As for aldehydes , the hydrogen atoms on the carbon adjacent ("α to") the carboxyl group in esters are sufficiently acidic to undergo deprotonation, which in turn leads to a variety of useful reactions. Deprotonation requires relatively strong bases, such as alkoxides . Deprotonation gives a nucleophilic enolate , which can further react, ., the Claisen condensation and its intramolecular equivalent, the Dieckmann condensation . This conversion is exploited in the malonic ester synthesis , wherein the diester of malonic acid reacts with an electrophile (., alkyl halide ), and is subsequently decarboxylated. Another variation is the Fráter–Seebach alkylation .
The influence of renal impairment on the pharmacokinetics of haloperidol has not been evaluated. About one-third of a haloperidol dose is excreted in urine, mostly as metabolites. Less than 3% of administered haloperidol is eliminated unchanged in the urine. Haloperidol metabolites are not considered to make a significant contribution to its activity, although for the reduced metabolite of haloperidol, back-conversion to haloperidol cannot be fully ruled out. Even though impairment of renal function is not expected to affect haloperidol elimination to a clinically relevant extent, caution is advised in patients with renal impairment, and especially those with severe impairment, due to the long half-life of haloperidol and its reduced metabolite, and the possibility of accumulation (see section ).