Primary alkoxide

The same products may be made from primary alkoxides by the violent reaction with elementary chlorine or bromine. A radical mechanism has been proposed to account for the oxidation of some of the alkoxy groups (54) ... 

If we consider the case of a simple alkyl ketone in a protic solvent, for example, we see that hydroxide ion or primary alkoxide ions will convert only a fraction of a ketone to its anion. 

The calculations also suggested that 5 was favored over 6 by 2.4 kcal mol 1 as found experimentally. The explanation was based on the higher stability of a tertiary alkoxide compared to a primary alkoxide [15], which outweighed the opposite trend for radical stabilization. Epoxide opening was irreversible [16]. 

Phenyl azide reacts with primary alkoxides to give 1-phenyltriazole derivatives. Two moles of azide are required, the seeond being reduced to aniline. No meehanism has been proposed for the reaction ... 

By comparing the approximate pA values of the conjugate acids of the bases with those of the carbon acid of interest, it is possible to estimate the position of the acid-base equilibrium for a given reactant-base combination. If we consider the case of a simple alkyl ketone in a protic solvent, for example, it can be seen that hydroxide ion and primary alkoxide ions will convert only a small fraction of such a ketone to its anion. 

Alkoxides of nickel(II) are conveniently prepared according to equation (177) in anhydrous conditions.1487 1488 All of these compounds are insoluble in the common organic solvents. Complexes with primary alkoxides are green and six-coordinated complexes with secondary and tertiary alkoxides are tetrahedral with colours ranging from blue to violet. All of the complexes decompose at about 90-100°C. The complexes with secondary and tertiary alkoxides undergo alcoholysis reactions when dissolved in primary alcohols. An interesting insertion reaction occurs when nickel alkoxide reacts with some isocyanates (equation 178).1489... 

The great synthetic utility of the reaction of alkyllithium and Grignard reagents with ketonic functions has been well documented.105 These reactions take place via the intermediacy of alkoxy derivatives formed by addition of the M—C bond across the C=0 function. Hence ketones, aldehydes and formaldehyde will lead to tertiary, secondary and primary alkoxides, respectively. This type of reactivity is known for a number of other carbanionic metal alkyl derivatives, both main group and transition metals, although the synthetic utility of the reactivity has in most cases not been well documented. 

In the addition of hydride donors to aldehydes (other than formaldehyde) the tetrahedral intermediate is a primary alkoxide. In the addition to ketones it is a secondary alkoxide. When a primary alkoxide is formed, the steric hindrance is smaller. Also, when the C=0 double bond of an aldehyde is broken due to the formation of the CH(0 M ) group of an alkoxide, less stabilization of the C=0 double bond by the flanking alkyl group is lost than when the analogous transformation occurs in a ketone (cf. Table 9.1). For these two reasons aldehydes react faster with hydride donors than ketones. With a moderately reactive hydride donor such as NaBH4 at low temperature one can even chemoselectively reduce an aldehyde in the presence of a ketone (Figure 10.6, left). 

The primary alkoxides of these metals do not decompose at 300°C, as decomposition of these compounds requires much higher temperatures, whereas tertiary alkoxides decompose at much lower temperatures, yielding amorphous products. These results indicate that heterolytic cleavage of the C-0 bond yielding car-bocation and metaloxo anion (>M-0 Equation 2.3) is the key step, and stability of the carbocation determines the reactivity of the metal alkoxides ... 

As described in Section III.B.l, decomposition of primary alkoxides in inert organic solvents requires temperatures much higher than 300°C, but in alcohols they may decompose at relatively low temperatures. The carbocation formed by the heterolytic cleavage of the C-0 bond is only poorly solvated in the inert organic solvent therefore the reaction barely proceeds. On the other hand, in alcohols, carbocation is solvated, which lowers the activation energy for the decomposition of alkoxide. For example, aluminum ethoxide does not decompose in toluene at 300°C, while it does decompose in ethanol, yielding the alkyl derivative of boehmite. 

Since primary alkoxide of zirconium does not decompose in toluene, and therefore hydrolysis of the alkoxide in inert organic solvent followed by hydrothermal crystallization of the hydrolyzed product is examined. In this method, the alkoxide solution in an inert organic solvent is placed in a test tube, which is then placed in an autoclave. The desired amount of water is placed between the test tube and the autoclave wall. When the autoclave is heated, the water evaporates and is dissolved into the toluene solution from the gas phase, where hydrolysis of the alkoxide takes place, followed by hydrothermal crystallization of the hydrolyzed products. 

