E2 and SN2 clarification needed please

[KiTmAn]

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E2 is favored over SN2 with strong bases(strong nucleophiles)..rite?

 

[QofQuimica]

E2 is favored over SN2 with strong bases(strong nucleophiles)..rite?

That is often true, although if your substrate (alkyl halide) is primary, you will probably get mostly SN2 product, unless your base is bulky. Two things should immediately tip you off that a reaction goes by E2: one is a strong, bulky base like t-butoxide or LDA (lithium diisopropylamine), and the other is the heat symbol, which looks like a triangle (it's the greek letter delta). Heat tends to favor eliminations over substitutions in general. If the substrate is secondary and you mix it with a strong base, you may still get some SN2 product, but E2 will probably predominate. And if it's tertiary, E2 is the only possibility.

 

[KiTmAn]

thnx ...ill remember that for sure

 

[LabMonster]

That is often true, although if your substrate (alkyl halide) is primary, you will probably get mostly SN2 product, unless your base is bulky. Two things should immediately tip you off that a reaction goes by E2: one is a strong, bulky base like t-butoxide or LDA (lithium diisopropylamine), and the other is the heat symbol, which looks like a triangle (it's the greek letter delta). Heat tends to favor eliminations over substitutions in general. If the substrate is secondary and you mix it with a strong base, you may still get some SN2 product, but E2 will probably predominate. And if it's tertiary, E2 is the only possibility.

Beautiful Q!

 

[MDTDO]

E2 is favored over SN2 with strong bases(strong nucleophiles)..rite?

NaI in Acetone = Strong Nucleophile in polar aprotic solvent: SN2 only.. I've seen that one a lot, its an example of a strong nucleophile that isnt really a strong base. Plus, the aprotic solvent is a giveaway. Thats the only time other than what Q said about tertiary substrates where they dont compete.
When I took o-chem I always looked first at the solvent, I dont know how strongly the MCAT is gonna test that though

 

[riceman04]

E2 is favored over SN2 with strong bases(strong nucleophiles)..rite?

And are bulky!
reason being is that these big ass bases will sterically compete with SN2 and thereby prevent SN2 from occuring