Chapter 18: Ethers + Epoxides, Thiols + Sulfides

ether

R-O-R

epoxide

thiol

R-SH

sulfide

R-S-R

ether nomenclature

groups attached to oxygen + ether

• alkoxy substituent

ether properties

• C-O-C bond is almost tetrahedral (112 degrees)

• sp3 carbon

• C-O has slight dipole movement

• lower boiling points than alcohols, higher boiling points than hydrocarbons

william ether synthesis

• less subsituted is better alkyl halide

• more substituted + more hindered is better alkoixde ion

• not 3 alcohols

williamson ether vs alkoxymercuration

WE

• less bulky

akoxy

• bulky

• needs to be able to form C=C from ether

benzylic

allyl

vinyl

epoxide

3-membered cyclic ethers

• always named as substituents - “epoxy”

reaction of alkenes w/mCPBA

reactivity of alkene increases w/increasing alkyl substitution

• 1 equiv = only 1 C=C reacts

ring opening under acidic conditions

1 + 2 substitution: nucleophile attack occurs primarily at the less substituted site

3: nucleophile attack occurs at the more highly substituted site

both products form

• nucleophile (Br) and OH are trans

• Br is at more hindered site

• inversion occurs

ring opening under basic conditions

Sn2, reaction occurs at less highly substituted position

• inversion of stereo!

NMR

epoxides have a slightly higher field (more right) than ethers due to ring strain

thiol

R-SH

thiol nomenclature

add thiol to name of parent hydrocarbon

• substituent is mercapto

sulfides nomenclature

R-S-R

• sulfide is ending

• subsistent is alkylthio