hidrocarbon alkenes and reactions
TRANSCRIPT
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Chapter 7 1
IUPAC Nomenclature
Parent is longest chain containingthe double bond.
-ane changes to -ene. (or -diene,-triene)
Number the chain so that the double
bond has the loest possiblenumber.
In a ring, the double bond isassumed to be beteen carbon 1
and carbon !.
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Chapter 7 !
Name $hese Al%enes
CH2 CH CH2 CH3
CH3 C
CH3
CH CH3
CH3
CHCH2CH3
H3C
1-butene
!-meth&l-!-butene
'-meth&lc&clopentene
!-sec-but&l-1,'-c&cloheadiene
'-n-prop&l-1-heptene"#
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Chapter 7 '
Al%ene ubstituents
= CH2
methylene
(methylidene)
- CH = CH2
vinyl
(ethenyl)
- CH2- CH = CH2
allyl
(2-propenyl)
Name:
"#
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Chapter 7 *
Common Names
Usuall& used +or small molecules.
amples
CH2 CH2
ethylene
CH2 CH CH3
propylene
CH2 C CH3
CH3
isobutylene
=>
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Chapter 7
Cis-trans Isomerism
imilar groups on same side o+double bond, al%ene is cis.
imilar groups on opposite sides o+
double bond, al%ene is trans. C&cloal%enes are assumed to be cis.
$rans c&cloal%enes are not stable
unless the ring has at least /carbons.
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Chapter 7 0
Name these
C C
CH3
H
H
CH3CH2
C C
Br
H
Br
H
trans-2-pentene cis-1,2-dibromoethene
"#
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Chapter 7 7
E-ZNomenclature
Use the Cahn-Ingold-Prelog rules toassign priorities to groups attached
to each carbon in the double bond. I+ high priorit& groups are on the
same side, the name isZ(+or
zusammen). I+ high priorit& groups are on
opposite sides, the name is E(+or
entgegen).
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Chapter 7 /
ample, E-Z
C CH3C
H
Cl
CH2C C
H
H
CH CH3
Cl1
2
1
2
2Z
2
1
1
2
5E
(2Z, 5E)-3,7-dichloro-2,5-octadiene"#
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Chapter 7
Commercial Usesth&lene
=>
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Chapter 7 12
Commercial UsesProp&lene
=>
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Chapter 7 11
3ther Pol&mers
=>
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Chapter 7 1!
tabilit& o+ Al%enes 4easured b& heat o+ h&drogenation
Al%ene 5 6! Al%ane 5 energ&
4ore heat released, higher energ&al%ene.
"
30.3 kcal
27.6 kcal
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Chapter 7 1'
ubstituent ects
4ore substituted al%enes are morestable.H2C=CH2 < R-CH=CH2< R-CH=CH-R < R-CH=CR2ranched al%enes ha
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Chapter 7 1/
Polarit& amples
= 0.33 = 0
=>
cis-2-butene, bp 4 !C
C C
H
H3C
H
CH3
trans-2-butene, bp 1 !
C C H
H
H3C
CH3
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Chapter /@eactions o+ Al%enes
Organic Chemistry
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Chapter / !2
@eacti
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Chapter / !1
lectrophilic Addition
tep 1 Pi electrons attac% theelectrophile.
C C+
E+
C
E
C +
C
E
C + + Nuc:
_
C
E
C
Nuc
=>
tep ! Nucleophile attac%s the carbocation.
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Chapter / !!
$&pes o+ Additions
=>
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Chapter / !'
Addition o+ 6B (1)
Protonation o+ double bond &ields themost stable carbocation. Positi
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Chapter / !*
Addition o+ 6B (!)
CH3 C
CH3
CH CH3
H Br
CH3 C
CH3
CH CH3
H+
+ Br_
CH3 C
CH3
CH CH3
H+
Br_
CH3 C
CH3
CH CH3
HBr
"#
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Chapter / !
@egiospecicit&
4ar%o
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Chapter / !0
=ree-@adicalAddition o+ 6>r
In the presence o+ peroides, 6>radds to an al%ene to +orm the
Danti-4ar%o
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Chapter / !7
=ree @adical Initiation
Peroide 3-3 bond brea%s easil& to+orm +ree radicals.
#R H Br R H # Br
R R +R R heat
6&drogen is abstracted +rom 6>r.
Electrophile
"#
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Chapter / !/
Propagation teps
>romine adds to the double bond.
#C
Br
C H Br# C
Br
C
H
Br
Electrophile =!
CBr
CC CBr #
6&drogen is abstracted +rom 6>r.
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Chapter / !
Anti-4ar%o
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Chapter / '2
6&dration o+ Al%enes
@e
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Chapter / '1
4echanism +or6&dration
+C
H
C+
H2 C
H
C
H
H+
+ H2CH
C H
H+
C
H
C
H
H3++ "#
C C H H
H
++ + H2C
H
C+
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Chapter / '!
3rientation +or 6&dration
4ar%o
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Chapter / ''
Indirect 6&dration
3&mercuration-:emercuration 4ar%o
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Chapter / '*
6&drogenation
Al%ene 5 6! Al%ane
Catal&st reGuired, usuall& Pt, Pd, orNi.
