Nematic phases in dilute transitions of rodlike molecules with carboxylic acid functional groups are studied using an Onsager-like theory with the additional term in the free energy describing hydrogen bonding. It is shown that the hydrogen bonds with a proper geometry enhance nematic ordering. The behavior of the system turns out to be completely different in the cases when molecules can form only dimers and when then can form hydrogen-bonded "polymers." In the latter case the molecules tend to form a completely ordered phase at low temperatures. The numbers of hydrogen bonds in the ordered phase and isotropic liquid are different. Therefore IR spectroscopy can be used for study of these systems.