Knowledge Bank

Methyl tertiary butyl ether (MTBE), ethyl tertiary butyl ether (ETBE) and tertiary amyl methyl ether (TAME) are the oxygenated chemicals added to gasoline to reduce emissions. We have undertaken an investigation of these compounds to characterize their rotational spectra for trace-gas analysis. This work was carried out using one of NIST's FTMW Spectrometers, In MTBE, internal rotation splittings of the methyl top were observed $(V3=498(2)cm-1)$, whereas no splittings were observed in ETBE. For ETBE the fully extended conformer was observed and assigned. With TAME it appears that several conformers may be present and efforts are currently being made to assign these conformers. For MTBE and ETBE, sufficient sensitivity was obtained to perform the analysis for all $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}C$ and $\mathrm{<mrow\; data-mjx-texclass="ORD">18</mrow>}O$ species in natural abundance which allows a complete structural analysis for the heavy atom frames. The electric dipole moments were also determined for MTBE and ETBE. Rotational constants for MTBE and ETBE are (in MHz) A = 4382.840(1), B =2732.3925(4), C = 2730.7547(5) and A = 4088.391(1), B = 1561.7700(3), C = 1538.4138(4) respectively.