有机化学英文课件chapter11
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is n o t s u p p o r te d
11-13
Preparation of Ethers
Acid-catalyzed addition of alcohols to alkenes
• yields are highest using an alkene that can form a stable carbocation
• Step 1: proton transfer to the oxygen atom of the ether gives an oxonium ion
M a c in to s h P IC T im a g e fo r m a t
is n o t s u p p o r te d
• Step 2: nucleophilic displacement on the 1° carbon gives a haloalkane and an alcohol
M a c in to s h P IC T im a g e fo rm a t
is n o t s u p p o rte d
M a c in to s h P IC T im a g e fo rm a t
is n o t s u p p o r te d
11-10
Preparation of Ethers
M a c in to s h P IC T im a g e fo r m a t
is n o t s u p p o r te d
11-11
Preparation of Ethers
• Step 1: proton transfer gives an oxonium ion
M a c in to s h P IC T im a g e fo r m a t
11-17
Cleavage of Ethers
A dialkyl ether is cleaved to two moles of haloalkane
M a c in to s h
P IC T
im a g e
fo rm a t
is
n o t s u p p o rte d
11-18
Cleavage of Ethers
11-14
Preparation of Ethers
• Step 1: protonation of the alkene gives a carbocation
M a c in to s h P IC T im a g e fo r m a t
is n o t s u p p o r te d
• Step 2: reaction of the carbocation (an electrophile) with the alcohol (a nucleophile) gives an oxonium ion
is n o t s u p p o r te d
11-6
Physical Properties
Although ethers are polar compounds, only weak dipole-dipole attractive forces exist between their molecules in the pure liquid state
OCH2 CH3
CH3
trans-2-Ethoxy-
2-Methoxy-2-
cyclohexanol
methylpropane
(tert-Butyl methyl ether)
11-5
Nomenclature: ethers
Although cyclic ethers have IUPAC names, their common names are more widely used
Organic Chemistry
William H. Brown Christopher S. Foote Brent L. Iverson
11-1
Ethers &
Macintosh PICTEpoxides
image format
is not supported
Chapter 11
Macintosh PICT image format is not supported
M a c in to s h P IC T im a g e fo rm a t
is n o t s u p p o rte d
11-15
Preparation of Ethers
Step 3: proton transfer to solvent completes the reaction
M a c in to s h P IC T im a g e fo r m a t
• and using methanol or a 1° alcohol that is not prone to undergo acid-catalyzed dehydration
M a c in to s h P IC T im a g e fo rm a t
is n o t s u p p o rte d
M a c in to s h P IC T im a g e fo r m a t
is n o t s u p p o r te d
11-9
Preparation of Ethers
• yields are highest with methyl and 1° halides, • lower with 2° halides (competing -elimination) • reaction fails with 3° halides (-elimination only)
• they are more soluble in H2O than are hydrocarbons
11-8
Preparation of Ethers
Williamson ether synthesis: SN2 displacement of halide, tosylate, or mesylate by alkoxide ion
11-7
Physical Properties
Boiling points of ethers are
• lower than alcohols of comparable MW • close to those of hydrocarbons of comparable MW
Ethers are hydrogen bond acceptors
M a c in to s h P IC T im a g e fo r m a t
is n o t s u p p o r te d
• the alcohol is then converted to an haloalkane by
another SN2 reaction
11-19
Cleavage of Ethers
M a c in to s h P IC T im a g e fo r m a t
is n o t s u p p o r te d
11-4
Nomenclature: ethers
IUPAC: the longest carbon chain is the parent
• name the OR group as an alkoxy substituent
s u p p o r te d
• cleavage requires both a strong acid and a good nucleophile; therefore, the use of concentrated HI (57%) and HBr (48%)
• cleavage by concentrated HCl (38%) is less effective, primarily because Cl- is a weaker nucleophile in water than either I- or Br-
Acid-catalyzed dehydration of alcohols
• diethyl ether and several other ethers are made on an industrial scale this way
• a specific example of an SN2 reaction in which a poor leaving group (OH-) is converted to a better one (H2O)
11-2
Structure
The functional group of an ether is an oxygen atom bonded to two carbon atoms
• in dialkyl ethers, oxygen is sp3 hybridized with bond angles of approximately 109.5°.
