Computer simulations on sprite initiation for realistic lightning models with higher‐frequency surges

[1] Computer simulations on transient luminous emissions in the mesosphere and lower ionosphere have been performed for realistic lightning modelings with fast-varying current surges (M components) superimposed on the lightning continuing current (CC). The algorithm used here is an electromagnetic (EM) code, which enables us to estimate self-consistently the reduced electric field, electron density, conductivity, and luminosity as a function of space and time by solving the Maxwell equations. It is found that M components in the CC with small amplitudes, but with a fast-varying EM effect, can initiate or enhance the occurrence of sprites. Even for a return stroke (RS) without CC, subsequent high-frequency current variations (like M components) are found to lead to dramatic changes in the sprite occurrence. The physics underlying these changes is studied by means of, e.g., temporal and spatial variations of luminosity, electron density, and conductivity. As the conclusion, the RS is a fundamental agency for spites, but high-frequency variations as EM effects exhibit an additional essential influence on sprite occurrence. These computational results are used to offer some useful ideas concerning the unsolved problems of sprites and halos, including polarity asymmetry, long-delay characteristics, and morphological shapes of sprites

Organic derivatives of antimony - 3. Alkoxy and chloroalkoxy derivatives of antimony

1. The action of an excess of chlorine on the corresponding alkoxy- and chloroalkoxy derivatives of Sb(III) produced trichlorodimethoxy-, dichlorotrimethoxy-, and trichlorodiethoxyantimony, which have not been described in the literature, as well as tetrachloromethoxy- and dichlorotriethoxyantimony. 2. The action of acetyl chloride on pentaethoxyantimony yielded chlorotetraethoxyantimony. 3. The ester interchange of pentaethoxyantimony with methanol yielded pentamethoxyantimony. 4. The reaction of SbCl3 with trimethoxy- and triethoxyantimony produced chlorodimethoxy-, dichloromethoxy-, and chlorodiethoxyantimony. © 1977 Plenum Publishing Corporation

Organic derivatives of antimony. IV. Association of alkoxy and chloroalkoxy derivatives of antimony (III) and (V)

1. Chlorotetramethoxyantimony was obtained by the action of acetyl chloride on pentamethoxyantimony. 2. Triethoxy-, tripropoxy-, and triisobutoxyantimony are partially associated under conditions of cryoscopy in cyclohexane, while triisopropoxy- and tri-tert-butoxyantimony are monomeric. Under ebullioscopy conditions in CCl4, 2-ethoxy-4-methyl-1, 3,2-dioxastibinane exists in a monomeric form. 3. According to the data of cryoscopic and ebullioscopic measurements, pentaethoxyantimony exists in benzene in a dimeric form. Dimers of tetrachloromethoxy-, trichlorodimethoxy-, and dichlorotrimethoxyantimony are partially dissociated in benzene. © 1979 Plenum Publishing Corporation

Stereochemistry of organophosphorus compounds 15. Synthesis and permutational lability of 1,6,10-trioxa-8,8-dimethyl[(5-methoxy)-5-phosphaspiro(4.5)]dec-2-ene

1. We have synthesized 1,6,10-trioxa-8,8-dimethyl[(5-methoxy)-5-phosphaspiro(4.5)]dec-2-ene, a compound in which the trigonal-bipyramidal phosphorus bond arrangment undergoes pseudorotation at temperatures below 36°C. Thermodynamic activation parameters for the pseudorotation process have been evaluated from the observed temperature variation of the parameters of the1H NMR spectrum. 2. The enol acetate of β-neopentylglycolphosphonepropionic aldehyde has been prepared. © 1978 Plenum Publishing Corporation

Vibrational spectra and structure of antimony (III) trialkoxides

1. According to their vibrational spectra, antimony trialkoxides of formula Sb(OR)3 with R=CH3, C2H5, n-C3H7, and i-C4H9 are associated; no signs of association are observed for the compounds with R=i-C3H7 and t-C4H9. 2. The molecules of antimony tri-t-butoxide in the liquid state at 20°C exist in the form of rotational isomers having C1 (Cs) and C3 (C3v) symmetry, with the C1 (Cs) conformer predominating. Upon freezing, the C3 (C3v) conformer remains in the crystal. © 1981 Plenum Publishing Corporation

