Microwave investigations

Geometrical Parameters of Thiophene from Bar s et al. Microwave Investigation"... 

In a microwave investigation, Lopata and Kuczkowski (Lopata, A. D. Kuczkow-ski, R. L., J. Am. Chem. Soc., 1981, 103, 3304-3309) determined that the equilibrium geometry of FCH2— —CHO was as shown below. Explain the near 90° orientation of the CF bond relative to the plane of the rest of the molecule (the explanation is the same as for the anomeric effect in sugars.)... 

These expected valueB of bond lengths are in reasonably good agreement with those reported from the microwave investigation 2.70 0.01 A for thallium-carbon and 1.43 0.02 A for carbon-carbon. 

One interesting species, unknown until recently, is HOF, which was studied by Peslak et al.,611 and electron-density contour maps were described. More recently, it was studied by Kim and Sabin.512 The computed bond lengths with a near-minimal GTO basis were i (H—O) = 1.080 A, J (0—F) = 1.450 A, and 0 = 100.8°, in fair agreement with the results of a microwave investigation. Force constants were computed and the population analysis was reported. A more extensive basis set was used in a similar calculation by Ha, who computed a dipole moment of 2.72 D.513... 

As can be seen, in each case the outermost pair of electrons occupies an s orbital, so that the molecules are normally divalent. A number of alkaline earth diatomic molecules have been studied by optical spectroscopy and double resonance methods. We have already described the very early microwave investigations of BaO in both its ground X 1 + and excited A 1 X states, and now proceed to discuss other molecules in this series. We describe these in their chronological order. 

McLay 3) has reported the molecular structure from his microwave investigations. The principal moments of inertia are rt-39, -39 2... 

In the second method, the ground-state rotational constants obtained from the analysis of an optical spectrum are compared with the constants obtained from a microwave investigation. Some values for cw-glyoxal are given in Table 4. Again it is found that it is necessary to multiply the statistical standard deviations of the constants by factors from 3 to 6 to obtain realistic estimates of the accuracy. The correlation matrix obtained from the analysis of the optical spectrum is given in Table 5. 

The microwave investigations were performed in. the same temperature range. The temperature dependence of both d.c. and microwave conductivities of TMBTP.HCNB complex exhibit an exponential character over the whole temperature range with... 

However, the half-chair conformation is not the only one in which planarity can be achieved. The classical boat conformation also fulfils the stereoelectronic requirements for maximum lone pair-carbonyl overlap, and is quite close to the half-chair in energy microwave investigations, and concordant force-field calculations indicate that in the gas phase the classical boat conformer of 8 valerolactone (XII) lies only ca. 0.6 kcal above the half-chair [35]. In CDCI3 and solution, 2,3,4-tri-O-... 

The question whether the structure of diazomethane and ethyl diazoacetate was linear or cyclic was clarified in favor of the linear structure by Boersch s X-ray diffraction investigation in 1935 (see Sect. 1.1). We start this section with the discussion of bond lengths and bond angles of diazomethane on the basis of Boersch s results and those of the microwave investigation of Cox et al. (1958) and Moore and Pimentel (1964 b) (Fig. 5-1). 

Both IR and NMR data indicate that in methanol solutions solvation of both cations and anions occurs by primary solvent molecules which are strongly hydrogen-bonded to those in the bulk solvent This result has been confirmed and extended to other protic solvents through microwave investigations on alkali metal halides and salts of divalent cations in methanol, ethanol and formamide Alkali salt ion pairs in protic solvents show cation-anion distances, as found by calori-... 

Extensive laser-microwave investigations have also been performed in the spectrum of NH2. Hills and Curl, Jr. observed strong electric dipole microwave transitions between a previously unobserved rovibronic level and the J = 1/2 and J = 3/2 spin-rotational levels of ho, A ir(0,10,0), respectively. The NH2 molecules passed through a resonant half-wave microwave cavity with a 60-mW single-mode cw dye laser beam along the axis. The microwave field was amplitude modulated, and the laser-excited fiuorescence signal was detected with a phase sensitive amplifier. Microwave transitions in that part of the NH2 spectrum were used by Hills to assign numerous optical transitions. 

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