Trimerization of unsymmetrical alkynes gives two isomeric benzenes. It is fuelled by very toxic unsymmetrical dimethyl hydrazine and nitrogen tetroxide. Regioselective intermolecular trimerization of unsymmetrical alkynes remains an unsolved problem. Also it is of two types, as pectus carinatum is symmetrical or unsymmetrical. Each stereoisomer is an unsymmetrical molecule, and thus has isocyanate groups with different reactivities. In unsymmetrical ethylated compounds, the methylene protons in the ethyl substituent are diastereotopic. All stages used UDMH (unsymmetrical Dimethylhydrazine) as fuel and dinitrogen tetroxide as oxidiser. Most triglycerides are unsymmetrical, being derived from mixtures of fatty acids. For unsymmetrical ketones, methods exist to control the regiochemistry of the deprotonation. The propellants used are unsymmetrical dimethylhydrazine (UDMH) and nitrogen tetroxide (NO). In this reaction, two unsymmetrical ketones are being condensed using sodium ethoxide. Mixed with unsymmetrical dimethylhydrazine it was used as Hydyne, a propellent for liquid-fuel rockets. Dimethylamine is susceptible to oxidation to unsymmetrical dimethylhydrazine, which air-oxidizes to NDMA. These faults rarely occur in practice as compared with unsymmetrical faults. Si(NCO) is also used as a precursor to such unsymmetrical ureas.