How do you draw the mechanism (with curly arrows) for the reaction of methanol and benzoic acid?

(Acid catalysed with H2SO4 to form methyl benzoate and H2O)


Also, are the ratios of methanol to ester and Benzoic acid to ester both 1:1? ThanksHow do you draw the mechanism (with curly arrows) for the reaction of methanol and benzoic acid?
Not possible to draw them in text, other than to describe in words.


The overall equation is





C6H5COOH + CH3OH ---%26gt; C6H5COOCH3 + H2O





First step is protonation of the carbonyl O of benzoic acid, so draw arrow from that O atom to an H+, and another arrow from the C=O bond to the carbonyl O atom. This will give you a structure that has two -OH groups on the C atom, and don't forget to place the positive charge there as well.


Second step is for the lone pair of electrons on the O atom of CH3OH to bond to the positively charged C atom. The intermediate structure has two OH groups and the OHCH3 group bonded to the C atom now, and the positive charge has moved to the methanol O. To show this you draw the curly arrow from the O lone pair to the C+, and a curly arrow from the methanol O-H bond to the methanol O atom.


Third step, the electrons from one of the C-OH bonds captures the H+ from the intermediate structure. Draw a curly arrow from that bond to the H+. This will leave a + charge on the C atom again. To get rid of that and complete the reaction sequence, the electrons from the O-H bond shift to refrm the C=O bond, so draw a curly arrow from the O-H bond to the +C-O bond and finish up with the final structure of methyl benzoate.





It would be so easy to show this with pictures...How do you draw the mechanism (with curly arrows) for the reaction of methanol and benzoic acid?
Yes, the ratios are one to one- though extra methanol won't hurt anything. But to draw out the mechanism? I have no software to do that with. Does Yahoo answer have such software??? Basically, protonated methanol attacks the carbonyl function in the acid to form an intermediate which then decomposes to form ester and water
Buy chem draw thats how. the arrows always point away from where the electrons are being transferred to. Without any structures, its very difficult to tell you how to do it. The acohol from methanol and one hydrogen from benzoic acid form the water, and when the methyl doesnt have the alcohol, it can bind to the benzoate fairly easily.





Look in any ochem book, this is pretty standard.