Download Naming Ethers Naming Ethers

Naming Ethers
•  Common names are used frequently:
1.  Name each –R group.
2.  Arrange them alphabetically.
3.  End with the word “ether.”
Naming Ethers
•  IUPAC systematic names are often used as well:
1.  Make the larger of the –R groups the parent chain.
2.  Name the smaller of the –R groups as an alkoxy
substituent.
•  SEE: SKILLBUILDER 14.1.
Crown Ethers
K+
K+
K+
Question
•  Which reaction is the best candidate for catalysis by 18
-crown-6? (Which reaction proceeds faster in the presence of
the crown ether than in its absence?)
• 
• 
• 
• 
A)
B)
C)
D)
K+
Bromobutane + KCN (in toluene)
Phenol + Br2 (in water)
Butanol + H2CrO4 (in water)
CH3CH2CH2CHO + H2 (in ethanol)
Na+
Li+
Question
•  What is the name of the crown ether show at the right?
• 
A)
12-crown-4
• 
B)
10-crown-5
• 
C)
15-crown-5
• 
D)
18-crown-6
Question
•  Which crown ether would provide the fastest rate for the
following reaction?
• 
• 
• 
• 
A)
B)
C)
D)
12-crown-4
10-crown-5
15-crown-5
18-crown-6
Question
What is the product of the following reaction?
Question
What is the correct order of reagents needed for the
following transformation?
Mechanism
Question
•  Which of the following best represents the rate-determining
transition state for the reaction shown below?
•  A)
•  C)
B)
D)
Question
•  The most effective pair of reagents for the preparation of tert
-butyl ethyl ether is
• 
A)
potassium tert-butoxide and ethyl bromide.
• 
B)
potassium tert-butoxide and ethanol.
• 
C)
sodium ethoxide and tert-butyl bromide.
• 
D)
tert-butyl alcohol and ethyl bromide
Limitation
Preparation of Epoxides
w/ peroxyacids (MCPBA)
.
Question
Which of the following will produce the epoxide below?
Epoxidation Stereochemistry
•  Epoxidation forms a racemic mixture because
reaction occurs with equal probability on either face
of the double bond.
Enantioselective Epoxidation
•  The desired epoxide can be formed in excess by
choosing the appropriate catalyst. Note the position
of the –OH group.
•  SEE: CONCEPTUAL CHECKPOINT
14.16.
Enantioselective Epoxidation
•  In order to have an optically active product, one of
the reactants, or reagents, or catalyst in a reaction
must be chiral.
•  An example is a Sharpless catalyst, which forms
such a chiral complex that favors the formation of
one enantiomeric epoxide versus the other.
•  Catalyst:
Question
What is the product of the following reaction?
Question
True (A) / False (B)
Ring-opening of Epoxides
•  Epoxides can be opened by many strong
nucleophiles.
•  Both regioselectivity and stereoselectivity must be
considered.
Ring-opening of Epoxides
Question
• 
What is the product isolated when the epoxide below reacts
with NaOCH3 in CH3OH?
• 
A)
B)
• 
C)
D)
Question
•  What is the product of the reaction shown?
•  A)
B)
•  C)
D)
Question
What are the product(s) of the following reaction?
Acid-Catalyzed Ring-Opening
Reactions of Epoxides
Question
• 
What is the product isolated when the epoxide at the right
reacts with CH3OH and H2SO4?
• 
A)
• 
C)
B)
D)
Question
What is the product of the following reaction?
Thiols & Thio Ethers
Thiols
•  Sulfur appears just under oxygen on the periodic
table.
•  Sulfur appears in THIOLS as an –SH group
analogous to the –OH group in alcohols.
Thiols / Mercaptans
•  Thiols are also known as mercaptans.
•  The –SH group can also be named as part of a side
group rather than as part of the parent chain.
•  The mercaptan name comes from their ability to
complex mercury.
•  2,3-dimercapto-1-propanol is used to treat
mercury poisoning.
Thiols / Mercaptans
Thioethers / Sulfides
•  Thiols are known for their unpleasant odor.
•  Skunks use thiols as a defense mechanism: (E)-2butene-1-thiol, 3-methyl-1-butanethiol, and 2quinolinemethanethiol, and acetate thioesters of these.
•  Methanethiol is added to natural gas (methane) so that
gas leaks can be detected.
•  The hydrosulfide ion (HS–) is a strong nucleophile and
a weak base.
•  HS– promotes SN2 rather than E2.
•  Sulfur analogs of ethers are called SULFIDES or
THIOETHERS.
•  Sulfides can also be named as a side group.
Question
Thioethers / Sulfides
•  Sulfides are generally prepared by nucleophilic
attack of a thiolate on an alkyl halide.
Thioethers / Sulfides
Sulfide reactions:
What is the correct order of reagents needed for the
following transformation?
Thioethers / Sulfides
Sulfide reactions:
Nucleophilic substitution of an alkyl halide:
Nucleophilic substitution of an alkyl halide:
The process produces a strong alkylating reagent that can
add an methyl group to a variety of nucleophiles such
as genetic bases and histones, as noted in the
Epigenetics bonus Webinar
The process produces a strong alkylating reagent that can
add an methyl group to a variety of nucleophiles such
as genetic bases and histones, as noted in the
Epigenetics bonus Webinar
Thioethers / Sulfides
Thioethers / Sulfides
Methylation of cytosine, a genetic base:
Nucleophilic substitution of SAM-CH3
(SAM = S-adenosylmethionine)
Where cytosine is the nucleophile.
Sulfide reactions:
Oxidation: sodium meta-periodate produces a sulfoxide.
Thioethers / Sulfides
Consider the IR of dimethylsulfoxide (DMSO) and the resonance structures
below it. An S=O bond has a strong peak @ ~1050 cm-1 and an S-O
bond @ 700-900 cm-1. Which resonance form should predominate?
Question
What is the correct order of reagents needed for the
following transformation?
Thioethers / Sulfides
Sulfide reactions:
Oxidation: hydrogen peroxide produces a sulfone.