Premium
Vinyl ether hydrolysis. 30. Effect of β‐carboxy and β‐carbomethoxy substitution
Author(s) -
Kresge A. J.,
Ubysz D.
Publication year - 1994
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.610070608
Subject(s) - chemistry , hydrolysis , perchloric acid , carboxylate , reactivity (psychology) , ether , substrate (aquarium) , aqueous solution , vinyl ether , methacrylic acid , inductive effect , medicinal chemistry , acid hydrolysis , organic chemistry , monomer , medicine , oceanography , alternative medicine , pathology , geology , polymer
Rates of hydrolysis of the vinyl ether functional groups of ( Z )‐ and ( E )‐β‐methoxyacrylic acid and ( Z )‐and ( E )‐β‐methoxymethacrylic acid and their methyl esters were measured in aqueous perchloric acid solution. Additional rate measurements were also made for one substrate, ( Z )‐β‐methoxymethacrylic acid, in buffer solutions down to pH 7, and a rate profile was constructed. The results show that the β‐carboxy and β‐carbomethoxy substituents produce strong rate retardations, ranging from 2000‐ to 25 000‐fold, for both Z ‐ and E ‐isomers in both the acrylic and methacrylic acid series. The rate profile for ( Z )‐β‐methoxymethacrylic acid indicates that ionization of this substrate to the carboxylate ion form rises the rate of hydrolysis by a factor of 240. It is argued that this difference in reactivity of ionized and non‐ionized forms of the substrate is due to conjugative and inductive effects of the substituents, rather than β‐lactone formation as suggested in an earlier observation of the same phenomenon in a different system.