Bond distances dimethyl ether

Use Learning By Modeling to make models of water, methanol, dimethyl ether, and di-te/t-butyl ether. Minimize their geometries, and examine what happens to the C—O—C bond angle. Compare the C—O bond distances in dimethyl ether and di-te/t-butyl ether. 

The main conseqnences of the solvation are fonnd to be the increment in bond lengths between the enolate oxygen atom and the lithinm in the mono and the disolvated a) enolates, together with the increment in the Li-Osolvent bond. However, the trend con-tinnes np to trisolvated species 3b (Fignre 4), where the Li-O distance is fonnd to be less than that in isolated species. These characteristics of larger Li-dimethyl ether distance (dne to the steric hindrance) and the absence of coordination to the double bonds snggest an ionic interaction of Li with enolate oxygen. 

Similar constancy is shown by other covalent bond distances (with certain exceptions that will be discussed later). For the carbon— oxygen single bond, for example, the value 1.43 A has been reported for methanol,4 ethanol, ethylene glycol, dimethyl ether, paraldehyde, metaldehyde, and many other molecules this value is accepted as standard for the C—O bond. 

Olah et al.603 have observed the formation of cation 309 (protonated fluorometha-nol) upon treatment of formaldehyde in HF-SbF5 [Eq. (3.81)]. When Minkwitz et al.605 attempted to isolate salts of the ion, however, the hydroxymethyl(methylidene) oxonium ion 310 was obtained [Eq. (3.81)]. Crystal structure analysis of the hexafluoroarsenate salt shows that cations and anions are connected by short H -F distances, forming a three-dimensional network. The bond lengths of the C-0=C fragment (1.226 and 1.470 A) are longer than those in formaldehyde (1.208 A) and dimethyl ether (1.410 A). The C—O—C bond angle is 121.2°. 

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