SN2/E2 reaction question

[artsyme]

I'm a little confused about this...

I thought SN2 reactions take place in aprotic polar solvents. In the Kaplan book it says that nucleophilic strength in aprotic solvents works like basicity, so that the STRONGER the base, the stronger the nucleophile ( F>Br>Cl>I).
However, reading about the competition between SN2 vs. E2 reactions, it says that E2 favors a strong base (to remove a proton), while SN2 favors a WEAK base to serve as a good nucleophile......

do SN2 reactions work better using strong or weak bases as nucleophiles????

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[thefifthbeatle]

All I know is that SN2 is only one step, so it needs a strong base to make it one step.

 

[hoak]

Strong nucleophile is not necessary strong base. Sn2 reaction will favor strong nucleophile (attack Carbon) while E2 will favor strong base (attack H).

 

[darksky]

I'm a little confused about this...

I thought SN2 reactions take place in aprotic polar solvents. In the Kaplan book it says that nucleophilic strength in aprotic solvents works like basicity, so that the STRONGER the base, the stronger the nucleophile ( F>Br>Cl>I).
However, reading about the competition between SN2 vs. E2 reactions, it says that E2 favors a strong base (to remove a proton), while SN2 favors a WEAK base to serve as a good nucleophile......

do SN2 reactions work better using strong or weak bases as nucleophiles????

Base: charges moving from here to there.

Nucleophile : atoms banging into other atoms. Chemistry people use the word ‘attack’ for a nucleophile. They never say the base ‘attack’.

If the reagent bangs into the substrate to initiate a reation, then the reagent works like a nuleophile.

If the reagent rip off proton from another atom, then the reagent works like a base.

Sn2 atoms (nucleophile) bang into other atoms or molecules at the right location so hard so that a reaction happens. So you need a strong nucleophile.

E2 the rip off artist steals proton from another atom to initiate a reation.