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Topic: Nucleophilic Substitution  (Read 12292 times)

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Offline english

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Re: Nucleophilic Substitution
« Reply #15 on: February 09, 2007, 11:02:48 PM »
A poor nucleophile cannot sufficiently displace the leaving group.  The leaving group dissociates...via an SN1 mechanism.  A carbocation intermediate will be formed...of which possible rearrangements can occur, as you mentioned...which entails you are referring to an SN1 mechanism.

Offline deutdeut

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Re: Nucleophilic Substitution
« Reply #16 on: February 09, 2007, 11:04:08 PM »
Not all nucleophiles are bases, why? Isn't they are all Lewis bases as they act as electron donor to form covalent bond?

Offline english

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Re: Nucleophilic Substitution
« Reply #17 on: February 09, 2007, 11:07:41 PM »
Not all nucleophiles are bases, why? Isn't they are all Lewis bases as they act as electron donor to form covalent bond?

Lewis bases, yes.  We mean Bronsted-Lowry bases.  An alcohol can be a nucleophile...it is a Bronsted-Lowry acid, but a Lewis base.

Offline enahs

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Re: Nucleophilic Substitution
« Reply #18 on: February 09, 2007, 11:10:05 PM »
A poor nucleophile cannot sufficiently displace the leaving group.  The leaving group dissociates...via an SN1 mechanism.  A carbocation intermediate will be formed...of which possible rearrangements can occur, as you mentioned...which entails you are referring to an SN1 mechanism.

In a secondary substrate elimination (E2) is favored by a strong base due to steric hindrance.

Offline deutdeut

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Re: Nucleophilic Substitution
« Reply #19 on: February 09, 2007, 11:12:07 PM »
So we are mentioning the bases are strong or weak, it just depends on how well they share electrons with a proton? (by Lewis base definition)  And Mr. k.v. , when using weak nucleophile with a secondary halide, say , if water or alcohols reacts with secondary halides, hydrolysis occurs,  which mechanisms, SN1 or E dominates?
« Last Edit: February 09, 2007, 11:45:51 PM by deutdeut »

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