Chemistry MCQ thread...

[Xthegreat]

.

ans is D.

Sn1 is undergone by tertiary haloalkane
Sn2 is undergone by primary and secondary haloalkanes

- Sn1 and Sn2 are reaction mechanism
- when tertiary undergo substitution, the halogen has to break off first before the new nucleophile can fit in
- so it's like one by one, break then form so it's Sn1
- when primary and secondary undergo substitution, before the halogen break, the nucleophile has already form a partial bond with the C
- so at the intermediate stage, C is bonded to 5 groups
- so it's call Sn2

ok?

 

[xHazeMx]

.

D...tertiary .... the CI almost looks like chlorine

correct

 

[RafaySid]

I know the answer is D, but is it a hard-and-fast rule that ONLY tertiary alkyl halides undergo Sn1? It's written on WIkipedia that normally secondary and tertiary undergo.. Can anyone explain this..?

 

[Octahedral]

I tried uploading the snapshot but it says the extension bmp is not allowed???? :%)

 

[hassam]

zISHii...come'on i posted a tuff one for u

 

[histephenson007]

I know the answer is D, but is it a hard-and-fast rule that ONLY tertiary alkyl halides undergo Sn1? It's written on WIkipedia that normally secondary and tertiary undergo.. Can anyone explain this..?

I remember reading from a textbook that secondary undergo a mixture of Sn1 and Sn2 mechanism.
so...

primary ....... Sn2 mechanism
secondary ..... mixture of Sn1 & Sn2 mechanisms
tertiary ........ Sn1 mechanism

 

[sweetiepie]

DOES ANYONE HAS PAPERS B4 2002 PLZZ IF U HAV CAN U SEND MEE......

 

[histephenson007]

@hassam

is it C?

 

[histephenson007]

DOES ANYONE HAS PAPERS B4 2002 PLZZ IF U HAV CAN U SEND MEE......

There was a topic few days ago where someone posted papers of 2000, u can search for it in other topics... it will probably be a few pages after this thread.

 

[Saturation]

.

ans is D.

Sn1 is undergone by tertiary haloalkane
Sn2 is undergone by primary and secondary haloalkanes

- Sn1 and Sn2 are reaction mechanism
- when tertiary undergo substitution, the halogen has to break off first before the new nucleophile can fit in
- so it's like one by one, break then form so it's Sn1
- when primary and secondary undergo substitution, before the halogen break, the nucleophile has already form a partial bond with the C
- so at the intermediate stage, C is bonded to 5 groups
- so it's call Sn2

ok?

Ok, but isn't SN1 (tertiary) the one with the intermediate?
http://en.wikipedia.org/wiki/SN1_reaction

 

[sweetiepie]

m not getting it...

 

[xHazeMx]

.

ans is D.

Sn1 is undergone by tertiary haloalkane
Sn2 is undergone by primary and secondary haloalkanes

- Sn1 and Sn2 are reaction mechanism
- when tertiary undergo substitution, the halogen has to break off first before the new nucleophile can fit in
- so it's like one by one, break then form so it's Sn1
- when primary and secondary undergo substitution, before the halogen break, the nucleophile has already form a partial bond with the C
- so at the intermediate stage, C is bonded to 5 groups
- so it's call Sn2

ok?

Thanks alot ! i had some confusion in this part

 

[hassam]

well shud i tell......wait 5 min..then i ll post ans. with expl

 

[xHazeMx]

zISHii...come'on i posted a tuff one for u

It's B

 

[xHazeMx]

I tried uploading the snapshot but it says the extension bmp is not allowed???? :%)

save it with the extension (.png)

 

[Aloo007]

@ hassam
I think its B 1 and 2

 

[Xthegreat]

both Sn1 and Sn2 have intermediates
its just that the Sn2's intermediate is a very fast step such that it is often ignored.

 

[Saturation]

zISHii...come'on i posted a tuff one for u

C right??

 

[Saturation]

both Sn1 and Sn2 have intermediates
its just that the Sn2's intermediate is a very fast step such that it is often ignored.

aha, so if they ask which one has intermediate steps (like in a 1,2,3 question) , is it yes for SN2??

 

[diwash]

@ hassam...B right?