is n o t s u p p o r te d
11-12
Preparation of Ethers
Step 3: proton transfer to solvent completes the reaction
M a c in to s h P IC T im a g e fo r m a t
• IUPAC: prefix ox- shows oxygen in the ring • the suffixes -irane, -etane, -olane, and -ane show three,
four, five, and six atoms in a saturated ring
M a c in to s h P IC T im a g e fo r m a t
is n o t s u p p o r te d
11-16
Cleavage of Ethers
Ethers are cleaved by HX to an alcohol and a haloalkane
M a c in t o s h
P IC T
im a g e
fo r m a t
is
not
Common names: name the groups bonded to oxygen in alphabetical order followed by the word ether
CH3 CH2 OCH2 CH3
Ethoxyethane (Diethyl ether)
OH
CH3
CH3 OCCH3
3°, allylic, and benzylic ethers are particularly sensitive to cleavage by HX
• tert-butyl ethers are cleaved by HCl at room temp • in this case, protonation of the ether oxygen is
• in dimethyl ether, the C-O-C bond angle is 110.3°
M acin to sh P IC T im ag e fo rm at
is n o t su p p o rted
M a c in to Байду номын сангаас h P IC T im a g e fo rm a t
is n o t s u p p o rte d
11-3
Structure
• in other ethers, the ether oxygen is bonded to an sp2 hybridized carbon
• in ethyl vinyl ether, for example, the ether oxygen is bonded to one sp3 hybridized carbon and one sp2 hybridized carbon
is n o t s u p p o r te d
• Step 2: nucleophilic displacement of H2O by the OH group of the alcohol gives a new oxonium ion
M a c in to s h P IC T im a g e fo r m a t
11-13
Preparation of Ethers
Acid-catalyzed addition of alcohols to alkenes
• yields are highest using an alkene that can form a stable carbocation
• Step 1: proton transfer to the oxygen atom of the ether gives an oxonium ion
M a c in to s h P IC T im a g e fo r m a t
is n o t s u p p o r te d
• Step 2: nucleophilic displacement on the 1° carbon gives a haloalkane and an alcohol
M a c in to s h P IC T im a g e fo rm a t
is n o t s u p p o rte d
M a c in to s h P IC T im a g e fo rm a t
is n o t s u p p o r te d
11-10
Preparation of Ethers
M a c in to s h P IC T im a g e fo r m a t
is n o t s u p p o r te d
11-11
Preparation of Ethers
• Step 1: proton transfer gives an oxonium ion
M a c in to s h P IC T im a g e fo r m a t
11-17
Cleavage of Ethers
A dialkyl ether is cleaved to two moles of haloalkane
M a c in to s h
P IC T
im a g e
fo rm a t
is
n o t s u p p o rte d
11-18
Cleavage of Ethers
11-14
Preparation of Ethers
• Step 1: protonation of the alkene gives a carbocation
M a c in to s h P IC T im a g e fo r m a t
is n o t s u p p o r te d
• Step 2: reaction of the carbocation (an electrophile) with the alcohol (a nucleophile) gives an oxonium ion
is n o t s u p p o r te d
11-6
Physical Properties
Although ethers are polar compounds, only weak dipole-dipole attractive forces exist between their molecules in the pure liquid state
OCH2 CH3
CH3
trans-2-Ethoxy-
2-Methoxy-2-
cyclohexanol
methylpropane
(tert-Butyl methyl ether)
11-5
Nomenclature: ethers
Although cyclic ethers have IUPAC names, their common names are more widely used
Organic Chemistry
William H. Brown Christopher S. Foote Brent L. Iverson
11-1
Ethers &
Macintosh PICTEpoxides
image format
is not supported
Chapter 11
Macintosh PICT image format is not supported
M a c in to s h P IC T im a g e fo rm a t
is n o t s u p p o rte d
11-15
Preparation of Ethers
