TABLE OF CONTENTS This section includes both alkyl aryl ethers 187 and diaryl ethers 188. In both cases, the oxygen atom causes an overall donation of electrons (+M, -I effect) into the aromatic nucleus, which, as in the case of phenols (Section 5), facilitates sulfonation of the aromatic ring although with aromatic ethers O-sulfonation (sulfation) is not possible. In the alkyl aryl ethers 187 the electron donation is enhanced by the inductive (+I) electronic effect of the alkyl group.
Huntress and Carten201a studied the action of chlorosulfonic acid on 42 aromatic ethers in order to determine the utility of the reagent for the characterization of aromatic ethers. 36 of the ethers were converted into their monosulfonyl chlorides and these were subsequently reacted with ammonium hydroxide to give the corresponding sulfonamides which were well-defined crystalline solids with sharp melting points suitable for identification of the original aryl ether. Six of the ethers examined failed to yield satisfactory monosulfonyl chlorides; namely: o-and p-methoxybiphenyl, diphenyl ether and the 4,4'-dibromo derivative as well as methyl and ethyl benzyl ethers.
In alkyl phenyl ethers, the preferred orientation of sulfonation is para with respect to the electron donating alkoxy group, but if this position is blocked by a substituent then sulfonation may occur ortho to the alkoxy group,1 ,3 ,5
Anisole (methyl phenyl ether or methoxybenzene ( 187; Ar = Ph, R = Me)) reacts with chlorosulfonic acid (two equivalents) in chloroform at 0 C...
