CONCERNING BACK-BONDING AND POLAR EFFECTS IN AMINOALKYLBENZENE DERIVATIVES

The infrared and ultraviolet spectral properties of (CH3)2N(CH2)nC6H4COOCH3 (n = 1-4) were studied to determine the presence of intramolecular interactions between the nonbonded nitrogen electrons and the π system of the aromatic rings (i.e., back-bonding). The results show that such interactions do not contribute to either the ground or excited states. Kinetic data on the basic hydrolysis of the four esters likewise demonstrate the absence of nonconjugative orbital overlap. In the second portion of the paper we determine how the rate of alkaline hydrolysis of (CH3)3N+(CH2)nC6H4COOCH3 varies with the value of n. The compounds possess a quaternary nitrogen, a powerful electron-withdrawing group, and an ester functionality whose hydrolysis rate is sensitive to polar effects. The data are compared with Kirkwood-Westheimer calculations using spherical and ellipsoidal cavities. Hammett σp constants are reported for the (CH3)2N(CH2)n and (CH3)3N+(CH2)n groups where n = 1-4. © 1969, American Chemical Society. All rights reserved.