Step 3: proton transfer to solvent completes the reaction
M a c in to s h P IC T im a g e fo r m a t
• and using methanol or a 1° alcohol that is not prone to undergo acid-catalyzed dehydration
M a c in to s h P IC T im a g e fo rm a t
is n o t s u p p o rte d
M a c in to s h P IC T im a g e fo r m a t
is n o t s u p p o r te d
11-9
Preparation of Ethers
• yields are highest with methyl and 1° halides, • lower with 2° halides (competing -elimination) • reaction fails with 3° halides (-elimination only)
• they are more soluble in H2O than are hydrocarbons
11-8
Preparation of Ethers
Williamson ether synthesis: SN2 displacement of halide, tosylate, or mesylate by alkoxide ion
11-7
Physical Properties
Boiling points of ethers are
• lower than alcohols of comparable MW • close to those of hydrocarbons of comparable MW
Ethers are hydrogen bond acceptors
M a c in to s h P IC T im a g e fo r m a t
is n o t s u p p o r te d
• the alcohol is then converted to an haloalkane by
another SN2 reaction
11-19
Cleavage of Ethers
M a c in to s h P IC T im a g e fo r m a t
is n o t s u p p o r te d
11-4
Nomenclature: ethers
IUPAC: the longest carbon chain is the parent
• name the OR group as an alkoxy substituent
s u p p o r te d
• cleavage requires both a strong acid and a good nucleophile; therefore, the use of concentrated HI (57%) and HBr (48%)
• cleavage by concentrated HCl (38%) is less effective, primarily because Cl- is a weaker nucleophile in water than either I- or Br-
Acid-catalyzed dehydration of alcohols
• diethyl ether and several other ethers are made on an industrial scale this way
• a specific example of an SN2 reaction in which a poor leaving group (OH-) is converted to a better one (H2O)
11-2
Structure
The functional group of an ether is an oxygen atom bonded to two carbon atoms
• in dialkyl ethers, oxygen is sp3 hybridized with bond angles of approximately 109.5°.
is n o t s u p p o r te d
11-12
Preparation of Ethers
Step 3: proton transfer to solvent completes the reaction
M a c in to s h P IC T im a g e fo r m a t
• IUPAC: prefix ox- shows oxygen in the ring • the suffixes -irane, -etane, -olane, and -ane show three,
four, five, and six atoms in a saturated ring
M a c in to s h P IC T im a g e fo r m a t
is n o t s u p p o r te d
11-16
Cleavage of Ethers
Ethers are cleaved by HX to an alcohol and a haloalkane
M a c in t o s h
P IC T
im a g e
fo r m a t
is
not
Common names: name the groups bonded to oxygen in alphabetical order followed by the word ether
CH3 CH2 OCH2 CH3
Ethoxyethane (Diethyl ether)
OH
CH3
CH3 OCCH3
3°, allylic, and benzylic ethers are particularly sensitive to cleavage by HX
• tert-butyl ethers are cleaved by HCl at room temp • in this case, protonation of the ether oxygen is
• in dimethyl ether, the C-O-C bond angle is 110.3°
M acin to sh P IC T im ag e fo rm at
is n o t su p p o rted
M a c in to Байду номын сангаас h P IC T im a g e fo rm a t
is n o t s u p p o rte d
11-3
Structure
• in other ethers, the ether oxygen is bonded to an sp2 hybridized carbon
• in ethyl vinyl ether, for example, the ether oxygen is bonded to one sp3 hybridized carbon and one sp2 hybridized carbon
is n o t s u p p o r te d
• Step 2: nucleophilic displacement of H2O by the OH group of the alcohol gives a new oxonium ion
M a c in to s h P IC T im a g e fo r m a t