Formanilide has been investigated by free-jet millimeter-wave absorption sp
ectroscopy. The rotational spectrum of the conformer with the formyl hydrog
en anti to the phenyl group has been assigned. Several rotational transitio
ns of the ground state have been measured for both normal and ND isotopic s
pecies. All the atoms of the peptidic group are coplanar to the ring. (C) 2
001 Academic Press.