FTIR and 1H-NMR studies of chiral (S)-(-)-2-methylbutyl 4′-(4″-hexyloxy-, (S)-(-)-2-methylbutyl 4′-(4″-(d13)-hexyloxy‒, (S)-(-)-2-methylbutyl 4′-(4″-octyloxy- and (S)-(-)-2-methylbutyl 4′-(4″-(d17)-octyloxyphenyl)benzoates