Organic Chemistry Ch 13

ethers

ethers common name

name each r group invidually, put alphabetically, add ‘ether’ at end

ethers IUPAC name

large r group is parent group ending with ‘ane’, other r group named with -oxy at end

important ether properties

low boiling point (no hydrogen bonding within ether molecule)

fairly unreactive

oxygen is sp3 hybridized

naming crown ethers

number total atoms - crown - number oxygen atoms

Li crown ether

12-crown-4

Na crown ether

15-crown-5

K crown ether

18-crown-6

polyethers

antibiotics that behave similarly to crown ethers by holding metal cations, AKA ionophores

crown ethers used for substitution rxn what it looks like

crown ethers substitution reaction reagents

XF, benzene & crown ether that correlates to ‘X’

3 methods of preparing ethers

acid-catalyzed dehydration of ethanol

williamson ether reaction

alkoxymercuration-demercuration

acid catalyzed dehydration of ethanol what it looks like

acid catalyzed dehydration of ethanol reagents

hydrogen, more ethanol (starting material), heat

acid catalyzed dehydration of ethanol product

diethyl ether, other symmetric/simple ethers

williamson ether reaction what it looks like

williamson ether reaction reagents

1) NaH

2) RX

williamson ether reaction starting material & ending product

start with R-OH

end with asymmetric ether R-O-R’

when does williamson ether reaction occur

with primary unhindered alkyl halides as R-X

if pathway needs R-X to be secondary or tertiary, a different pathway will be used

alkoxymercuration-demercuration what it looks like

alkoxymercuration-demercuration reagents

1) Hg(OAc)2, ROH

2) NaBH4

alkoxymercuration-demercuration starting material & product

start with alkene

end with markovnikov addition of RO & H, alkoxy group goes on more substituted carbon

2 reactions of ethers

acid cleavage

autooxidation

acid cleavage of ethers what it looks like

acid cleavage of ethers reagents

HBr or HI

acid cleavage of ethers how many substitutions

two (end with 2 alkyl halides) unless R group is aryl or vinyl, then only one (end with alcohol and alkyl halide)

autooxidation of ethers what it looks like

autooxidation of ethers reagents

O2

starting materials and products of autooxidation of ethers

start with ethers, end with hydroperoxides (explosive)

radical mechanism of autooxidation of ethers

oxirane

oxetane

oxolane

oxane

epoxides’ number of r groups

up to 4; more r groups is more reactive (more ring strain)

one way to name epoxides (O as side group)

treat oxygen as a side group

end with -epoxy after parent chain (oxane, etc)

put C numbers of 2 carbons connected to oxygen before parent chain name

one way to name epoxides (epoxide as parent chain)

oxirane, etc used as parent chain

oxygen is numbered first, number to get side groups at lowest number

name side groups, put before parent chain alphabetically as usual

3 ways to prepare epoxides

using peroxy acid

using halohydrins

sharpless epoxidation

epoxidation with peroxy acid what it looks like

peroxyacetic acid structure

epoxidation with peroxy acid reagents

mCPBA or peroxyacetic acid

epoxidation with peroxy acid starting material and product

start with alkene

end with epoxide

epoxidation with halohydrins what it looks like

epoxidation with halohydrins reagents

1) Br2, H2O (alkene to halohydrin)

2) any strong base, like NaOH (halohydrin to epoxide)

epoxidation with halohydrins starting material and product

start with alkene, then create halohydrin (has OH and X attached), then product is epoxide

stereoselectivity of epoxidation using peroxy acid and halohydrins

forms a racemic mixture, is not enantioselective

sharpless epoxidation what it looks like

sharpless epoxidation reagents

(CH3)3COOH, Ti[OCH(CH3)2]4 & (+)-DET OR (-)-DET

enantioselectivity of sharpless epoxidation

(+)-DET used - epoxide oxygen/triangle will form above plane

(-)-DET used - epoxide oxygen/triangle will form below plane

sharpless epoxidation starting material and product

start with alkene

end with epoxide, above or below plan depending on whether (+/-)-DET is used

epoxide reactions with strong nucleophiles what they look like

epoxide reactions with strong nucleophiles reagents

1) strong nucleophile

2) H2O

strong nucleophiles that often react with epoxides

RONa

NaCN

NaSH

RMgBr

LAH

stereochemistry of epoxide reactions with strong nucleophiles

basically SN2, nucleophile attacks less substituted carbon, stereochemistry inverts on attacked carbon

epoxide reactions with weak nucleophiles what it looks like

if primary/secondary Cs only

epoxide reactions with weak nucleophiles reagents

weak nucleophile

common weak nucleophiles reacting with epoxides

H2O, alcohols, HX

weak nucleophiles reacting with epoxides neutral nucleophiles (H2O, alcohols)

has an extra proton transfer

regioselectivity of weak nucleophiles reacting with epoxides

if primary or secondary carbon are only ones present, the nucleophile attacks the less substituted carbon - steric effect

I tertiary carbon is present, the nucleophile attacks there - electronic effect

less substituted carbon’s stereochemistry will invert, regardless of which carbon is attacked

acid-catalyzed dehydration of ethanol mechanism

Williamson ether synthesis mechanism

Alkoxymercuration-demercuration mechanism

Acid cleavage of ethers mechanism

preparing epoxide with peroxy acid mechanism

preparing epoxide from halohydrin mechanism

ether reactions with strong nucleophiles mechanism

ether reactions with weak nucleophiles mechanism

ether reactions with neutral nucleophiles (water, alcohol) mechanism

thiol

naming thiols

if -SH group, end name in -thiol

if -SH and -OH groups, end with -ol; -SH is mercaptan group, so name substituent mercapto-

reaction to form thiols

formation of thiols stereochemistry

SN2, inversion of stereochemistry, NaSH will form primary or secondary thiol

oxidation of thiol mechanism

reagents in oxidation of thiols

H2O, Br2

reagents in reduction of disulfide (back to thiol)

HCl, Zn

what reduction of disulfide looks like

sulfides

sulfur analogs of ethers

naming sulfides

same as for ethers, can be named as a substituent as a -thio group

preparation of sulfides what it looks like

preparation of sulfides reagents

NaOH, R2-X

preparation of sulfides mechanism

sulfoxide

sulfone

reagents for sulfide - sulfoxide

NaIO4

reagents for sulfide - sulfone

2 H2O2

Role of sulfides as reducing agents

Used in ozonolysis (DMS or DMSO alongside O3)

SN2 Substitution with Alkyl Halide Mechanism