Organic Chemistry Exam 4

radical reactions involve what kind of bond cleavage

homolytic

what is the stereochemistry of radical reactions

mixed

rule for radical stability

increasing substitution increases stability

molecule that forms more stable radical has (__) BDE for C-H bond

lower

rank in order of increasing radical stability:

allylic

primary

benzylic

tertiary

secondary

methyl

methyl, primary, secondary, tertiary, allylic, benzylic

t or f: resonance with radicals can only be done with adjacent double bond

t

detail the 3 steps of radical mechanism and the possible patterns in each step

1. initiation: homolytic cleavage

2. propagation: addition to pi bond, hydrogen or halogen abstraction, elimination

3. termination: coupling

what is homolytic cleavage

going from nonradical to 2 radicals

what is coupling

going from 2 radicals to nonradical

what happens during propagation

go from radical and nonradical to other radical and nonradical

when must ALL PRODUCTS BE MADE during radical mechanism

propagation

what is good at coupling

carbon

what does chlorination of methane require

light or heat

which termination products must we include

alkylation and the actual product and one other

a radical initiator possesses a (_) that cleaves (__) with (__) or (__)

weak bond / homolytically / heat / light

examples of radical initiators

dihalides, alkyl peroxides (RO-OR), and acyl peroxides

what radical initiator is must reactive and less heat is needed to break

acyl peroxides

explain thermodynamics of radical reactions

no change in entropy so delta G = delta H (H is enthalpy, describes stability of reactants, products, and intermediates)

answer with positive or negative: bonds broken is (__) and bonds formed is (__)

positive / negative

which halogen is most thermodynamically favorable and spontaneous for radical halogenation? how do we know?

fluorine / has most negative delta G

for chlorination, what does the transition state resemble and why?

reactants because both steps exothermic

for bromination, what does the transition state resemble

intermediate because first step endothermic but second and overall reaction exothermic

why does chlorination produce 60/40 while bromination produces 97/3

chlorination doesn’t have as much radical character because resembles reactants while bromination resembles a radical more and thus mostly favors more substituted

t or f: radical bromination always leads to most stable formed

t

do the transition states of hydrogen abstraction in chlorination or bromination have a greater difference in energy for primary, secondary, and tertiary radicals

bromination

what is used in allylic bromination

NBS

radical initiator of HBr addition to alkene

peroxide (ROOR)

is a hydrogen radical ever formed

not really

why is HBr addition to alkene anti mark

forms more stable radical

how to write polymers

bracket around monomer and then n is number of times they repeat

what to do when functional group moved

combination of addition and elimination

what is the only thing you can do with alkanes

radical bromination with NBS and light/heat

why are alkynes important

can do alkylation and then grow chain

what happened if we lost carbons

ozonolysis