentrations of reagents
- rates: how fast something happens
3 steps of chain reaction mechanism
- initiation
- propagation
- termination
initiation
generates reactive intermediate
propagation
reactive intermediate reacts with stable molecule to form product and another reactive intermediate
termination
reactive intermediates destroyed
what kind of light is used to split Cl2
blue light (hv)
reactive intermediate
short-lived series never present in high concentration because it reacts as quickly as it is formed
free radicals
species with unpaired electrons
stability of free radicals
methyl < primary < secondary < tertiary < allylic/benzylic
stability of free radicals according to hybridization
sp < sp2 < sp3
if Keq is larger than 1…
then reaction is favored from left to right
if Keq is less than 1
reaction is favored from right to left
Gibbs free energy (delta G)
change in free energy:
(free energy of products) - (free energy of reactants)
delta H (enthalpy)
(enthalpy of products) - (enthalpy of reactants)
delta G in relation to H,T,S
delta G = delta H - T(delta S)
delta S (entropy)
(entropy of products) - (entropy of reactants)
reactions tend to favor products with the ________ enthalpy
lowest
change in enthalpy (heat of reaction)
amount of heat evolved or consumed in the course of a reaction
do exergonic reactions have a negative or positive g
negative
do endergonic reactions have a negative or positive g
positive
if weaker bonds are broken and stronger bonds are formed, it is an ____________ reaction
exothermic
if stronger bonds are broken and weaker bonds are formed, it is an ____________ reaction
endothermic
entropy
measure of randomness, disorder, or freedom of motion
reactions favor products with the _________ entropy
greatest
bond-dissociation enthalpy (BDE)
amount of enthalpy required to break a particular bond homolytically
homolytic cleavage
each bonded atom retains one of bond’s two electrons - free radicals result
heterolytic cleavage
one of the atoms retains both electrons - ions results