NaBH(OAc) may also be used for reductive alkylation of secondary amines with aldehyde-bisulfite adducts. Not all irreversible inhibitors form covalent adducts with their enzyme targets. In rat urine about 74,000 oxidative DNA adducts per cell per day are excreted. They are hard acids and react readily with ligands, forming adducts. NHCs and boranes form stable NHC borane adducts. The bisulfite adducts precipitate as solids from solution. With multiple acidic hydrogen atoms on the carbon acid higher adducts are also possible. VCl forms adducts with many donor ligands, for example, VCl(THF). It is a colorless liquid prepared by treating borane adducts with pinacol. Both BF and BFOMe are Lewis base adducts of boron trifluoride. Formaldehyde and its adducts are ubiquitous in living organisms. A simpler case is the formation of adducts of borane. LTA can form adducts with tissue DNA. The adducts are usually either octahedral or tetrahedral. Examples include salts of (tetraethylammonium)MgCl and adducts such as MgCl(TMEDA).