Chapter 8 Lecture - Organic Chemistry (11 Ed.) by Solomons

8/16/2019 Chapter 8 Lecture - Organic Chemistry (11 Ed.) by Solomons

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Created by Professor William Tam & Dr. Phillis

Chang

Chapter 8

Alkenes and Alkynes II:

Addition Reactions

Copyright © 2014 by John Wiley & Sons, Inc. All rights resere!.


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Table of Contents1. Addition Reactions of Alkenes

2. Electrophilic Addition of Hydrogen Halides to Alkenes: Mechanis! Marko"niko"#s R$le

%. &tereocheistry of the Ionic Addition to an Alkene'. Addition of (ater to Alkenes: Acid)Cataly*ed Hydration

+. Alcohols fro Alkenes thro$gh ,-yerc$ration/eerc$ration:Marko"niko" Addition

0. Alcohols fro Alkenes thro$gh Hydroboration,-idation: Anti)Marko"niko" &yn Hydration

. Hydroboration: &ynthesis of Alkylboranes

. ,-idation and Hydrolysis of Alkylboranes

3. &$ary of Alkene Hydration Methods

14. 5rotonolysis of Alkylboranes

11. Electrophilic Addition of 6roine ! Chlorine to Alkenes

12. &tereospeci7c Reactions

1%. Halohydrin 8oration

1'. /i"alent Carbon Copo$nds: Carbenes1+. ,-idation of Alkenes: &yn 192)/ihydro-ylation

10. ,-idati"e Clea"age of Alkenes

1. Electrophilic Addition of 6roine ! Chlorine to Alkynes

1. Addition of Hydrogen Halides to Alkynes

13. ,-idati"e Clea"age of Alkynes

24. Ho to 5lan a &ynthesis: &oe Approaches ! E-aples© 2014 by John Wiley & Sons, Inc. All rights resere!.


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1A.Ho To ;nderstand Additions

to Alkenes "his is an a!!ition reaction# $ – % a!!e! across the !oble bon!

'on!s bro(en 'on!s )or*e!

π+bon! σ+bon! 2 σ+bon!s

© 2014 by John Wiley & Sons, Inc. All rights resere!.

C C $ %&

$

C C

%&


4/65

Since π bon!s are )or*e! )ro* the oerlapping o) porbitals, π electron clo!s are aboe an! belo- theplane o) the !oble bon!

π electronclo!s


$lectrophilic electron see(ing

C/C an! CC π bon!s are particlarlyssceptible to electrophilic reagentselectrophiles

Co**on electrophiles

3, / Cl, 'r, I, 3g2, etc.

C C


5/65


C C$ %&

δ+

δ−

%&

C C

$


6/65

2. Electrophilic Addition: Marko"niko"#s R$le 5echanis*



7/65

5ar(oni(o’s 6le7or sy**etrical sbstrates, no

proble* )or regioche*istry


C C

3

3

3

3$ %&

$

CC 3

3

3

3

$

C C3

3

3

3

$

C C3

3

3

3

%& $

CC 3

3

3

3

%&

%&

sa*eas

sa*eas


8/65

5ar(oni(o’s 6le't )or nsy**etrical

sbstrates, t-o regioiso*ersare possible


$ %C C

3

3C

3

3 $

CC 3

3

C3

3

$

C CC3

3

3

3

$

C CC3

3

3

3

% $

CC 3

3

C3

3

%

% %

or

!i))erent

)ro*


9/65ote# carbocation stability ⇒ o 9 2o 9 1© 2014 by John Wiley & Sons, Inc. All rights resere!.

5ar(oni(o’s 6le In the electrophilic a!!ition o) an electrophile

across an nsy**etrical al(ene, the *orehighly sbstitte! an! *ore stabili:e!carbocation is )or*e! as the inter*e!iate inpre)erence to the less highly sbstitte! an!less stable one


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2A.Theoretical E-planation of Marko"niko"’s R$le

;ne -ay to state 5ar(oni(o’s rle is to

say that in the a!!ition o) 3 to anal(ene, the hy!rogen ato* a!!s to thecarbon ato* o) the !oble bon! thatalrea!y has the greater n*ber o)

hy!rogen ato*s© 2014 by John Wiley & Sons, Inc. All rights resere!.