=inel& di
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Chapter / '
Addition o+ Carbenes
Insertion o+ -C6!group into a double
bond produces a c&clopropane ring.
$hree methods :ia9omethane
immons-mith meth&lene iodide andHn(Cu)
Alpha elimination, halo+orm
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Chapter / '0
:ia9omethane
tremel& toic and eplosi
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Chapter / '7
Addition o+ 6alogens
Cl!, >r!, and sometimes I!add to a
double bond to +orm a
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Chapter / '/
4echanism +or6alogenation
Pi electrons attac% the brominemolecule.
A bromide ion splits o.
Intermediate is a c&clic bromoniumion.
CC + Br Br CC
Br
# Br "#
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Chapter / '
4echanism (!)
6alide ion approaches +rom sideopposite the three-membered ring.
CC
Br
Br
CC
Br
Br
=>
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Chapter / *2
$est +or Unsaturation
Add >r!in CCl*(dar%, red-bron color) to
an al%ene in the presence o+ light.
$he color Guic%l& disappears as thebromine adds to the double bond.
D:ecolori9ing bromineE is the chemical test+or the presence o+ a double bond.
"#
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Chapter / *1
=ormation o+ 6aloh&drin
I+ a halogen is added in thepresence o+ ater, a haloh&drin is
+ormed. ater is the nucleophile, instead o+
halide.
Product is 4ar%o
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Chapter / *!
@egiospecicit&
$he most highl& substituted carbonhas the most positi
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Chapter / *'
Predict the Product
Predict the product hen the gi
H
CH3)
Cl
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Chapter / **
poidation
Al%ene reacts ith a pero&acid to+orm an epoide (also called
oirane). Usual reagent is pero&ben9oic
acid.CC
+ R C
H CC
R C
H+"#
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Chapter / *
4echanism
3ne-step concerted reaction.e
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Chapter / *0
poide tereochemistr&
ince there is no opportunit& +orrotation around the double-bonded
carbons, cisor transstereochemistr& is maintained.
CCCH3 CH3
H H*h C
H
CCCH3 CH3
H H "#
3 i th
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Chapter / *7
3pening thepoide @ing
Acid catal&9ed.
ater attac%s the protonatedepoide.
$rans diol is +ormed.
CC
H3+
CC
H
H2
CC
H
H H H2
CC
H
H
"#
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Chapter / */
3ne-tep @eaction
$o s&nthesi9e the gl&col ithoutisolating the epoide, use aGueous
pero&acetic acid or pero&+ormicacid.
$he reaction is stereospecic.
CH3CH
H
H
H
H
"#
6 d l ti
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Chapter / *
&n 6&dro&lationo+ Al%enes
Al%ene is con
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Chapter / 2
4echanism ith 3s3*
Concerted synaddition o+ too&gens to +orm a c&clic ester.
C
Cs
C
C
s
C
C
H
H# s4
H22"#
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Chapter / 1
tereospecicit&
I+ a chiral carbon is +ormed, onl& onestereoisomer ill be produced (or a
pair o+ enantiomers).
C
C
CH2CH3
H CH2CH3
C
C
CH2CH3
CH2CH3
H
H
H
HH2
2
H
2
1 s4
cis-3-heene meso-3,4-he"ne$iol
"#
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Chapter / !
3idati
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Chapter / '
Clea
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Chapter / *
ample
CCCH3 CH3
H CH3 ./n4
0"r&, concC C
CH3
CH3
HH
H3C
H
C
H3C
H
C
CH3
CH3
C
H3CH
#
"#
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Chapter /
39onol&sis
@eaction ith o9one +orms ano9onide.
39onides are not isolated, but aretreated ith a mild reducing agentli%e Hn or dimeth&l sulde.
4ilder oidation thanpermanganate.
Products +ormed are %etones or
aldeh&des.
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Chapter / 0
39onol&sis ample
CCCH3 CH3
H CH3 3C
H3C
H
CCH3
CH3
%oni$e
#
CH32
CH3C
H
C
CH3
CH3
CH3
CH3
)/
"#
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Chapter / 7
Pol&meri9ation
An al%ene (monomer) can add toanother molecule li%e itsel+ to +orm achain (pol&mer).
$hree methods Cationic, a carbocation intermediate
=ree radical
Anionic, a carbanion intermediate (rare)
"#
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Chapter / /
Cationic Pol&meri9ation
lectrophile, li%e 65or >=', adds to
the least substituted carbon o+ an
al%ene, +orming the most stablecarbocation.
C CCH3
H
H
H
H
H
H
C
H
H
H
C
CH3
H
+ C CCH3
H
H
H
C
H
H
H
C
CH3
H
C
H
H
C
CH3
H
"#
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@adical Pol&meri9ation
In the presence o+ a +ree radicalinitiator, li%e peroide, +ree radical
pol&meri9ation occurs.
C C*h
H
H
H
R
C
H
R
H
C
*h
H
+ C C*h
H
H
H
C
H
R
H
C
*h
H
C
H
H
C
*h
H
"#