Derivatization by composite reagents based on ω-bromoacyl chlorides [ClCO(C2)nBr (n = 1–4)] and pyridine was applied to study aliphatic and alicyclic alcohols and diols by ordinary and tandem electrospray ionization (ESI) mass spectrometry. The applied derivatization involves the simultaneous acylation of hydroxyl groups with an acyl chloride moiety and the quaternization of pyridine with a terminal bromoalkyl group. Under the ESI conditions, quaternary salts produce corresponding mono and diammonium cations, which are detected in the first-order mass spectra. Collision-induced dissociation (CID) of primary cations generated from monool derivatives gives rise to ammonium cations of the corresponding acids HOOC(CH2)n–N+(C5H5). The CID of primary dications affords the same cations which are also eliminated from dications to form mono-charged fragments. © 2017, Pleiades Publishing, Ltd.