neighbouring group

consider 3 reactions
hydrolysis of EtSCH2CH2Cl , EtNCH2CH2Cl , EtOCH2CH2Cl
Arrange them in increasing order oh reactivity, where N , O , S act as neighbouring group......

19 Answers

1
skygirl ·

but your ans is wrong isnt it ?

1
voldy ·

no . sky go through Sykes . it has it. even though not fully I think . this should do a whole lot of good , I think .and it's not extra. it's one of the needed concepts.

http://en.wikipedia.org/wiki/Neighbouring_group_participation. this should be good enough :)

1
skygirl ·

DUN BOTHER TO KNOW!
IT IS NOT IN THE SYLLABUS!
LEAST INTERESTED TO KNOW EXTRA THINGS IN CHEM ...
SORRY :(

1
greatvishal swami ·

@ sky
i told about it in 1 of the posts above
its strange dat u dont know it!!!!

1
skygirl ·

i dunno wat is that anchimeric assistance... may be same as intramolecular substituition..

1
greatvishal swami ·

wat intramolecular substitution???!!!!
its anchimeric asistance which means SN2 twice
@shrinath
if u are talking about ease of donating elec to form 3 member ring then u r right
bt then larger size of S willalways afct rate of SN2

1
skygirl ·

yes me wrong...
its intramolecular substiturtion...
wat srinath told is correct...

1
voldy ·

the ans is 1>2>3 . Nitrogen is a better donor than O .right?????

then b/w O and S . S is better. fine????? . then b/w N and S . S is obvious as it has two lone pairs ans also it's e.n is less. .

1
skygirl ·

ok no comments :P
i have weird knowledge in chem..
wont debate on a topic on which i am leeeaaast confident :P

1
greatvishal swami ·

but is anythng wrong in my view
& anyways i never easily consider the given ans as correct

1
greatvishal swami ·

3>2>1

for 3&2 its obvious as 2p-2p orbitals hav gud overlap

thnk more if ans is correct

1
greatvishal swami ·

how come S has no lone pair

sky r u getting the word neburing gp???? apply anchimeric assistance
lone pairs of S,O,N will first force Cl- out by SN2 by making a 3 member cyclic ring
then again attaking nucleophile will substitute through SN2 mechanism
S being bigger in size will inhibit SN2 a bit hence i gave 3>2>1 as ans

1
skygirl ·

the H2O molecule(nucleophile) will attack at the most electrophilic site...

now compare which is more electrophilic site...

S has no lone pairs... so most electrophilic center..

O is very electronegative but has lone pairs...

N is less electrophilic than O and also has lone pairs...

(O has two lone pairs n N has only one but O is far more electronegative than N...)

i thnk this is a correct way to think.. if some chem expert assures me...
correct me, if wrong..

1
voldy ·

explanation .go through Peter Sykes.

It's the ability of the atom to donate electrons , that matters not by inductive effect , I feel .
again for mechanism and better understanding . go to Peter Sykes.

1
greatvishal swami ·

@sankar where r u applying in ductive effect
in 3&2 or all 3

3
msp ·

the order is 1>3>2
because of inductive effect

1
big looser ......... ·

ya sky you r write,, can u explain

1
skygirl ·

is it 1 > 3 >2 ??

1
big looser ......... ·

wrong dude.......... i know that 1st reacts 104 times faster than 3rd. but i have confusion with second.... check your ans....

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