The Microwave Spectrum, Dipole Moment, and Conformation of

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The Microwave Spectrum, Dipole Moment, and Conformation of Bicycle[3.1 .O] hexane Robert L. Cook and Thomas B. Malloy, Jr.* Contribution from the Departments of Physics and Chemistry, Mississippi State University, Mississippi State, Mississippi 39762. Received October 18, 1973 Abstract: The microwave spectrum of bicyclo[3.1 .O]hexane has been studied in the range 26.5-40.0 GHz (R band) with a Hewlett-Packard Model 8400 Stark-modulated microwave spectrometer. The rotational constants (MHz) for the ground vibrational state have been determined to be A = 5542.955 k 0.014, B = 4236.818 + 0.007, and C = 3127.040 i. 0.007 from a least-squares fit to 22 lines including both a- and c-type low-J R-branch transitions. Model calculations indicate that the data are consistent with the boat conformation of the molecule. From the analysis of the Stark effect, the dipole moment components have been determined to be lpol = 0.093 + 0.001 D and ipcl = 0.168 0.002 D yielding a total dipole moment p = 0.192 + 0.003 D.

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here has been considerable research activity in recent years concerning the determination of the conformations and low-frequency vibrational modes of ring molecules by far-infrared, Raman, and microwave spectroscopy.’12 Part of this activity has conterned the low-frequency vibrations and conformations of some analogs of bicycl0[3.1.0]hexane.3-~ These have included 6-oxabicyclo[3.1.0]hexane,3~4 3-oxabicyclo[3.1.0]he~ane,~1’3,6-dioxabicyclo[3.1 . O ] h e ~ a n e , ~and