RPA - Mechanisms Flashcards
Give the initiation step in FRS
Cl2 –> 2Cl.
Give the two propagation steps in FRS
CH4 + Cl. –> CH3. + HCl
CH3. + Cl2 –> CH3Cl + Cl.
Give the major termination step in FRS
CH3. + Cl. –> CH3Cl
Give the minor termination step
CH3. + CH3. –> C2H6
What is required to avoid further FRS involving CH3Cl and Cl.
Excess CH3 to reduce chance of encounter
What is required to start the Cl bond fission?
UV light
What type of bond fission occurs when 2 Cl. formed?
Homolytic bond fission
For nucleophilic substitution, what are the conditions?
Reflux, ethanol/water solvent, heat
Give the equation for the formation of the electrophile Br+
FeBr3 + Br2 –> FeBr4- + Br+
How can we describe FeBr3
Halogen carrier catalyst
What are the conditions for Electrophilic substitution using Br+?
Anhydrous, reflux, FeBr3 catalyst
Give the equation for the formation of FeBr3 after the substitution
FeBr4- + H+ –> FeBr3 + HBr
Give the overall reaction for the reaction between bromine and benzene
C6H6 + Br2 –> C6H5Br + HBr
Give the reagents in the nitration of benzene
CONC HNO3
CONC H2SO4
Give the conditions for nitration of benzene
Reflux
Give the equation for the production of NO2+ ion
HNO3 + H2SO4 –> NO2+ + HSO4- + H2O
Give the equation for the reformation of H2SO4 after the nitration
HSO4- +H+ –> H2SO4
In nucleophilic addition to carbonyls, what are the reagents/conditions?
NaBH4 - reducing agent
H2O/ethanol solvent
Gentle heating
What is the stoichiometric ratio of carbonyl to [H] in reduction of aldehydes/ketones?
1:2
Carbonyl:[H]
What is the reason for the temperature when nitrating benzene?
> 50 means multiple substitutions.
When writing out intermediate in electrophilic substitution, what is the shape of the benzene?
‘Smiley Face’ in the ring, as the pi system is incomplete. Remember + in the centre
What reactions involve nucleophilic addition?
reduction of carbonyls to alcohols
Why are both ethanol and water used for nucleophilic addition reactions?
everything dissolves in the combined solvent
What is the full two step reaction for the production of NO2+ ion in nitration of benzene?
H2SO4 + HNO3 –> H2NO3+ + HSO4-
H2NO3+ –> NO2+ + H2O
H2SO4 is stronger acid, so protonates the HNO3