3 C C

3

3C

3

3 δ+

δ−

3

CC 3

3

C3

3

3

C CC3

3

3

3

or

2o carbocation

*ore stable1

o carbocation

*ore stable

step 1slo-

r.!.s.

3 3


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<

Step 1 Step 2


3 'r

3 3

'r

'r

)ast1o cation

*inor

slo-

r.!.s.'r

)ast

3

'r

3

2o cation

*a


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$=a*ples


1 3 Cl

Cl

3

3

Cl

>? # ?

2

3 'r

>8 # 2

3

'r

'r

3


15/65

$=a*ples


1Cl ;3δ+

δ−

Cl

;3

Cl

;3

*a


16/65

$=a*ples


Cl

*a


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2C.Regioselecti"e Reactions

When a reaction that can potentially

yiel! t-o or *ore constittional iso*ersactally pro!ces only one or apre!o*inance o) one, the reaction is

sai! to be regioselecti"e


3 Cl Cl

3

3

Cl

>? # ?

*a


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2/. The A=TI)Marko"niko"’s R$le

@ia a ra!ical *echanis* see Chapter10

"his anti+5ar(oni(o a!!ition !oesnot ta(e place -ith 3I, 3Cl, an! 37,een -hen pero=i!es are present



19/65

&tereocheistry of the IonicAddition to an Alkene

achiral

trigonal planarcarbocation

attac( )ro* top

attac( )ro* botto*

r a c e * a t e


C C

3

3

'&

3 3 C C32 3

3

'

C C383

'&

S+2+3alohe=ane?0

C C33

'

R+2+3alohe=ane

?0


20/65

ddition of (ater to Alkenes:cid)Cataly*ed Hydration

7ollo-s 5ar(oni(oBsrle

;3 332;

!il&te 3;

e.g. !il&te 32S;4, 3;4

3 ;

3

3

*ore stable

o cation

slo-

step 1

3

32;

)ast

step 2

3

;3 3

32;)ast

step

3

;3

3 ;

3

3

'6 R t


21/65

'6.Rearrangeents

6earrange*ent can occr -ith certain

carbocations


32;

32S;43

1,2+al(yl shi)t

32;

;3

=,T


22/65

-yerc$ration/eerc$ration:arko"niko" Addition

Step 1# ;=y*ercration

Step 2# De*ercration


7ollo-s 5ar(oni(oBsrle

C C

3; 3g;Ac

C C3g;Ac2

"37+32;


23/65

2. ,-yerc$ration – /eerc$ration

32;

32S;4

;3

3

e.g.

;

3

3 3

3

1,2+al(yl shi)t

332;

;3

3

32;

32;

32S;4


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6earrange*ents o) the carbons(eleton sel!o* occr in

o=y*ercrationE!e*ercration

no rearrange*ent


3

;3

1. 3g;Ac2, "37+32;

2. %a'34

3g;Ac

;3

ia

+C M h i f


25/65

+C. Mechanis of,-yerc$ration Does not n!ergo a F)ree carbocationG

32; attac(s the carbon o) the bri!ge! 3g

ion that is better able to bear the partiale charge


3g;A

δ+

δ+

Ac;

3;

3g;Ac

32;

32;

h i


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Stereoche*istryHsally anti+a!!ition


32;

;3

C3

3

3g;Ac


27/65

Solo*ercration+De*ercration



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. Hydroboration,-idation:Anti)Marko"niko" &yn Hydration

A!!ition o) 3E'32 across a C/C

bon!


C C C C

3 '32

'3

' '

3

3

3 3

3

3

;'

3

3

3

5e

S

5e

'

3

3

3

'3+"37 '3+D5S


29/65

syn a!!ition

Anti+5ar(oni(o a!!itiono) F3G & F;3G


C ith ti


30/65

anti a!!ition

5ar(oni(o a!!itiono) F3G & F;3G

Co*pare -ith o=y*ercration+!e*ercration


3C 3

3g;Ac2

"37+32;

;3

C3

3

3g;Ac

%a'34

;3

C3

3

3

ti 5 ( i(


31/65

$=a*pleanti+5ar(oni(o

syn a!!ition

"his o=i!ation step occrs-ith retention of

conguration© 2014 by John Wiley & Sons, Inc. All rights resere!.

