$-Nitro-N, N-dimethylaniline (I, R= H) is essentially a flat molecule due to the contribution of the quinoidal structure to the resonance. As the group R increases in size, there is an increasing repulsion between R and the amino3 and nitro4 groups. Remington3 has shown that the marked ultraviolet absorption (near 380 mp) of certain nitrobenzene derivatives is associated with the quinoidal limiting structure (I). The intensity of this band is steadily ...
[Gupta, Dharmendra N.; Hodge, Philip; Davies, J. Eric Journal of the Chemical Society, Perkin Transactions 1: Organic and Bio-Organic Chemistry (1972-1999), 1981 , p. 2970 - 2973]
