Química Orgânica I ROR; RSR

38 Pages·2007·1.8 MB·Portuguese

Química Orgânica I
Ciências Farmacêuticas
Bioquímica
Química
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R-O-R; R-S-R
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1
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diethyl ether
Ethoxyethane (diethyl ether):
Formally used as an anesthetic
Explosive when mixed with air.
Oxacyclopropane (oxirane, ethylene oxide)
Industrial chemical intermediate
Fumigating agent for seeds and grains
Oxacyclopropane derivatives control insect
metamorphosis and are formed during enzyme-
catalyzed oxidations of aromatic hydrocarbons (highly
carcinogenic).
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Types of ethers
• Formula R-O-R where R is alkyl or aryl.
• Symmetrical or unsymmetrical
• Examples:
CH O CH O
3 3
O CH
3
=>
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IUPAC nomenclature of ethers
(cid:1)
system: ethers are alkoxyalkanes
(Ethers are alkanes bearing an alkoxy
substituent)
(cid:2) The larger substituent is the stem and
the smaller substituent is the alkoxy
group (methoxyethane)
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CCHH OOCCHH CCHH
33 22 33
mmeetthhooxxyyeetthhaannee CCHH CCHH OOCCHH CCHH CCHH CCll
33 22 22 22 22
11--cchhlloorroo--33--eetthhooxxyypprrooppaannee
CCHH CCHH OOCCHH CCHH
33 22 22 33
eetthhooxxyyeetthhaannee
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CCHH OOCCHH CCHH
33 22 33
eetthhyyll mmeetthhyyll eetthheerr CCHH CCHH OOCCHH CCHH CCHH CCll
33 22 22 22 22
33--cchhlloorroopprrooppyyll eetthhyyll eetthheerr
CCHH CCHH OOCCHH CCHH
33 22 22 33
ddiieetthhyyll eetthheerr
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Cyclic ethers
Cyclic ethers names are based on the oxacycloalkane stem.
Oxacyclopropane (oxiranes, epoxides, ethylene oxides)
Oxacyclobutane
Oxacyclopentane (tetrahydrofurans)
Oxacyclohexanes (tetrahydropyrans)
Ring numbering starts on the oxygen atom.
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NNaammeess ooff CCyycclliicc EEtthheerrss

OO OO
OO
OOxxiirraannee OOxxeettaannee OOxxoollaannee
((EEtthhyylleennee ooxxiiddee)) ((tteettrraahhyyddrrooffuurraann))

OO
OO
OO
OOxxaannee 11,,44--DDiiooxxaannee
((tteettrraahhyyddrrooppyyrraann))
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Common ethers
Cyclic ethers are members of the class of cycloalkanes called
heterocycles in which one or more carbon atoms have been
replaced by a heteroatom.
Except for strained cyclical derivatives, ethers are fairly
unreactive and are often used as solvents in organic reactions.
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crown ethers
Cyclic polyethers based on the 1,2-ethanediol unit are called
crown ethers. The crown ether, 18-crown-6, contains 18 total
atoms and 6 oxygen atoms:
Note that the inside of the ring is electron rich.
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Structure and Polarity
(cid:1) Bent molecular geometry
(cid:1) Oxygen is sp3 hybridized
(cid:1) Tetrahedral angle
=>
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BBoonndd aanngglleess aatt ooxxyyggeenn aarree sseennssiittiivvee
ttoo sstteerriicc eeffffeeccttss

OO OO
HH HH CCHH HH
33
110055°° 110088..55°°

OO OO
CCHH CCHH ((CCHH )) CC CC((CCHH ))
33 33 33 33 33 33
111122°° 113322°°
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AAnn ooxxyyggeenn aattoomm aaffffeeccttss ggeeoommeettrryy iinn mmuucchh tthhee
ssaammee wwaayy aass aa CCHH ggrroouupp
22
mmoosstt ssttaabbllee ccoonnffoorrmmaattiioonn ooff ddiieetthhyyll eetthheerr
rreesseemmbblleess ppeennttaannee
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AAnn ooxxyyggeenn aattoomm aaffffeeccttss ggeeoommeettrryy iinn mmuucchh tthhee
ssaammee wwaayy aass aa CCHH ggrroouupp
22
mmoosstt ssttaabbllee ccoonnffoorrmmaattiioonn ooff tteettrraahhyyddrrooppyyrraann
rreesseemmbblleess ccyycclloohheexxaannee
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Hydrogen Bond Acceptor
(cid:1) Ethers cannot H-bond
to each other.
(cid:1) In the presence of
-OH or -NH (donor),
the lone pair of
electrons from ether
forms a hydrogen
bond with the -OH or
-NH.
=>
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Solvent Properties
• Nonpolar solutes
dissolve better in ether
than in alcohol.
• Ether has large dipole
moment, so polar
solutes also dissolve.
• Ethers solvate cations.
• Ethers do not react with
strong bases.
=>
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Boiling Points
Similar to alkanes of comparable molecular weight.
=>
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Solubility
The smaller alkoxyalkanes are water soluble, however
solubility decreases with increasing hydrocarbon size.
Methoxymethane – completely water soluble
Ethoxyethane – 10% aqueous solution
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