Line assignments and global analysis of the tunneling–rotational microwave absorption spectrum of dimethyl methylphosphonate

The geometry of organophosphonates: Fourier-transform microwave spectroscopy and ab initio study of diethyl methylphosphonate, diethyl ethylphosphonate, and diisopropyl methylphosphonate

“…Despite the ambiguity, experimental data and ab initio calculations, combined with recent studies of dimethyl methylphosphonate (DMMP) [14][15][16] and the Gseries nerve agents sarin, soman, and cyclosarin [11][12][13] can be used to make general comparisons in organophosphonate structures between R-group size and the number of low-energy conformers that may be available, the number of low-energy conformers observed, and the relationship of the RAO groups to the internal rotation of the PACH 3 group in DMMP, DEMP, and DIMP, and the motion of the PACH 2 CH 3 group in DEEP.…”

“…For instance, an interconversion tunneling mechanism related to the two, non-equivalent methoxy groups in DMMP was deduced from deviations in the ''A-state'' FTMW spectrum [14][15][16]. Similarly, the internal rotations of several organophosphonates PACH 3 methyl groups have been deduced from spectral features.…”

“…A thorough comprehension of the low-potential energy surface of the molecule (roughly defined as the region 6 $400 cm À1 above the ground state) is important in understanding such mechanisms. Towards this end, previous work has been reported for the spectra of chemical warfare agents sarin [11], soman [12], cyclosarin [13], in addition to the simulant dimethyl methylphosphonate (DMMP) [14][15][16], and several ''mustard gas'' simulants (for example, ethyl sulfide [2], divinyl sulfide, divinyl sulfoxide, or divinyl sulfone [17]). …”

Fourier transform microwave spectroscopy of 1,1-dimethylsilacyclobutane. Interplay of two types of large-amplitude motions: two-top internal rotation and ring puckering

“…Hougen [11,12] has put this approach on a firm basis by clearly defining the coordinate systems. Ohashi et al [13,14] applied his theory to several types of molecules; one recent example is DMMP (dimethyl methylphosphonate), a molecule that involves two types of large amplitude motions, as DMSCB does. In the present paper, we shall refer this approach to as H.-O.…”

“…We use the theoretical formulation which Ohashi and Hougen [13,14] developed to analyze the rotational spectra of DMMP, while properly paying attention to the difference between DMMP and DMSCB. The equilibrium configuration of DMMP is of C 1 symmetry, whereas DMSCB keeps C s symmetry even when the ring puckering is excited.…”