15min:

RANGA SUBRAMANIAN, Department of Chemistry, Wesleyan University, Middletown, CT 06459; ROBERT K. BOHN, Department of Chemistry, University of Connecticut, Storrs, CT 06269 \linebreak; AND STEWART E. NOVICK, Department of Chemistry, Wesleyan University, Middletown, CT 06459.

The microwave spectrum of 2-butynol, CH₃-CC-CH₂OH, has been investigated in the frequency range of 6 to 26.5 GHz. The spectra of the A and E torsional states were observed using Fourier transform microwave spectroscopy. Due to the presence of the cylindrically symmetric -CC- "spacer" between the methyl group and the rest of the molecule, the barrier to internal rotation, V₃, is only 7 cm^-1 . One conformer of 2-butynol was observed and assigned. The spectrum was analyzed with the -axis method using a very flexible Hamiltonian which gives a fit an order of magnitude better than that obtained with more standard code for internal rotation. The spectroscopic constants for 2-butynol are 23744.(18), 2093.429(1), 1966.358(1), and -400.34(2) MHz for A, B, C, and D_ab ; 0.48(1) kHz, -30.3(4) kHz, and 4.5(5) MHz for _J, _JK, and _K; and 0.1406(6), 6.93(9) cm^-1 , -33.4(7) kHz, and 192.0(9) GHz for , V₃, L_V, and F, respectively. The root mean squared error of the fit is 14 kHz. The angles between the internal rotor axis and the principal axes are _a = 12^\circ, _b = 78^\circ, with _c held fixed at 90^\circ. A preliminary fit for the torsional states of 2-pentyne, CH₃-CC-CH₂CH₃, will also be presented.