ester formation

[andyjl]

On pg 377 of kaplan, it says the carboxylic acids react with alcohols under acidic conditions to form esters and water. In the acidic solution, the O on the carbonyl functionality will get protonated which accentuates the polarity of the bond putting more positive charge on the C. I am wondering how protonating the oxygen makes the C more positive.

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[chreesteene]

When you protonate the oxygen of a carbonyl, this gives that oxygen three bonds and one lone pair, making the carbonyl oxygen positively charged.

Through resonance, the carbonyl double bond donates an electron pair to the now protonated oxygen. Now the carbonyl oxygen has two bonds and two lone pairs, and is neutral. The carbonyl carbon now has three bonds and is positive, thus making it more electrophilic for attack by a nucleophile (alcohol).

>C=O-H becomes >C-O-H


Hope that helps!

 

[andyjl]

yes that does help. thank you