Vibrational spectra and structure(s) of X(OR)₄ molecules with X  C,: Si and R = methyl, ethyl

Abstract

Vibrational spectra of tetramethoxymethane (TMM), tetraethoxymethane (TEM), tetramethoxysilane (TMS) and tetraethoxysilane (TES) have been recorded and assigned. DTA curves and temperature vs. time curves have been recorded in the region −150 to + 30°. No transition points have been observed, melting ranges are −1 to +2 (TMM); −16 to −12 (TEM); +10 to +16 (TMS) and −71 to −68° (TES). The liquid state of tetramethoxymethane (TMM) contains two rotamers; the skeleton C(OC)4 may have S4 or D2d symmetry. The S4 form is about 1 kcal/mole more stable than the D2d form of TMM in the liquid. Solid TMM consists probably of the D2d configuration only. There is no distinction between either configuration in tetramethoxysilane (TMS) as the rotation of methoxy groups around their SiO axes is apparently free for practical purposes. The methyl group of an ethoxy group in X(OC2H5)4 may occupy a gauche or a trans position relative to its XO bond. Rotational isomerism of this kind is probably present in tetraethoxymethane (TEM). Rotational isomerism is probably absent in tetraethoxysilane (TES).

A Raman Spectroscopic Study of the Initial Stages of Hydrolysis Oftetraethoxysilane

“…The origin of these peaks has been assigned to the Si0 4 asymmetric stretch and a CH 2 rock [9]. Neither of these peaks seems to be affected appreciably in solutions containing water:TEOS ratios of 2:1 or less, and in fact seem to increase somewhat in those containing one mole of water per mole of TEOS.…”

“…Figure 1 shows the evolution of Raman spectra for a solution of composition 1-4-1-0.05 in the minutes immediately following addition of the water fraction. The TEOS concentration in this solution is 2.1 M. The spectra shown can be interpreted on the basis of assignments made by Ypenburg for the spectra of TEOS [9]. The strong peak at 645 cm-1 is attributed to the symmetric SiO 4 stretch of the alkoxide.…”

“…Many studies have successfully applied Raman spectroscopy as a tool for the determination of structure of bulk glasses [2][3][4][5], gels and gels evolving toward glasses [6][7][8], and solution precursors and intermediates in the sol-gel process [9][10][11][12][13][14][15][16]. Critical information regarding the structure of glass surfaces and the nature of the amorphous network have been provided by this technique.…”

Novel reusable functionalized magnetic cobalt ferrite nanoparticles as oil adsorbents

“…Peaks at 1168 and 968 cm −1 belong to C–H rocking. The ethoxy group bound to the silicon atom (Si–OCH 2 CH 3 ) is characterized by peaks around 1100 cm −1 (Viart and Rehspringer, 1996;Ypenburg and Gerding, 1972). SiO 2 @CoFe 2 O 4 NPs show absorption peaks at 3388 cm −1 , which is characteristic for the O–H bond, whilst the peaks at 1100 and 1050 cm −1 correspond to Si–O–Si bonds (Heidari et al., 2009).…”

Thermal evolution of ladder-like silsesquioxanes during formation of black glasses

“…4-6). Literature data state that a band at 1900 cm -1 can be a combinational band or a residual bonding of -C:C-specimen [41,42]. Bands at 2050 and 2230 cm -1 can be attributed to the Si-H stretching vibrations (SiCSi-H and O 3 Si-H groups) [30,31,34].…”