what is difference between strong base and nucleophile??

[smile101]

i m confused on nucleophiles and bases!!!
I know strong nucleophiles make strong bases, but what if they have a list of compounds and ask me to pick the strongest base or nucleophile...I know dr. romano is trying to give some examples of them...but I am just confused

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[TheWiredNerv]

Take some steps back.
What is the definition of a nucleophile?
What is a definition of a base?

 

[smile101]

Take some steps back.
What is the definition of a nucleophile?
What is a definition of a base?

thanks..i think i have it figured out through this link here: http://www.cem.msu.edu/~parrill/nucleophile.html

 

[scuzfly]

Take some steps back.
What is the definition of a nucleophile?
What is a definition of a base?

Aren't they the same in a way? Nucleophiles donate electron pairs while bases accept protons correct? Acids don't accept protons they donate them (HCl) so if you accept a proton aren't you donating a pair of electrons?

 

[Orgodox]

Aren't they the same in a way? Nucleophiles donate electron pairs while bases accept protons correct? Acids don't accept protons they donate them (HCl) so if you accept a proton aren't you donating a pair of electrons?

Most def not!! Look at the outcome. A base would take a proton off of a compound and a nucleophile would attack and now be attached to it. 2 very different things.

 

[klutzy1987]

Most def not!! Look at the outcome. A base would take a proton off of a compound and a nucleophile would attack and now be attached to it. 2 very different things.

Not necessarly, OH- is a strong nucleophile but it will for pull off a hydrogen to form water and usually not attach. A strong nucleophile can be a strong base.

 

[Orgodox]

Im not saying that one thing cant act as both at different times. Many things not just OH can act as a base OR nucleophile. They are not exclusiv many times a strong base is a strong nucleophile as you point out. I was responding to the comment that "whats the difference between a nucleophile and a base they have same outcome" question. To which I repeat they are VERY DIFFERENT OUTCOMES if it acts as a base or a nucleophile.

 

[klutzy1987]

Im not saying that one thing cant act as both at different times. Many things not just OH can act as a base OR nucleophile. They are not exclusiv many times a strong base is a strong nucleophile as you point out. I was responding to the comment that "whats the difference between a nucleophile and a base they have same outcome" question. To which I repeat they are VERY DIFFERENT OUTCOMES if it acts as a base or a nucleophile.

Oh ok then i agree with you.

 

[Orgodox]

Thanks klutzy didnt mean to be ambiguous on previous post thought i was clear.

 

[scuzfly]

so the difference is the outcome. The nuc will attach itself while the base takes a proton. Is that the MAJOR difference in the outcomes? I knew that part but I thought there might be more to it than just the outcomes. I guess a base wouldn't be capable of an SN1 SN2 rxn.

 

[Orgodox]

Of course there is more to it than that (mechanistically there are different transition states....) but its the most obvious and BIGGEST difference especially at face value which was in response to your question arent they same.
Of course a base acting as a base cant be Sn1 or Sn2 because that by definition that doesnt sense. S stand for substitution and a base isnt substituting because it takes the proton. There are however base reactions that have similarities to sn1 sn2 namely the E1 and E2 and they compete.