38C 3

'38+"373

C38

'32

3


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Marko"niko"

Anti)Marko"niko"



33/65

$ary of Alkene Hydrationethods&$ary of Methods for Con"erting Alkene toAlcohol

Reaction

Regiochemistr

y

Stereochemistr

y

Occurrence ofRearrangemen

tsAci!+cataly:e!hy!ration

5ar(oni(oa!!ition

%ot controlle! 7reent

;=y*ercration+

!e*ercration

5ar(oni(oa!!ition

%ot controlle! Sel!o*

3y!roboration+o=i!ation

Anti+5ar(oni(oa!!ition

StereospeciKc#syn a!!ition o)

E3 an! E;3

Sel!o*



34/65

. Electrophilic Addition of6roine ! Chlorine to Alkene

A!!ition o) E / Cl, 'r acrossa C/C bon!


'r2C C

'r

C C

'rCCl4

icinal

!ibro*i!e


35/65

$=a*ples


anti a!!ition o) 'r2

'r

'r

'r

'r

'r2

−?oC

race*ate

1

anti a!!ition o) Cl2

Cl2

−10oC2 h

hh

h

Cl

Cl

Cl

hh

Cl

sa*e as

rotation o) C1+C2 bon!

1

2

11A M h i f H l


36/65

11A. Mechanis of HalogenAddition

'rE'r bon!beco*es polari:e!-hen close to

al(ene

icinal!ibro*i!

e

bro*oni

*© 2014 by John Wiley & Sons, Inc. All rights resere!.

'r 'r

δ+

δ−

C C

'r

'r

C C 'r 'r

'r

'r

St h i t


37/65

Stereoche*istry Anti a!!ition


'r

'r

3 3 CCl4

'r 'r

3

'r

'r

3

S%2 reaction

anti

enantio*er


38/65

A!!ition o) bro*ine to cis+2+'tene

a b


C C3C

3

C3

3

'r

bro*oni*ion

achiral

δ+

δ−

C C

3C

3

C3

3

'r

'r

'r

C33C

C

3

'r

C3

(2R,3R)+2,+Dibro*ob&tane

chiral

a

'r

C 3

C3

C

3

'r

3C

(2S,3S)+2,+Dibro*obtanechiral

b

'r


39/65

A!!ition o) bro*ine to trans+2+'tene

a b


C C3C

3

3

C3

'r

bro*oni&*ion

achiral

δ+

δ−

C C

3C

3

3

C3

'r

'r

'r

C33C

C

C3

'r

3

(R,S)+2,+Dibro*ob&tane*eso

a

'r

C C383

C

3

'r

38C

(R,S)+2,8+Dibro*ob&tane*eso

b

'r


40/65

'. Halohydrin 8oration

A!!ition o) E;3 an! E / Cl, 'racross a C/C bon!

is the electrophile8ollos Marko"niko"#s r$le


2C C

;3C C

32;


41/65

5echanis*


38C 332;

'r 'r

'r38C 3

32;

;3

C3

3

'r


42/65

;ther ariation

I) 32; is replace! by 6;3, 6;3-ill be the ncleophile


;5e

'r

'r2

5e;3

e.g.

i l b d


43/65

/i"alent Carbon Copo$nds:arbenes

A. &tr$ct$re and Reactions of Methylene


C32 % % C32 % %heat

or light

Dia:o*ethane 5ethylenea carbene

%itrogen


44/65


R ti f ,th C b


45/65

Reactions of ,ther Carbenes: /ihalocarbenes

#C2 e.g. #CCl2

Leneration by α+eli*ination o)

chloro)or*


CCl2

3

CCl

Cl

Cl;t'& Cl t'&;3

Hsally a syn cis a!!ition across


46/65

Hsally a syn cis a!!ition acrossa C/C bon!


