nucleophile q

[SunnyD0119]

Advertisement - Members don't see this ad

how the heck do you figure out if something is a good nucleophile
i know in protic solvents a bigger atom is a better nucleophile
its the opposite for aprotic
but how do you figure itout i just memorized and i would ilke to know the steps to figuring out good nucleophiles and leaving groups

 

[dat_student]

how the heck do you figure out if something is a good nucleophile
i know in protic solvents a bigger atom is a better nucleophile
its the opposite for aprotic
but how do you figure itout i just memorized and i would ilke to know the steps to figuring out good nucleophiles and leaving groups

I don't think "size" has anything to do with it but you can use the size to memorize some exceptions. In general, nuceophilicity parallels basicity: stronger bases are better nucleophiles.

 

[Divineimpetus]

how the heck do you figure out if something is a good nucleophile
i know in protic solvents a bigger atom is a better nucleophile
its the opposite for aprotic
but how do you figure itout i just memorized and i would ilke to know the steps to figuring out good nucleophiles and leaving groups

big nucleophile (bulky) = E2

not so bulky nucleophile, want aprotic solvent = Sn2

when you see nucleophile think base


I would suggest reviewing the chapter on Sn1, Sn2, E1, E2 reactions in your organic chemistry textbook to get a better understanding...especially since these reactions are the foundation of all organic chemistry reactions.

 

[mochafreak]

I don't think "size" has anything to do with it but you can use the size to memorize some exceptions. In general, nuceophilicity parallels basicity: stronger bases are better nucleophiles.

Going across a period as electronegativity increases nucleophilicity parallels basicity, but as far as groups go, size does matter. Iodine is larger than flourine and a stronger nucleophile. Flourine is more basic than iodine, because it's more electronegative. Basicity is about thermo (how stable a negative charge is) and nucleophilicity is about kinetics. Larger atoms can polarize their electron density (it moves so their more attracted to a positive dipole), so they are drawn to an electrophile faster than a smaller atom that can't move its electron density.

Everyone's been asking a lot about determining basicity, acidity, nucleophilicity, etc. If you want to thoroughly understand the basics of Ochem (acidity, SN1, etc.) you should get a copy of "Organic Chemistry as A Second Language" by Klein. It's a quick read and I'm guessing a great reference for the type of basic ochem that's on the DAT. Of course, I haven't taken the DAT yet, but, I don't think you'll be dissappointed with the book. 😉

 

[dat_student]

Going across a period as electronegativity increases nucleophilicity parallels basicity, but as far as groups go, size does matter. Iodine is larger than flourine and a stronger nucleophile. Flourine is more basic than iodine, because it's more electronegative. Basicity is about thermo (how stable a negative charge is) and nucleophilicity is about kinetics. Larger atoms can polarize their electron density (it moves so their more attracted to a positive dipole), so they are drawn to an electrophile faster than a smaller atom that can't move its electron density.

like i said, there are some exceptions & group 7 is an exception. Usually, nucleophilicity parallels basicity.