Methoxide ion

Furthermore, in cases of 2,4-dichloro- or 2.5-dichlorothiazole, halogen in position 4 or 5 can also be partially displaced using more than one equivalent of methoxide ion. 

If the reactions are carried out using a concentration of CHsO slightly less than that of halogenothiazole, the reaction almost quantitatively yields the 2-methoxy-5-nitrothiazole. The reaction of methoxide ion in excess with regard to 2-haiogeno-5-nitrothiazole, previously reported as leading to a mixture of unidentified products together with the expected 2-methoxy-5-nitrothiazole in low yields (97), can be explained on the basis of Scheme 14. 

When 5-halogeno-2-nitrothiazole reacts with methoxide ion. the leaving group is the nitro group in position 2, following Scheme 17 (86). 

The conjugate bases listed m Table 1 7 that are anions are commonly encountered as their sodium or potassium salts Thus sodium methoxide (NaOCH3) for example is a source of methoxide ion (CH30 ) which is the conjugate base of methanol... 

Alcohols are stronger acids than acetylene and so the position of equilibrium lies to the left Methoxide ion is not a strong enough base to remove a proton from acetylene... 

Benzene anion radical Methanol Cyclohexadienyl radical Methoxide ion... 

FIGURE 23 4 Struc ture of the rate determining intermediate in the reaction of p fluoronitrobenzene with methoxide ion... 

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

It would appear that this type of addition may not be confined to the addition of NH2 in liquid ammonia, since it has been observed that treatment of 2-chloro-3-dichloromethyl-pyrazine with an excess of methoxide results in the introduction of a methoxy group into the 6-position of the pyrazine ring (Scheme 9) (68TL5931). This reaction is best rationalized in terms of addition of the methoxide ion at the 6-position, followed by loss of chloride ion from the dichloromethyl side chain. 

The oxaziridine ring itself is stable towards alkali there is, for instance, no substitutive ring opening by hydroxyl ions as in oxiranes. 2-r-Butyl-3-phenyloxaziridine (56) is not attacked by methoxide ion in methanol during 12 h at room temperature 3-isopropyl-2-r-octyloxaziridine does not react at room temperature with either solid potassium hydroxide or potassium methoxide solution (57JA5739). 

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. 

C. Methoxide Ion, Arylsulfide Ions, and Other Charged Reagents. 312... 

A similar kinetic effect was reported for the reaction of 4-chloro-pyridine 1-oxide with methoxide ion at 50°, and still larger effects were obtained with the 2- and 3-isomers at the same temperature. ... 

The kinetic effects of some substituents on the fused benzene ring (CHg, NOg, OCHg, Cl) havc been determined recently for the reaction between the methoxide ion and the series of compounds aj-R-2-chlorobenzothiazole. Some of these effects are compared in Table XVIII with those observed at the 6-position of 2-chloroquino-lines and quinoxalines which are of the conjugative class. The data for... 

The order NO2 > Cl, which is known for the reactions of nitro-activated aromatic compounds, is also found for pyridine and quinoline derivatives. In the reaction of 2-chloro-4-nitroquinoline with methoxide ion, only the 4-methoxide derivative is formed, as shown by gas-chromatography, whereas 2,4-dichloroquinoline yields a mixture of the isomeric chloro-methoxy derivatives in comparable amounts. ... 

Bunnett and co-workers have shown that an or Ao-carboxy-late anion decreases the rate of reaction of 4-nitrochlorobenzene with methoxide ion but rather strongly increases the reaction rate with piperidine. This effect arises from an accelerative increase in the... 

In cases where comparable data are available, the activation energy for nucleophilic substitution by anions such as methoxide ion is... 

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