Preparation and vibrational spectra of various esters and chlorides of antimonous acid

1. 2-Methoxy-, 2-methoxy-4-methyl-, 2-methoxy-5,5-dimethyl-, 2-chloro-, 2-chloro-4-methyl-, and 2-chloro-5,5-dimethyl-1,3,2-dioxastibinanes have been prepared. 2. The bands due to the group vibrations ν (Sb-O) and ν (Sb-Cl) have been identified in the infrared and Raman spectra of the acyclic and cyclic esters and chlorides of antimonous acid obtained. © 1976 Plenum Publishing Corporation

Detection of pseudorotation in dimers of pentaalkoxy derivatives of antimony on the basis of PMR spectrometric data

1. A mechanism has been proposed for intramolecular and intermolecular ligand exchange in a series of pentacoordinated derivatives of Sb. 2. An interpretation has been given for the temperature dependence of the NMR spectra within the framework of concepts as to the limiting stages of equilibrium reactions. 3. Activation energies have been determined for the process of rupture and formation of the dimeric bond, and an estimate has been made of the lower limit of free energy of activation of pseudorotation in the monomeric pentacoordinated form. © 1983 Plenum Publishing Corporation

Contribution of intermolecular associates and inversion of pyramid of antimony bonds in conformational exchange of certain 1,3,2-dioxastibinanes and 1,3,2-dioxastibepines

1. It has been shown for the first time by means of1H NMR that in solutions of cyclic compounds of trivalent antimony, dimeric structures with the participation, of endocyclic and exocyclic O atoms are realized. The molecular dynamics are determined by conformational conversions and also by the process of rupture and formation of dimeric bridge bonds Sb...O, this process of bond rupture and formation being the limiting stage of the overall process. The process mechanism has been established, and the energetics have been estimated. 2. The dominant conformations in the monomeric form have been determined, and the characteristics of the1H and13C NMR spectra are given for the particular compounds that have been studied. © 1985 Plenum Publishing Corporation

Production of some derivatives of 1,3,2-dioxastibinane and their vibrational spectra

1. 2-Chloro-, 2-methoxy-, and 2-tert-butoxy-4,6,6-trimethyl-1,3,2-dioxastibinanes and 2-tert-butoxy-5,5-dimethyl-and 2-tert-butoxy-4-methyl-1,3,2-dioxastibinanes were synthesized by the transetherification of chlorodiethoxy-, trimethoxy-, and tri-tert-butoxyantimony with the respective glycols. 2. According to the data on the vibration spectra, the 2-chloro and 2-alkoxy derivatives of 1,3,2-dioxastibinane are associated at the Sb-O bonds in the crystalline phase. The degree of association is determined by steric factors. 2-tert-Butoxy-4,6,6-trimethyl-1,3,2-dioxastibinane exists in the monomeric form. © 1985 Plenum Publishing Corporation

Reaction of trialkyl phosphites with α, β-unsaturated acids

1. The addition of trialkyl phosphites to α, β-unsaturated acids can proceed via the prior protonization of the trialkyl phosphites by the unsaturated acid. The dialkylphosphorous acids and unsaturated acid esters that are formed here react with each other to give the trialkyl esters of the corresponding β-phosphonocarboxylic acids. 2. Not excluded is the possibility that the above indicated reaction can also proceed simultaneously by the mechanism proposed by Kukhtin and Kamai, but without the formation of the cyclic phosphorane as the intermediate step. 3. Together with the trimethyl ester of β-phosphonopropionic acid, the cyclic anhydride of the methyl ester of β-phosphonopropionic acid is formed when trimethyl phosphite is reacted with acrylic acid. The cyclic anhydride is obtained in much larger amounts in the presence of acetic acid. The corresponding cyclic anhydride was isolated in the same manner when triethyl phosphite was reacted with methacrylic acid. © 1971 Consultants Bureau