Carboxylation of sodium phenolate

[espen180]

Homework Statement

Predict the products and reaction mechanism when sodium phenolate reacts with carbon doixide, then acid.

Homework Equations

Sodium phenolate: Ph-ONa
Carbon Dioxide: O=C=O

The Attempt at a Solution

The carbon atom in CO₂ has a positive partial charge, so I expect an electrophilic aromatic substitution mechanism. The hydrogen which is released will protonate one of the oxygen atoms and make a carboxy group. The result is a carboxylation of the original compound. The -ONa group is electron withdrawing, so only the orto and para positions are susceptible. Then, the acid will remove the sodium and protonate the oxygen to form an alcohol group.

The products will then be orto-hydroxybenzoic acid, or 2-hydroxybenzoic acid, and para-hydroxybenzoic acid, or 4-hydroxybenzoic acid. I expect roughly 66% orto and 33% para among the products.

 

[sjb-2812]

Homework Statement

Predict the products and reaction mechanism when sodium benzoate reacts with carbon doixide, then acid.

Homework Equations

Sodium benzoate: Ph-ONa
Carbon Dioxide: O=C=O

The Attempt at a Solution

The carbon atom in CO₂ has a positive partial charge, so I expect an electrophilic aromatic substitution mechanism. The hydrogen which is released will protonate one of the oxygen atoms and make a carboxy group. The result is a carboxylation of the original compound. The -ONa group is electron withdrawing, so only the orto and para positions are susceptible. Then, the acid will remove the sodium and protonate the oxygen to form an alcohol group.

The products will then be orto-hydroxybenzoic acid, or 2-hydroxybenzoic acid, and para-hydroxybenzoic acid, or 4-hydroxybenzoic acid. I expect roughly 66% orto and 33% para among the products.

2 things spring to mind, 1) PhONa is not sodium benzoate. 2) are you sure about your directive effects?

 

[espen180]

1) A mistake on my part. The problem gave the structure, not the name. It should be sodium phenolate. I'll correct the opening post.

2) About the regiochemistry, my thinking is that since the hydroxy group is orto/para-directive, then a -ONa group should be so too, even more so, since the electronegativity of Na is less than that of H, meaning more electron density near the oxygen.

 

[sjb-2812]

1) A mistake on my part. The problem gave the structure, not the name. It should be sodium phenolate. I'll correct the opening post.

2) About the regiochemistry, my thinking is that since the hydroxy group is orto/para-directive, then a -ONa group should be so too, even more so, since the electronegativity of Na is less than that of H, meaning more electron density near the oxygen.

Fair enough. My point two was based on the structure being benzoate, rather than phenolate. You may also want to, if you still can, amend the title of the thread as well :)

 

[Borek]

You may also want to, if you still can, amend the title of the thread as well :)

Espen can't