StereospeciKc reactions

3

3

Cl

Cl

a cyclopropane

t'&;M

C3Cl

ClCl

ClCl

CCl2

CCl2

+ Th &i & ith


47/65

+. The &ions)&ith

A stereospeciKc syn cis a!!ition

C32I2 NnC&

Ninc+copperco&ple

a carbenoi!

IC

32

NnI

0 , id ti f Alk


48/65

0. ,-idation of Alkenes:&yn 192)/ihydro-ylation

;erall# a!!ition o) 2 ;3 gropsacross a C/C bon!

6eagents# !ilte M5n;4 O 3;P O

32; O col! or ;s;4, pyri!ine then

%a3S;, 32;© 2014 by John Wiley & Sons, Inc. All rights resere!.

C C

;3 ;3

1+A M h i f &


49/65

1+A. Mechanis for &yn /ihydro-ylation of Alkenes



50/65

'oth reagents gie syn

!ihy!ro=ylation


C i ) th t t


51/65

Co*parison o) the t-o reagents

M5n;4# sally lo-er yiel! an!

possibly si!e pro!cts !e tooer+o=i!ation

;s;4# sally *ch higher yiel!

bt ;s;4 is e=tre*ely to=ic

o=i!atie cleaage o) C/C


;

;3

;3

;

1. M5n;4, ∆

2. 3

id ti Cl f Alk


52/65

-idati"e Clea"age of Alkenes

. Clea"age ith Hot 6asic 5otassi$ 5eranganate


;th l


53/65

;ther e=a*ples


A Clea"age ith ,*one


54/65

A. Clea"age ith ,*one

6Q

6

3

6

;6Q

6

;3

61. ;

2. Nn, Ac;3 or 5e2S

11. ;8

2. Nn, Ac;3

;

;

2 ;

3

;

1. ;8

2. 5e2S

5echanis*


55/65

5echanis*


C C

;;

;

C;

C

;;

C C

;;

;

initial o:oni!e

C

;

C

;;

; ;

C;

C

o:oni!e

ddition of Hydrogen Halides


56/65

ddition of Hydrogen Halideso Alkynes

6egioselectiity7ollo-s 5ar(oni(oBs rle


C C6 3

C C

3

6

3

3 / Cl, 'r, I

e=cess3

C C

'r

C3

'r

3

3

3

gem+!ibro*i!e

C C3C 33'r C C

C3

'r

3

3

3'r

5echanis*


57/65

5echanis*


C CC3 33 'r C C

3

3

C3'r

C C

C3

'r

3

3

C C

3

3

3C3

'r'rC

3

3

3

C

'r

C3

'r

3 'r

A ti


58/65

Anti+5ar(oni(o a!!ition o)hy!rogen bro*i!e to al(ynesoccrs -hen pero=i!es arepresent in the reaction *i=tre


3 'r

pero=i!es'r

3

E an! Z

R4

Ho to 5lan a &ynthesis:


59/65

. Ho to 5lan a &ynthesis:&oe Approaches ! E-aples

In planning a synthesis -e o)tenhae to consi!er )or interrelate!

aspects#1. Constrction o) the carbon

s(eleton

2. 7nctional gropinterconersions

. Control o) regioche*istry

4. Control o) stereoche*istr© 2014 by John Wiley & Sons, Inc. All rights resere!.

4A Retrosynthetic Analysis


60/65

3o- to synthesi:e

6etrosynthetic analysis

4A. Retrosynthetic Analysis


;3

target *olec&le prec&rsor

;3


61/65

Synthesis

5ar(oni(o a!!ition

o) 32;


3o- to synthesi:e ;3


63/65

;ne approach to retrosyntheticanalysis is to consi!er aretrosynthetic step as aF!isconnectionG o) one o) thebon!s

In general, -e call the )rag*entso) a hypothetical retrosynthetic

!isconnection &ynthons

. /isconnections9 &ynthons9 and &ynthetic E>$i"alents


$=a*ple


65/65


!isconnection

synthons

synthetic eialent

C38hii h C3

h %a3C I

Documents

Chapter 8 Lecture - Organic Chemistry (11 Ed.) by Solomons