Infra-red spectrum of the tight (110) fold in n-C198H398

The alkane n-C198H398 has been crystallised in both extended chain and once-folded forms and annealed to produce materials with low concentrations of gauche bonds. The concentrations of the specific conformers detected by FTIR spectroscopy at −173 °C are calculated, using measurements on liquid n-hexadecane for calibration: values are all generally less than 2.0 per 100 carbon atoms, with extended chain samples showing values less than 1.0 per 100 carbon atoms. A subtraction spectrum (Once-folded chain sample minus Extended chain sample) shows positive bands at 1298, 1340, 1347 and 1369 cm−1, which are predicted in earlier calculations for a (110) fold, while additional positive bands at 1353 and 1363 cm−1 are assigned, respectively, to gg conformers and (tentatively) to strained gtg or gtg′ conformations.