Methoxide anion

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). 

Is para-nitrofluorobenzene more or less susceptible to attack by methoxide than fluorobenzene Calculate the energetics of the reaction. (Energies for phenyl fluoride and para-nitrofluorobenzene methoxide anion adducts are available.)... 

Electrostatic potential map for para-nitrofluorobenzene methoxide anion adduct shows most negatively-charged regions (in red) and less negatively-charged regions (in blue). 

Bidentate binding of two Lewis acidic boron centers to one methoxide anion was first reported in 1967 [241]. Further examples did not appear until 1985 [242]. Today, other bis(boronates) like 152 and 154-158 (Fig. 41) are known that can be applied to the selective complexation of amines and diamines [243-247]. 

The cycloadduct, l-phenyl-2,3-dihydro-l-benzothiophenium salt 59 is quite stable in the presence of hydroxide or methoxide anions at room temperature. When cycloadduct 59 reacted with sodium methoxide in methanol at 50 °C for 12 h, the ring opened product 243 was obtained in 96% yield (Scheme 41) <2003JOC731>. 

The attack of methoxide at the 5-position of the three 3-furanosidyl-l,2,4-oxadiazoles 102 led in each case to the 5-phenyl-l,2,4-oxadiazole 103 via the mechanism suggested in Scheme 10, whereby the oxadiazole 5-position is attacked twice by the methoxide anion, a process that is followed by ring closure and loss of acetate and methoxide <1999CAR157>. 

Two of three nitrofluorobenzene isomers react with methoxide, but the third is unreactive. Obtain energies of methoxide anion (at left), ortho, meta and para-nitrofluorobenzene, and the corresponding ortho, meta and para-methoxide anion adducts (so-called Meisenheimer complexes). Calculate the energy of methoxide addition to each of the three substrates. Which substrate is probably unreactive What is the apparent directing effect of a nitro group Does a nitro group have the same effect on nucleophilic aromatic substitution that it has on electrophilic aromatic substitution (see Chapter 13, Problem 4) Examine the structures and electrostatic potential maps of the Meisenheimer complexes. Use resonance arguments to rationalize what you observe. 

A study of gas-phase reactions of benzyl and methoxide anions with alkyl formate and other esters has revealed some differences in behaviour of these anions of comparable basicity.184 The delocalized benzyl anion and localized methoxide ion engage in exclusive transacylation and proton transfer, respectively, on reaction with alkyl formates. However, proton transfer is sufficiently exothermic to dominate when benzyl anion reacts with methyl acetate. Both anions react with methyl benzoate, methyl tiifluoroacetate, and methyl cyanofonnate by competing transacylation and. S n2 reactions. 

Pushing detection limits of nitroaromatic explosives into the parts per trillion (ppt) level requires sample preconcentration. Collins and coworkers used solid-phase extraction (SPE) of explosives from sea water which was followed by rapid on-chip separation and detection [18]. Explosives were eluted from SPE column by acetonitrile and were injected in the microchip separation channel. Lab-on-a-chip analysis was carried out in nonaqueous medium. The mixed acetonitrile/methanol separation buffer was used to produce the ionized red-colored products of TNT, TNB and tetryl [27,28]. The chemical reaction of the bases (hydroxide and methoxide anions) with trinitroaromatic explosives resulted in negatively charged products, which were readily separated by microchip... 

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