chemistry 343 chapter 8

8/17/2019 Chemistry 343 Chapter 8

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Chapter 8: Addition Reactions• Addition Reactions to Alkenes (Section 8.1)•

Markovnikov’s Rule (Section 8.2)• Stereochemistr o! "onic Addition to Alkenes (Section 8.#)• $2S%& Additions to Alkenes (Section 8.&)

• $2% Additions to Alkenes (Section 8.')

• %mercuration*emurcuration (Section 8.+)• $dro,oration%idation (Section 8.-)• Addition o! r2 and Cl2 to Alkenes (Section 8.12)

• Stereochemistr o! *ihalide Additions (Section 8.1#)• $alohdrin /ormation 0et Addition o! 3%$4 (Section 8.1&)

• *ivalent Car,on Compounds: Car,enes (Section 8.1')• %idations o! Alkenes (Sections 8.1+38.1-)• Additions to Alknes (Sections 8.1838.15)• %idative Cleava6e o! Alknes (Section 8.27)

• Applications in Snthesis (Section 8.21)Chapter 8 Relevant et: 9a6es #283#-+


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Addition Reactions: Addition to Alkenes

C C A C C AAddition

• $ave Alread ooked at Addition o! $2 ($dro6enation)

• ;ill o< Add Additional Rea6ents to %ur Arsenal

$ ("= r= Cl)

$2S%&

$2%

r2

Cl2

"2


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;h *o Additions to Alkenes ;ork>

• Conversion o! π ond to 2 σ onds picall ?ner6 /avored

•


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Addition Reactions: $ to Alkenes

C C

$ .r

$ .r $ .r

• Beneral %rder o! $ Reactivit:

$" $r $Cl $/

• Dsuall *issolved in Solvent (C$#C%2$= C$2Cl2)

• Can ,e u,,led hrou6h Solution as a Bas

• Addition o! $Cl not Benerall Dse!ul (;orks


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Addition Reactions: $r to Alkenes

C C

$ .r

$ .r $ .r

• π ond (ucleophile) 9rotonate Car,ocation "ntermediate

• Car,ocation Captured , rE (ucleophile) $r Added

• $r (or other $) Addition in


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Markovnikov’s Rule: $r to Alkenes

$r

C$2Cl2= 7oC

r

r

MAH%R M"%R (RAC?)

• 23romopropane is MaIor 9roduct

• %nl er Small Amount o! 13romopropane %,served

• rue ;ith %ther Alkenes

$r

C$2Cl2= 7oC

r

r

MAH%R M"%R (8RAC?)


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Markovnikov’s Rule: ;h>

$r

C$2Cl2= 7oC

r

r

MAH%R M"%R (RAC?)

• 9roduct *istri,ution ?plained ;hen ookin6 at "ntermediates

• Recall *iscussion o! Car,ocation Sta,ilit (2J 1J)

• MaIor 9roduct /ormed /rom More Sta,le C@ "ntermediate

$ r

$

$

ess Sta,leCar,ocation

More Sta,leCar,ocation


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Markovnikov’s Rule: C@ Sta,ilit

• ;e Gno< 2J Car,ocations More Sta,le han 1J

• MaIor 9roduct /ormed /rom More Sta,le C@ "ntermediate

• Means S in 2J Car,ocation 9ath


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Markovnikov’s Rule: Summar

In the ionic additions of an unsymmetricalreagent to a double bond, the positive portion

of the adding reagent attaches itself to a

carbon atom of the double bond so as to yield

the MORE STABE !ARBO!ATIO" as an I"TERME#IATE

MARG%"G%’S RD?:

" Cl"

Cl

"

Cl

" Cl

Recall ond 9olariKation:

This Addition $%reference& is !alled RE'IOSEE!TI(IT)


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$2S%& Addition to Alkenes

• Must Add C%* Sul!uric AcidL /orm Alkl $dro6en Sul!ates

• Re6ioselective Reaction: %,es Markovnikov’s Rule

• ote Mechanistic Similarities


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Alcohols /rom Alkl $dro6en Sul!ates

• $F*R%FS"S Reaction o! Alkl $dro6en Sul!ate

• Simpl $eat the Sul!ate in ;ater

• et Reaction is Markovnikov Addition o! $2% to Alkene

• Dsed in %ne "ndustrial ?thanol Makin6 9rocess

%S%#$$$2%

∆

%$$


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%mercuration3*emercuration

C C @ $2% @ $6(%Ac)2

$6%Ac%$

$/

$6%Ac%$

a%$= a$&

$%$

%FM?RCDRA"%:

*?M?RCDRA"%:

• et Reaction: Markovnikov Addition o! $2% to Alkene

• oth Reactions uite RapidL Alcohol Fields Dsuall 57N

• a$&: Sodium orohdride O$EP *eliverin6 A6ent


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%mercuration3*emercuration (2)

C C

$

$9r

$$6(%Ac)

2

$

$

$6%Ac

$

9r

%$

a%$= a$&$/$2%

$

$

$

$

9r

%$

$6(%Ac)2 a%$= a$&

$/$2%

Me %$$6%Ac

$

Me %$$

$

• Added ene!it o! %mercuration*emercuration:

