While less widely studied than amides, similar effects are observed with twisted anilines such as benzoquinuclidine 3 7 and Tröger's base 4, in which conjugation between the nitrogen lone pair and aromatic group are disrupted. The orthogonality of the nitrogen lone-pair with the arene in 3 manifests itself, for example, in the anomalous basicity of the amine (pK a = 7.8, c.f. 5.2 for dimethylaminobenzene), the observation of meta-substitution in S E Ar reactions under acidic conditions, and in anomalous photophysical behaviour of donor-acceptor compounds containing this motif.