Sn1 Sn2 E1 E2????????

[WantsThisBad]

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Has anyone thought of a clever way to memorize conditions to predict if a reaction will run Sn1 Sn2 E1 or E2? Thanks in advance!😱

 

[BIGNE]

http://pages.towson.edu/ryzhkov/handouts/SEhand.html

best link ever for this stuff. I loved orgo 🙂

 

[scott8013]

i don't know how clever it is but here's how i do it:

E2 and SN2 are both dependent upon the rate of the base/nucleophile hence the 2 (for second order kinetics I think). So a strong base/nucleophile is indicative of E2 or Sn2.

Weak base and nuc. is Sn1 or E1.

#2 is a backside attack - (like having to go to the bathroom number 2 is an attack of the backside) so, a strong but bulky base cannot make the backside attack due to steric hindrance so you have only E2.

generally any base with a negative charge is going to be 2nd order - so then you just have to watch for the bulky ones like tertbutyloxide to determine if it is a mixture of SN2 and E2 or just E2.

other than that i don't know any good tricks - just memorize the substrates/alkyl halide types and which reaction can take place then apply the rules above about strength of base/nucleophile and you should be in business.

hope it helps.

 

[littlealex]

-edited-
I didn't read the question. My response was ******ed and thus removed.

 

[WantsThisBad]

Thanks guys.

 

[BlackSails]

You cant predict if a given reaction will procede, espically for Sn2 and E2. For those, you really have to look at the structures.

 

[161927]

STRONG BASE, OR STRONG NUCLEOPHILE? OR HIGH TEMPERATURE?

E2, Sn2



"MILD" CONDITIONS
Low temperature --> Sn1
Weak nucleophile --> Sn1
Weakly basic solvent (Ethanol) --> Sn1
Polar protic solvent (to stabilize carbocation) --> Sn1


SUBSTRATE CONDITIONS
3o = Sn1
1o = Sn2

2o = either

exception: Allylic/benzylic/resonance-stabilized carbocation = Sn1