NMR Subspectral Analysis Applied to Polyfluorobenzenes C6HnF6–n. II. 1,2,3,4-Tetrafluorobenzene

The nuclear magnetic resonance spectrum (¹H and ¹⁹F) of 1,2,3,4‐tetrafluorobenzene is described. Subspectral analysis is applied to this AA′MM′XX′ system, and the direct method of analysis is used for the part of the spectrum that cannot easily be expressed in closed form because of the two 4 × 4 Hamiltonian matrices. The magnitudes of the coupling constants fall within ranges of these known for similar molecules. The simultaneous appearance of $J_{\mathrm{FF}}$ 's ortho and a $J_{\mathrm{HH}}$ ortho makes it possible to establish firmly that these two types of $J$ 's have opposite sign.