A Novel Connexion between Electrostatic Interaction and Intramolecular Configuration

Abstract

MORE than a year ago, we reported that the catechol derivatives (I) were being investigated in these laboratories with the object of increasing our knowledge of the relationship between chemical reactivity and intramolecular configuration¹. At that time we knew that 3 : 7-dioxa-1 : 2-benzcycloheptene (I, n = 3) brominates less readily in glacial acetic acid than do 1 : 3-dioxaindan and 1 : 4-dioxatetralin (I, n = 1 and 2 respectively)². This difference in reactivity has also been observed in their rates of hydrogen exchange³ and is a consequence of the puckered configuration of the seven-membered ring when n = 3; the O—CH₂ bonds are oriented out of the plane of the benzene ring and electromeric interaction between this ring and the oxygen atoms is partially inhibited. We expected this interaction to be a maximum in the essentially planar molecules of (I) (n = 1 and 2 respectively)⁴ and were surprised to find that both these substances are less reactive in the bromination and hydrogen-exchange reactions than is veratrole (II)^2,3.