Ch. 16 - Ethers, Epoxides, And Sulfides

Front 1

What are crown ethers used for?

Back 1

1. They are used as solvents.

2. They solvate positive cations, allowing nucleophilic anions to attack electrophilic carbons via Sn2 pathway

Front 2

PROPERTIES/PRODUCT/SOLVENT OF:

Williamson Synthesis

Back 2

Reaction of 1* Alkyl Halide and an Alkoxide

Product: Ether

Solvent: DMSO

Front 3

PROPERTIES/REAGENT/PRODUCT OF:

Acid-catalyzed addition of alcohols to alkenes

Back 3

'Mark' addition

Acid (H+) is the only reagent

Product: Ether

Front 4

PROPERTIES/SUBSTRATE/REAGENTS/ OF:

Haloetherification

Back 4

Addition reaction
1) Halogen X is added to less substituted side, leaving X- behind
2) Resulting carbocation is attacked by nucleophilic Oxygen of the alcohol

Substrate: Alkene with vinylic H on each side of double bond

Reagents: X2 and ROH
Product: Vicinal Haloether

Front 5

PROPERTIES/PRODUCT/REAGENTS OF:

Oxymercuration - Demurcuration of alkenes

Back 5

Analogous to hydration but use an R-OH instead of water.
Product: Ether

Reagents:
1. Hg(OAc)2 , R-OH
2. NaBH4 , -OH

Front 6

PROPERTIES/SUBSTRATE/REAGENTS OF:

Intramolecular William Synthesis

Back 6

-OH removes proton, RO- attacks vicinal carbon, halogen gets booted

Substrate: vicinal halohydrin

Reagent: NaOH

Front 7

SUBSTRATE/REAGENT/PRODUCT OF:

Condensation of Alcohols

Back 7

Substrate: 1* Alcohol - 2 equivalents

Reagent: H2SO4

Product is always a symmetrical ether

Front 8

SUBSTRATE/REAGENT/STEPS/PRODUCTS OF:

Acid-catalyzed cleavage of ethers

Back 8

Substrate: Ether

Reagent: HX (HCl, HBr)

Rxn is two steps:
1: Forms an alcohol and an alkyl halide
ROR' + HX ----> RX + R'OH
2. The alcohol formed in step 1 reacts with a 2nd HX (dehydration), forming another alkyl halide and a water.
R'OH + HX ----> R'X + H2O

Final Products: 2 Alkyl Halides, 1 Water

Front 9

PROPERTIES/PRODUCTS OF:

Acid-catalyzed cleavage of cyclic ethers

Back 9

Same pathway as non-cyclic ethers (Protonation, Halide ion attacks ring, ring opens)

Initial Product: carbon chain with halide at one end and alcohol at other

Final Product: the alcohol portion undergoes a dehydration, so final product is a terminal di-halide X-R-X

Front 10

SUBSTRATE/REAGENTS/STEPS OF:

Formation of vicinal halohydrin

Back 10

Substrate: Alkene

Reagents: X2 , H2O

Steps:
1) X attaches to both sides (forming a halonium ion complex)
2) H2O attacks more substituted side and breaks one of the two halide bonds
3) Proton dissociates from H2O

Front 11

SUBSTRATE/REAGENT/STEPS OF:

Conversion of vicinal halohydrins to epoxides

Back 11

Substrate: Vicinal Halohydrin

Reagent: NaOH ( good base, bad -:Nu)

Steps:
1) Base removes proton from alcohol group
2) Resulting O- attacks vicinal carbon
3) Vicinal halogen gets booted

Front 12

PROPERTIES OF:

Nucleophilic Ring Opening of Epoxides

Back 12

1. Sn2-type reaction

2. Inversion at the attacked carbon

3. Less crowded C is attacked

Front 13

REAGENT/SOLVENT OF:

Nucleophilic Ring Opening of Epoxides

Back 13

Reagent: Nucleophiles (Alkoxides, Alkanethiolates, Grignards + acid)

Solvent: Protic Solvents such as Alcohol or H2O, Ether for grignards

Front 14

REAGENT/SOLVENT/PROPERTIES

How do you form a trans-diol from an epoxide?

Back 14

Reagent: NaOH

Solvent: Ethanol or H2O

Nucleophilic ring openeing
-OH attacks, and the resulting O- of the epoxide is protonated.

Front 15

What is unique about Ring Opening of Epoxides using LiAlH4?

What reagents do you need?

Back 15

Same as other nucleophilic ring opening reactions, but H- attacks as a nucleophile

Reagents:
1. LiAlH4
2. H2O

Front 16

STEPS/REAGENTS OF:

Acid Catalyzed Ring Opening of Epoxides

Back 16

1. Acid protonates the oxygen
2. Nucleophile attacks MORE substituted C
3. Inversion at site of attack

Possible Reagents:
1. R-OH with H2SO4
or
2. H-X

Front 17

How can you form a vicinal di-halide using acid-catalyzed ring opening of epoxides?

Back 17

Run a standard H-X acid-catalyzed ring opening of an epoxide, but at higher temps.

Instead of: R--XC--COH--R
You'll get: R--XC--CX--R

Front 18

REAGENTS FOR:

Formation of Alkanethiolate from an Alkyl Halide.
RX ----> RS-

Back 18

Reagents:
1. Thiourea
2. NaOH, H2O

Front 19

PROPERTIES/REAGENTS/SOLVENT OF:

Preparation of Sulfides R-S-R'

Back 19

Formed using basic substitution reaction.

Reagents: Alkanethiolate and a 1* or 2* Alkyl Halide

Solvent: Alcohol or H2O

Front 20

What setup can be used to convert a Thiol into a Sulfide?

Back 20

1. NaOH
2. 1* or 2* alkyl halide
RSH ---------------> RSR'
(alcohol solvent)

Front 21

What 3 reagents will oxidize sulfides into sulfoxides?

Back 21

NaIO4 - Sodium Metaperiodate
H2O2 (1 Equivalent)
Peroxy Acid (1 Equivalent)

Front 22

What two reagents will oxidize sulfides into sulfones?

Back 22

H2O2 (2 Equivalents)
Peroxy Acid (2 Equivalents)

Front 23

PROPERTIES/PRODUCT OF:

Alkylation of Sulfides: Sulfonium Salts

Back 23

Sulfides can act as nucleophiles and attack alkyl halides

RSR' + R"X ----> RSR'-R" + X

Product will have 3 total R-groups and a positive charge on sulfur.

Front 24

PROPERTIES/SUBSTRATE/REAGENT/PRODUCT OF:

Peroxy acid oxidation of alkenes

Back 24

Syn Addition
No Inversion

Substrate: Alkene

Reagent: Peroxy acid
(ie - peroxyacetic acid CH3COOOH)

Product: Epoxide

Front 25

PROPERTIES/SUBSTRATE/REAGENTS OF:

Sharpless epoxidation

Back 25

1* or 2* Allylic alcohols are converted to epoxides by oxidation

Substrate: allylic alcohol

Reagents:
1. tert-butyl hydroperoxide
(CH3)3COOH
2. Titanium Isopropoxide (cat.)
Ti[OCH(CH3)2]4
3. diethyl tartrate (cat.)