Orgo 1 Exam 4

classification of haloalkanes

methyl < primary < secondary < tertiary < allylic < benzyllic

Chlorination

unselective, all products form

Bromination

very selective, only major products form

Substitution

LG replaced with nucleophile

Elimination

kick out LG, form pi bond

1

weak nucleophile, needs a carbocation

2

strong nucleophile, will attack right away

Comparing LGs

less electronegative and larger atoms make better LG

Hoffman Product

less stable product

Zaitsev Product

more stable product

Small Strong Nucleophile

Zaitsev

Big Bulky Base

Hoffman

Rate of Dehydration

primary < secondary < tertiary

Br₂ / light

add Br to most substituted position

Cl₂ / light

add Cl to every possible radical position

initiation

no radicals → radicals

propagation

radicals → radicals

termination

radicals → no radicals

NBS + heat

add radical next door to alkene, resonate, add Br

HBr + ROOR + heat

add Br on less substituted side

S_N2

nucleophile attacks base of LG, LG leaves, nucleophile is added flipped stereochem

S_N1

LG leaves, C⁺ forms, shift/resonate, add nucleophile, deprotonate nucleophile

E₁

LG leaves, C⁺ forms, shift/resonate, nucleophile grabs H, C=C bond forms

E₂

nucleophile grabs H, C=C bond forms, LG leaves

HBr/Cl/I + primary alcohol

S_N2 replace OH with Br

HBr/Cl/I + tertiary alcohol

S_N1 replace OH with Br

HBr/Cl/I + primary alcohol w/ branching

S_N1 w/ rearrangment

PBr₃

replaces OH with Br stereochem flips

SOCl₂ and pyridine

replaces OH with Cl stereochem flips

TsCl and pyridine

replaces OH with OTs sterochem stays same

H₂SO_{4 (cat)} and heat

PLSRD

PCC + primary alcohol

aldehyde

PCC + secondary alcohol

ketone

PCC + tertiary alcohol

nothing

H₂CrO₄/Jone’s Reagent + primary alcohol

carboxylic acid

H₂CrO₄/Jone’s Reagent + secondary alcohol

ketone

H₂CrO₄/Jone’s Reagent + tertiary alcohol

nothing

HIO₄

chop between cis OHs → aldehyde or ketone

NaBH₄ / CH₃OH

reduce aldehydes and ketones to OH