The resonances in the butyl ether region occur in three distinct bands. Chemical shift data for the a carbon atom resonances in about 20 ethers indicate that the resonances centered about 872.9 may result from hindered aryl ethers, for example, butyl 2,6-dimethylphenyl ether, butyl benzyl ethers, or butyl n-alkyl ethers, for example, dibutyl ether. The resonances in this region could arise from tetrahydrofuran residues in the coal product. However, the results obtained in this laboratory and in Larsen s laboratory are much more compatible with interpretations that exclude the involvement of tetrahydrofuran and focus on the reactions of the labeled butylation reagent with 2,6-disubstituted phenoxides, benzylic oxides, and primary alkoxides liberated in the formation of the coal polyanion. The most intense resonance centered at... 

Note that the primary alkoxides (e.g., ethoxides) of some later 3d metals such as Mn11, Fe11, Co11, and Ni11 do not undergo alcoholysis (7, 19) or transesterification with tert-butanol or butyl acetate, whereas their terr-butoxides M(0-t-Bu)2 are easily converted into ethoxides with ethanol. 

ROP is carried out in solution, in the melt, in the bulk or in suspension. The involved mechanism can be ionic (anionic or cationic), coordination-insertion or free-radical polymerization [19].The cationic pol)rmerization is initiated by only two catalysts, trifluoromethane-sulphonic acid and its methyl ester [10, 15]. Initiators such as potassium methoxide, potassium benzoate, zinc stearate, n-, sec-, fer-butyl lithium or 18-crown-6-ether complexes are added for the anionic polymerization to induce a nucleophilic reaction on the carbonyl to lead to an acyl-oxygen link cleavage. According to Jedkinski et al. only the primary alkoxides, such as the first mentioned catalyst, can yield polymers with negligible racemization, transesterification and termination [10]. 

Examples where the cyclization involves replacement of a fluoride are more numerous. The initial observation involved the trapping of (o-lithiofluoro-ben-zene)Cr(CO)3 with y-butyrolactone. A primary alkoxide (10) is released which spontaneously cyclizes to 11 by replacement of fluoride. 

This reaction was shown to be general. In the absence of an added aldehyde, primary alkoxides give dimeric esters, RCHzOCOR, and secondary alkoxides are converted into ketones. If an aldehyde (RCHO) is added to either reaction, esters are formed, R CH20C0R from a primary alkoxide and R R CHOCOR from a secondary alkoxide. 

The primary alkoxide can attack intramolecularly the lactone carbonyl, leading to a new lactone, that besides suffers an attack by methoxide on the epoxide. Ahematively, the primary alkoxide can open intramolecularly the epoxide producing an oxetane. 

Hyperbranched polyethers can be synthesized via the A2+B3 approach, when diepoxides (3-24) are reacted with triols, such as TMP. Emrick et al. used 1,2,7,8-diepoxyoctane as the A2 monomer and TMP as the B3 monomer with tetra-n-butylam-monium chloride as the nucleophilic catalyst. Nucleophilic attack of the chloride ion on an epoxide at the less-hindered terminal carbon led to the formation of secondary alkoxide. Due to the equilibrium between primary and secondary alk-oxides via proton exchange, nucleophilic attack of primary alkoxides on the epoxide rings resulted in the formation of aliphatic hyperbranched polyether. As the feed ratio of the diepoxide and TMP was varied from 1.5 to 3, the resulting hb polyether contained two types of terminal units (T), one type of dendritic unit (D), and linear units (L) as shown in Scheme 4. The polydispersity index (PDI) of the polyether increased with the increase of molecular weight (from 1.5-1.8 at M = 1000 up to 5.0 at Mw = 7000). The products are viscous liquids with glass transition temperatures below room temperature. 

Bradley D C, Carter D G (1961) Metal oxide alkoxide polymers part 1. the hydrolysis of smne primary alkoxides of zirconium. Can J Chem 39 1434-1443... 

In contrast to earlier transition metals, some of the later 3d metal (Ni and Co) alkoxides exhibit an interesting variation in their alcoholysis reactions for example, secondary and tertiary alkoxides of these metals undergo facile alcoholysis with primary alcohols, whereas their primary alkoxides do not appear to undergo alcoholysis with tertiary, secondary, or even other primary alcohols. - ... 

The primary alkoxide derivatives of alkaline earth and other metals of group 2 are generally insoluble nonvolatile compounds whereas their highly branched alkoxides... 

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