this might be easy for you guys, but its something i dont understand...

[abcxyz0123]

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I was just wondering, when you are in the process of figuring out whether a reaction will go to sn1, sn2, e1, or e2, how do you figure out whether the base/nucleophile is a strong base or a weak base, if you are not familiar with it and don't have a reference table to show you? I know that HO- and H- are strong bases, while acetone is a weak base, but are you expected to memorize the entire table of strong and weak bases in order to do these types of problems...or is there some sort of conceptual trick where you can figure out how strong the compound is just by looking at its structure or something? Also, where, in the middle of the table, do you draw the line between which base is "strong" and which base is "weak" when you are looking at a table of bases listed by their strength? I understand everything but this so far, and its bugging me a lot. if you could help me out, i'd appreciate it a lot.

 

[Medbound786]

In order to gauge the strength of a base, you should look at the stability of its conjugate acid.......Lets a take particular Base, B.......now, add a proton H+ to it (since bases donate e- and accept H+) to give BH+.........now, decide whether this resulting species (BH+) is more stable than the orginal species (B).......If yes, then, the base is a strong one and if not, it is a weak one. I hope I made sense somewhere in there

It is DEFINATELY useful (at least for me it is) to know as much as possible which acids and bases are strong and weak from the charts. Memorize the most commonly used acids and bases.

 

[gdbaby]

Ditto

 

[abcxyz0123]

In order to gauge the strength of a base, you should look at the stability of its conjugate acid.......Lets a take particular Base, B.......now, add a proton H+ to it (since bases accept e- or H+) to give BH+.........now, decide whether this resulting species (BH+) is more stable than the orginal species (B).......If yes, then, the base is a strong one and if not, it is a weak one.
I hope I made sense somewhere in there

It is DEFINATELY useful (at least for me it is) to know as much as possible which acids and bases are strong and weak from the charts. Memorize the most commonly used acids and bases.

but how do you judge, in that last step, whether the resulting species is more stable than the original species? it makes sense but i feel like i'm missing something...

 

[Medbound786]

but how do you judge, in that last step, whether the resulting species is more stable than the original species? it makes sense but i feel like i'm missing something...

Well, the stability of the resulting species, BH+ varies from the orginal base to base. For instances, bases that have lone pair electrons OR have overall negative charges readily accept H+ protons since the resulting product BH+ is electronically more stable. Therefore such bases may be relatively stronger than others. Hope that helps