Class notes
SN2 Reaction Mechanism - Organic Chemistry
- Course
- CHEM 281 (CHEM281)
- Institution
- Simon Fraser University (SFU )
Condensed class notes for lectures about the Substitution Nucleophilic SN2 reaction mechanism.
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SU2 MECHANISM : This REACTION involves ANucleophile
Attacking Electrophie
An And BATE : THE RATE FOR THIS TYPE Of REACTION DEPENDS BOTH ON THE
RATE = K NU- ELECTROPHiLE
THE SNZ REACTION MECANIM PROCEEDs Concentration of THE NucleopHrEd THE CONCENTRATron of
LEAGGroup GETag REPLACED
1 .
m
Bowd formAron THE ELECTROPARE
Breakage
↳ THES MEANS THAT All a
SangLE
.
CONCERTED Step .
Occurs
SMULTANEOUSCY . In OrdER for THES TO BE TRUE ,
The REACTION Must HAVE A
TRANSMRON STATE .
CONONIONS FOR REACTION
#
It
IMPORTANT FACTOR
DETERMING
HO Br
THE NECLEOPHRE -
THE ABUSY OF THE MOREOPARE TO DOMRE ELECTRONS IS THE MOST N SUZRASE
Hz-o
>
HJC-Br Ho Br
.....
......... - ·
TRANSTRON STATE : DONERS
a)
CHARGE NEGANEL CHARGED
BASES HAVE MORE ELECTRONS AVAILABLE THAN THER AIDS THIS MARES THEM BETTER
CONJUGHE
: . .
OF BONDS
addrowsy formarow of NOTERMEdRACE HAS
HIGH ENERGY
THE
BREAKING CHARGED
THE TRANSPROW STATE S A WHICH A
Energy
ARE A Ac t i o n
LARGER
TEMPORARY STATE NO ,
b)
FORMG
And THE TRANSOW STATE CANNOT BE SCHATED, ASM IS A STABLE OR DISTINET SPECTES RESONANTE : DELOCALTED ACROSS MULTIPLE ATOMS WILL IMPATR THER REACTNMY SMOCE THE SPECIES US MORE STABLE
CHARGES
NOT . V .
HAS REAL LIFETIME , As Bowd BRATron C) SoLVATION : THE REACTION WILL BE HIVERED If THE NUCLEOpHrE iS SONABLE POLAR APROTC SOLVENTS ARE USED TO Avoid THIS PROBLEM
Lasting Long
no -
As A . . .
6) ICEPRES and
GOMETRICALy Demanding
STErres :
BukrERIverEoptMES Are WEARER SLOW THE REACTION . SuZ IS A REACTrow .
1 No- STEREOCHEMISTRY :
PROR TO THE MUCLEOPHILIC ATTACK , THE
Add MONALly THE Number Of SUBSTMENTS Al THE L CARBON WIL infLUENCE RATE THE EASTERN is for THE NUCLEOpHHE
s
, . To
La
·
It
ELECTROPHML MOLECUE POSSESSES A TETRAHEORAL GEOMETRY - ACCESS THE ELECTROPANIC CENTRE, THE FASTER THE REACTION Occurs .
I
LG
......... HOWEVER TEMPORARY ADOPTS
2 nw
"It DURING
THE TRANSMON STATE, M A
It"
,
Suz
only
ME Hzc-Br THE OF THE
LEAGGROUp
Bipyramidas fasT
LEAGABRIT LEAGGROUP
GEOMETRY With THE : THE ALSO DETERMINES THE
Tergone New-leavinggroup
,
Hz
·
316
> -
FORCES FROM
10 Asc Br
Wit THE LANDER WAALS REACTION RATE
TOGETHER
SUSSTVENS in A PLANE . .
THE MeLeopre puSHES And
20 A i
r
a) STABHMY : THE BEST ARE ONES THAT ARE STABLE ANTOWS ONE
The SUBSTrEns
Away Auror
Now-LEarng HsC ,
CH3
Br
V
S Low
LEARNYGROUPS
30 Hac su 1 only
THE FORMS A TETRAHERAL M LOOKS Like An THEY HAVE LEfT THIS ENSURES THAT THE MECHANISM
THERMODYNAMICALLY FAROURED
AGAN
AS THE
LEAVINGGROUP
MOLECURE DEPARTS . . IS .
STEREOCHEMISTRY At THAT CENTRE b) The Same factors That Make
Marengoodering
THIS INVERTS THE OVERALL
INVERTED UMBRELLA .
Basicry : A Wear Base also
I Br ci
good LEAggroups
for
Halogens Learnggroup orusy
Make SUBSTHMON REACTIONS
group
.
HI HBr HCl
Strongestacids
<merkest And
WHAMSON ETHER
SYNTHESTS : AN SUZ REACTION
Sn2 REACTIONS
BETWEEN AN ALKOVdE & AlkyL HALidE form poor
impromy Earuggroups
TO An :
ETHER TWO
STEP REACTION OH is A Terrible Base
Learnygroup STrough
1 is Too
Stands for SUBSTroon NoteopAric
, , .
SNZ
.
BioLECr-
CAN BE RETROSYNTHETIC (REVERSERAN) or Forward
. We crow from said SuformE ESTERs
CANALYSIS
usmoy
Or .
THE FAVOURED REACTION HAS 1
. Acid-Base Catalysts : Acid Catalysis Altrates THE ELECTROpHMEI THE REACTION WHE BASE CATALYSIS ACTIVATES THE
REACTME PRODUCTS/ 1) Acid Catalysis
signficantly
THE MORE of H20 Whic Better
mereophre in The reaction
leaminggroup
Hz is used to Tur n moto a .
+ Nat
- .
0
REACTANTS for RETROSYNTHETre . Sur for Esters
2 : & morecute
Using
sat
8 +
Forward RESPECTTEly
-
↓ 2) + THAT HAS A ELECTROw -
Strong writing +-Br
Ho
Oz H> Br
Br >
OH HzC, + But +
. -
>
o O
HC
attached create a
Group oxygen
To to
VUCLEOPARES & CARBON- CARBON BONDS : WEARER BASE A THUS A BETTER
LEANGGroup
.
⑧
~
3 -
Acetyldes Super Helpfu for Carbon-CARBON Bonds A Suz REACTre SUFONAE 1) Of > a
Creamy Leaggroups
Arrows Are Excellent Due
-
Cyanides THAI BECAUSE
THEY ARE SUCH VECLEOPAUES RESONANCE of THE
STRONG
S TO Some common
Oxygens
.
.
Sur forATES ARE 2) Br +
0 7 Br + o , -
,
-
↳
·
Tosyle (ots) 0 - -Us11
ken
H R
↓ !
~
Br ACETONARME
7
chorage
O
P · II
·
(OMs) TRifLATE (oTf)
MESYLATE ·
as O S
Cfz
- -
R ! r !
1) varHz
Hd Ch
BrHE as
=
, -
-
Hechwa -
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