Microwave spectrum and molecular conformation of p-fluoroanisole

Abstract

The microwave spectrum of the normal isotopic species of p-fluoroanisole has been measured for the ground vibrational state and for the first excited torsional state about the Ar—O bond. The rigid rotor rotational constants were found to be: v= 0, A= 4883.87 MHz, B= 972.475 MHz, C= 815.540 MHz; v= 1, A= 4868.62 MHz, B= 972.675 MHz, C= 816.488 MHz. The values of Δ(I_a+I_b–I_c) for the two states (Δ°= 3.476 a.m.u. Ų, Δ¹= 4.413 a.m.u. Ų) were found to be consistent with a planar framework of heavy atoms.