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The Microwave Spectrum and Structure of CH2O–H2O

✍ Scribed by F.J. Lovas; C.L. Lugez

Publisher
Elsevier Science
Year
1996
Tongue
English
Weight
121 KB
Volume
179
Category
Article
ISSN
0022-2852

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✦ Synopsis

The microwave spectrum of the formaldehyde -water complex ( CH 2 O -H 2 O ) has been studied with a pulsedbeam Fourier transform Fabry -Perot cavity spectrometer. Both a-type and b-type transitions were observed for each of the isotopic species studied. To provide additional structural information, the spectra of H 2 O, HDO, and D 2 O substituents combined with H 2 CO and D 2 CO were assigned. Measurement of the dipole moment components yielded the values m a Å 3.379 ( 13 ) 1 10 030 Crm (m a Å 1.043 ( 4 ) D ) and m b Å 2.54 ( 20 ) 1 10 030 Crm (m b Å 0.76 ( 6 ) D ) and indicated that the dipole moment vectors are anti-aligned. The molecular structure derived from the moments of inertia has a center of mass separation of 3.00 ( 3 ) A ˚with the C 2£ symmetry axes of the monomers oriented at 19.3Њ from parallel with the dipole moments opposed. The complex is quite strongly bound with a harmonic pseudodiatomic stretching force constant, k s Å 8.93 N /m, and hydrogen bond lengths of approximately 2.68 A ˚between the water oxygen atom and a CH 2 hydrogen atom, and 2.03 A ˚between a water hydrogen atom and the oxygen atom of H 2 CO. Expanded uncertainties ( coverage factor k Å 2, i.e., two standard deviations ) are shown in parentheses for each experimental value reported above.

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