Rotational Spectra, Structure, and Electric Dipole Moments of Methyl and Ethyltert-Butyl Ether (MTBE and ETBE)

Abstract The rotational spectra of methyl and ethyl tertiary butyl ether (MTBE and ETBE) have been observed and analyzed using a pulsed-molecular-beam Fabry–Perot cavity microwave spectrometer. Both a - and b -type transitions are observed for each compound. Small CH 3 internal rotation splittings from the OCH 3 group of ∼1 MHz are observed for MTBE. The high sensitivity of the Fourier transform microwave (FTMW) technique allows observation and analysis of the rotational spectra of all 13 C isotopes and the 18 O isotopic species in natural abundance. For ETBE, the structural analysis indicates that the lowest energy form of the molecule is the completely extended conformer with C s symmetry. For both compounds, the bulkiness of the t -butyl group causes the COC angle to be 6° to 7° larger than that found in most other ethers.