C@ R?ARRAB?M?S Seldoml %,served

Consider ?ample Seen on et Slide


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%mercuration3*emercuration (#)

• ;ould ?pect 2J Car,ocation to Rearran6e to #J

• Added C@ Sta,iliKation !rom $6 Atom 9revents Rearran6ment

• Dse!ul $dration 9rocess !or Avoidin6 Skeletal Mi6rations

1. $6(%Ac)2=

2. a%$= a$&

$/$2%

%$

$6%Ac$6 Sta,iliKation

$6%Ac


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$dro,orationQ%idation Reactions

$# : 8$/$dro,oration

(C$#C$2C$2)# $2%2= a%$%idation

%$

• $dro,oration: Addition o! $ and to Alkene

• eutral oron has # Coordination Sites

Bet rialkl oranes as an "ntermediate (ripropl,orane)

• %idation: $2%2= a%$ %idiKe to rialkl,orate ?ster

• %idation /ollo


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$dro,orationQ%idation Reactions (2)

;e Mentioned anti3Markovnikov Re6iochemistr

Reaction also 9roceeds


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Addition o! Cl2 and r2 to Alkenes

• %,tain icinal *ihalides as Reaction 9roducts

• ;ant to use a on3ucleophilic Solvent (*ue to "ntermediate)

"mportant to Run Reactions in *ark (Avoid Radicals)

$#C$C C$C$#Cl2

35 oC

$#C$C C$C$#

Cl Cl

$#C$2C$C C$2Cl2

35 oC

$#C$2C$C C$2

ClCl

r2

3' oC

r

$

r

$@ ?nantiomer


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Beneral Mechanism o! *ihalide Addition

• "ntermediate is a R%M%"DM "% (in r2 Case)

• ucleophilic Solvents Can Capture (%pen) romonium "on

romonium "on %penin6 is S2 Anti Addition o! r2

C C

.r

.r

3.r3.r

.r

.r

.r


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Stereochemistr o! *ihalide Additions

• Can %pen Smmetric romonium "ons at ?ither Car,on

• Al


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$alohdrin /ormation

• "ntermediate is Still a R%M%"DM "% (in r2 Case)

• ucleophilic Solvents Can Capture (%pen) romonium "on

$2% %pens the romonium "onL Another $2% *eprotonates

9roduct is $alohdrin et 3%$ Addition to Alkene

Still Can Bet Stereoisomeric 9roducts (%pen ?ither ?nd)

C C

r

r

3r3r

$2%

$%

r3$@


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*ivalent Car,on Compounds: Car,enes

C$2 1 1 $eat or :i6ht C$2 1 1@

*iaKomethane Methlene

(A Car,ene)

• Common ;a o! Beneratin6 Car,enes (*ivalent Car,on)

• *iaKomethane: # Resonance Structures (*ra< %thers>>)

•

Car,enes are $i6hl Reactive SpeciesL Short3ived

• ?cellent Dtilit is in the Snthesis o! Cclopropanes

• et’s ook at Some Reactions Makin6 Dse o! Car,enes


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*ivalent Car,on Compounds: Car,enes

C$2C C @ C CC$2

G%C(C$#)#

C$Cl#

Cl

Cl

C$2"2= n(Cu)

• $alo6en Su,stituted Car,enes !rom $alo!orms (C$Cl#= etc.)

• ast Reaction is Called the OSimmons3SmithP Reaction


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%idation: Sn *ihdrolation

• CTC is %idiKed , %s%&

• Addition o! $drol Broups 9roceeds


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%idation: Sn *ihdrolation (2)

•

Sn Addition *ue to '3Centered ransition State

• ransition State Same !or GM%& %idations

• Cleava6e o! %smate ?ster *oes ot Chan6e C3% Stereochem

%

%s

%

% %

%s%&= 2'oC

9ridine

%smate ?ster


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%idative Cleava6e o! Alkenes

• *iol elieved to ,e "ntermediate in Cleava6e Reaction

• Dnsu,stituted Alkene Car,ons %idiKed to Car,on *ioide

• Monosu,stituted Alkene Car,ons %idiKed to Car,olates

• *isu,stituted Alkene Car,ons %idiKed to Getones

GMn%&= a%$

$2%= %

%

1. GMn%&= a%$

2. $#%@

%

+ % C %

2


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%Konolsis o! Alkenes

?t

Me Me

1. %#= C$2Cl2= 3-8 oC

2. n$%Ac

%

?t

Me

Me $

%

@

Me

1. %#= C$2Cl2= 3-8oC

2. n$%AcMe

%

%

$

• Milder Conditions than reatin6


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*ihalide Addition o Alknes

• Addition Reactions= Hust as in Alkenes (adds %nce or


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Addition o! $ to Alknes

• Addition Reactions= Hust as in Alkenes (adds %nce or


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%idative Cleava6e o! Alknes

• Can Dse ?ither %Konolsis or GMn%& as


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Anti3Markovnikov $r Addition

• Addition o! 9eroides (R%%R) A"3MARG%"G%

• Boes hrou6h a Radical Mechanism (Chapter 17)

• Ri6ht o< /ocus on Re6iochemistr (Gno< the Reaction)

Me $$r

r

$

Me

$

peroides

$r

peroides

r

chemistry 343 chapter 8

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