Abstract: | The 240 MHz NMR spectra of bipyrimidine in the nematic phase of p-methoxybenzylidene-p-n-butylaniline is analysed. The para H,H inter-ring distance is determined. The barrier to internal rotation of the inter-ring C? C bond is studied. Excellent agreement between experimental and calculated spectra is obtained using potential function V(?) = ½ ΣNVn (1 – cosn ?) with V1 = V2 = V3 = 0 cal mol?1 and V4 = 500 cal mol?1. |