hidrocarbon alkenes and reactions

7/25/2019 Hidrocarbon Alkenes and Reactions

1/59

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 !.


2/59

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"#


3/59

Chapter 7 '

Al%ene ubstituents

= CH2

methylene

(methylidene)

- CH = CH2

vinyl

(ethenyl)

- CH2- CH = CH2

allyl

(2-propenyl)

Name:

"#


4/59

Chapter 7 *

Common Names

Usuall& used +or small molecules.

amples

CH2 CH2

ethylene

CH2 CH CH3

propylene

CH2 C CH3

CH3

isobutylene

=>


5/59

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.

"#


6/59

Chapter 7 0

Name these

C C

CH3

H

H

CH3CH2

C C

Br

H

Br

H

trans-2-pentene cis-1,2-dibromoethene

"#


7/59

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"#


9/59

Chapter 7

Commercial Usesth&lene

=>


10/59

Chapter 7 12

Commercial UsesProp&lene

=>


11/59

Chapter 7 11

3ther Pol&mers

=>


12/59

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


13/59

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


18/59

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


19/59

Chapter /@eactions o+ Al%enes

Organic Chemistry


20/59

Chapter / !2

@eacti


21/59

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.


22/59

Chapter / !!

$&pes o+ Additions

=>


23/59

Chapter / !'

Addition o+ 6B (1)

Protonation o+ double bond &ields themost stable carbocation. Positi


24/59

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

"#


25/59

Chapter / !

@egiospecicit&

4ar%o


26/59

Chapter / !0

=ree-@adicalAddition o+ 6>r

In the presence o+ peroides, 6>radds to an al%ene to +orm the

Danti-4ar%o


27/59

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

"#


28/59

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.


29/59

Chapter / !

Anti-4ar%o


30/59

Chapter / '2

6&dration o+ Al%enes

@e


31/59

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+


32/59

Chapter / '!

3rientation +or 6&dration

4ar%o


33/59

Chapter / ''

Indirect 6&dration

3&mercuration-:emercuration 4ar%o


34/59

Chapter / '*

6&drogenation

Al%ene 5 6! Al%ane

Catal&st reGuired, usuall& Pt, Pd, orNi.

=inel& di


35/59

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

"#


36/59

Chapter / '0

:ia9omethane

tremel& toic and eplosi


37/59

Chapter / '7

Addition o+ 6alogens

Cl!, >r!, and sometimes I!add to a

double bond to +orm a


38/59

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 "#


39/59

Chapter / '

4echanism (!)

6alide ion approaches +rom sideopposite the three-membered ring.

CC

Br

Br

CC

Br

Br

=>


40/59

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.

"#


41/59

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


42/59

Chapter / *!

@egiospecicit&

$he most highl& substituted carbonhas the most positi


43/59

Chapter / *'

Predict the Product

Predict the product hen the gi

H

CH3)

Cl


44/59

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+"#


45/59

Chapter / *

4echanism

3ne-step concerted reaction.e


46/59

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


47/59

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

"#


48/59

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


49/59

Chapter / *

&n 6&dro&lationo+ Al%enes

Al%ene is con


50/59

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"#


51/59

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

"#


52/59

Chapter / !

3idati


53/59

Chapter / '

Clea


54/59

Chapter / *

ample

CCCH3 CH3

H CH3 ./n4

0"r&, concC C

CH3

CH3

HH

H3C

H

C

H3C

H

C

CH3

CH3

C

H3CH

#

"#


55/59

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.


56/59

Chapter / 0

39onol&sis ample

CCCH3 CH3

H CH3 3C

H3C

H

CCH3

CH3

%oni$e

#

CH32

CH3C

H

C

CH3

CH3

CH3

CH3

)/

"#


57/59

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)

"#


58/59

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

"#


59/59

@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

"#

hidrocarbon alkenes and reactions

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