Structure methoxide

The generally accepted mechanism for nucleophilic aromatic substitution m nitro substituted aryl halides illustrated for the reaction of p fluoromtrobenzene with sodium methoxide is outlined m Figure 23 3 It is a two step addition-elimination mechanism, m which addition of the nucleophile to the aryl halide is followed by elimination of the halide leaving group Figure 23 4 shows the structure of the key intermediate The mech anism is consistent with the following experimental observations... 

Write the most stable resonance structure for the cyclohexa dienyl anion formed by reaction of methoxide ion with o fluoronitrobenzene J... 

Write equations describing the addition-elimination mechanism for the reaction of hexafluorobenzene with sodium methoxide clearly showing the structure of the rate determining intermediate j... 

Pentafluoro 6 nitrobenzene reacts readily with sodium methoxide m methanol at room temperature to yield two major products each having the molecular formula C7H3F4NO3 Suggest reasonable structures for these two compounds... 

A careful study of the reaction of 2 4 6 trinitroanisole with sodium methoxide revealed that two different Meisenheimer complexes were present Suggest reasonable structures for these two complexes... 

FIGURE 23.4 Structure of the rate-determining intermediate in the reaction of p-fluoronitrobenzene with methoxide ion. 

Diffuse functions have very little effect on the optimized structure of methanol but do significantly affect the bond angles in negatively charged methoxide anion. We can conclude that they are required to produce an accurate structure for the anion by comparing the two calculated geometries to that predicted by Hartree-Fock theory at a very large basis set (which should eliminate basis set effects). 

Draw Lewis stmctures for the anion resulting from addition of methoxide to fluorobenzene. Is the negative charge highly localized or is it delocalized over several positions Examine calculated charges for the anion. Are they in accord with those anticipated from the Lewis structures ... 

Treatment of l,2-difluoro-3,5-dinitrobenzene with methoxide leads to a single isomer of fluorodinitroanisole. Obtain the energies of the possible Meisenheimer complexes and predict the structure of the product. Is this outcome consistent with the previously-established directing effect of the nitro group ... 

Pyridine and dimethyl acetylenedicarboxylate in methanol yield - a mixture of (33) and (34). It is tempting to assume that a zwitterion (30) is first formed and that this then adds a proton followed by a methoxide ion (Michael addition) under the influence of both the positive charge on the ring and the assisting ester group. The resulting structure (31) could then add another molecule of the ester and cyclize, as indicated, to (32). Subsequent aromatization accompanied by loss of one, or the other, substituent at position 3 would lead to the two products, (33) and (34), actually isolated. 

According to the depth profile of lithium passivated in LiAsF6 / dimethoxyethane (DME), the SEI has a bilayer structure containing lithium methoxide, LiOH, Li20, and LiF [21]. The oxide-hydroxide layer is close to the lithium surface and there are solvent-reduction species in the outer part of the film. The thickness of the surface film formed on lithium freshly immersed in LiAsF /DME solutions is of the order of 100 A. 

Trialkyltin methoxides react with anhydrous hydrogen peroxide in ether to give the rather unstable bis(trialkyltin) peroxides, RsSnOOSnRs (214). Under the same conditions, dialkyltin dimethox-ides give polymeric peroxides, (RzSnOO), but, if an aldehyde is present, monomeric peroxides of the following structure are obtained (215). 

There is a great deal of evidence for the mechanism we shall discuss only some of it. Probably the most convincing evidence was the isolation, as long ago as 1902, of the intermediate 2 in the reaction between 2,4,6-trinitrophenetole and methoxide ion. Intermediates of this type are stable salts, called Meisenheimer or Meisenheimer-Jackson salts, and many more have been isolated since 1902. The structures of several of these intermediates have been proved by NMR and by... 

Dihydroepistephamiersine 6-acetate (7) was isolated from Stephania abyssinica as a homogeneous oil. The UV spectrum showed an absorption maximum at 286 nm, and the IR spectrum exhibited a band corresponding to an aliphatic ester carbonyl group at 1725 cm-1 (20). The H-NMR data are summarized in Table II. In chemical investigations, hydrolysis of 7 with barium methoxide gave an alcohol identical with 6-dihydroepistephamiersine (17), which on further treatment with mineral acid gave the known alkaloid, stephasunoline (17). Thus structure 7 was proposed for 6-dihydroepistephamiersine 6-acetate (20). 

Kimura and co-workers have synthesized a series of alkoxide complexes with the alcohol functionality as a pendent arm.447 674 737 A zinc complex of l-(4-bromophenacyl)-l, 4,7,10-tetraaza-cyclododecane was also synthesized by the same workers to mimic the active site of class II aldolases. The X-ray structure shows a six-coordinate zinc center with five donors from the ligand and a water molecule bound. The ketone is bound with a Zn—O distance of 2.159(3) A (Figure 12). Potentiometric titration indicated formation of a mixture of the hydroxide and the enolate. Enolate formation was also independently carried out by reaction with sodium methoxide, allowing full characterization.738... 

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