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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: xshadow on April 11, 2020, 11:27:39 AM

Title: acetolysis reaction
Post by: xshadow on April 11, 2020, 11:27:39 AM

In an acetolysis reaction which is the nucleophilic compound?

CH₃COO^- (which gives Sn2)
or
CH₃COOH (which usually gives Sn1)


thanks

Title: Re: acetolysis reaction
Post by: hollytara on April 12, 2020, 11:41:49 AM

I don't think it is that simple...

If you have a tertiary substrate it will give SN1 no matter what the nucleophile..

Is it just in acetic acid, or is there also an acetate salt added?  In pure acetic acid, the autoionization constant is 3.5 x 10-15, so there is 6 x 10-8 M acetate ions in pure acetic acid which is pretty low.  So in pure acetic acid, acetic acid might be the nucleophile, but with some added acetate it is likely to be acetate ion. 

What is the temperature?  Refluxing acetic acid? 

The classical physical organic chemists (Bartlett, Winstein, Olah, etc) undoubtedly answered all these questions as they argued about the norbornyl cation and so forth.

Title: Re: acetolysis reaction
Post by: xshadow on April 13, 2020, 10:46:58 AM

Quote from: hollytara on April 12, 2020, 11:41:49 AM

I don't think it is that simple...

If you have a tertiary substrate it will give SN1 no matter what the nucleophile..

Is it just in acetic acid, or is there also an acetate salt added?  In pure acetic acid, the autoionization constant is 3.5 x 10-15, so there is 6 x 10-8 M acetate ions in pure acetic acid which is pretty low.  So in pure acetic acid, acetic acid might be the nucleophile, but with some added acetate it is likely to be acetate ion. 

What is the temperature?  Refluxing acetic acid? 

The classical physical organic chemists (Bartlett, Winstein, Olah, etc) undoubtedly answered all these questions as they argued about the norbornyl cation and so forth.

Was an exxercise


Says only acetolysis witch CH3COOH (pure,not salt)
Here I could say that the nucleophile is  the acetic acid (so Sn1 usually)


While if I have acetic acid as a solvent but also a concentrated  salt of CH₃COO^- this should be  a Sn2

Negative charged nucleophile

Is it correct?thanks

Title: Re: acetolysis reaction
Post by: hollytara on April 13, 2020, 12:12:58 PM

BP of acetic acid is 120 C. 

This is a little low to drive SN1 of primary substrates....  but SN1 likely for secondary and tertiary. 

Adding the salt will push to SN2 for secondary as well.  Tertiary only SN1 no matter what. 

Title: Re: acetolysis reaction
Post by: HollySCH on April 14, 2020, 08:25:55 AM

If you see a charged nucleophile/base, you can rule out carbocation formation (i.e. rule out SN1/E1). In other words, the reaction will be SN2/E2.