The Case of Malonate

From a synthetic point of view, the variety of coordination modes represents a challenge. The flexibility of the ligand does not allow the formation of a determined pattern in the coordination that can be repeated synthesis after synthesis. Moreover, the subtle variation of different features of the synthetic procedure could afford different crystal structures. 

Is it possible to get a further condensation of these chains The appendance of other [Cu(H20)3] groups to the main [Cu(mal)2(H20)2] entity to yield a 2D coordination polymer seems to be the next step. However, unexpectedly, the 

The addition of monoethanolamine (mea) to the aqueous copper(II)-malonate solution increases the pH of the reaction medium further than that of the third complex and favors the formation of [Cu(mal)2] to give the complex [Cu(H20)3][Cu(mal)2]2 2H20 (Fig. 19e). The structure consists of the same regularly alternated chains observed in [Cu(H20)3][Cu(mal)2(H20)] , which intersect in such a way that carboxylate groups of the [Cu(mal)2] unit in one chain occupy the apical position of the copper atom of the same unit of the adjacent chain. 

The structural complexity in these compounds (nuclearity ranging from discrete entities to ID or 3D compounds is associated with different carboxylato-bridging modes of mal and different structural functions of water molecules. Most of these complexes have been magnetically characterized, and they exhibit ferromagnetic coupling through the carboxylate-malonate bridge.  

FIGURE 21. Perspective view along the a-axis of a fragment of the hydrogen malonate-bridged layer in [Cu(Hmal)2]. 

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In the case of malonic acid, CH2(COOH)2 propane, CH2Me2 or any other molecule of the form CH2Y2, if we replace either of the CH2 hydrogens by a group Z, the identical compound results. The two hydrogens are thus equivalent. Equivalent atoms and groups need not, of course, be located on the same carbon atom. For example, all the chlorine atoms of hexachlorobenzene are equivalent as are the two bromine atoms of 1,3-dibromopropane. 

Although the reaction mechanism of this type of reactions is not fully elucidated, it is easily anticipated that no intramolecular special stabilization effect for the carbanion generated from decarboxylation is expected, different from the case of malonic acid-type compounds. Moreover, cinnamic acid derivatives that have both the electron-donating and withdrawing substituents have been reported to undergo this reaction. This fact suggests that the enzyme itself stabilizes the transition state without the aid of mesomeric and inductive effects of the other part of the substrate molecule itself. If such unknown mechanism also works for other... 

With diketene, intermediates of type (III) were isolated and subsequently cyclized under basic conditions following step (b). In the case of 3-oxo-carboxylic acid esters or 3-acyl Meldrum s acids, cyclization step (b) immediately follows reaction step (a), if a slight excess of amine is employed (85TH1 87TH1). Note that conversion of (III) to (V) involves the (IH)-enol (Table I cf. 75BSF2731). The relatively low yield in the case of malonic acid ester, as well as the failure of the reaction with the non-enolizable diphenyl phosphinylacetic ester and cyanoacetate, points to the participation of an enol structure of (III). 

Oxalate viologen ion pair complexes have been examined in detail under pulsed laser flash and continuous photolysis [205], As the photolysis leads to the oxidation of oxalate dianion, the strongly reducing CO 2"is formed after decarboxylation and a second MV2 + is reduced, generating another equivalent of MV +. Malonate, succinate, glutarate, polyacrylate and polymethacrylate were also tested and found to be effective as CTC donors for MV + formation. In the case of malonate, decomposition of the carboxylate was not accompanied by MV2 + consumption. This was attributed to the efficiency of a back electron transfer step following immediately the decarboxylation [206]. 

Nucleophilic cleavage is especially useful for initiating the decarboxylation of P-keto esters and malonates without the retro-Claisen competition that frequently attends traditional base-catalysed hydrolysis [Scheme 6.7].27>2S In the case of malonates, only one of the ester functions is cleaved.29 A P-carbonyl group is... 

In the case of malonic acid and other compounds when the methylene group is linked to two carboxyl groups the sodium compounds are more easily formed than are the sodium compounds of the alkyl radicals themselves. These sodium compounds of malonic acid ester, are especially reactive toward alkyl halides with the result that the alkyl radical is introduced into the malonic acid ester in place of the sodium, i.e.y in place of hydrogen of the methylene group. This is shown by the following reactions. 

In the case of malonic ester, a cyclopropanone hemiaminal in the presence of titanium(IV) chloride was used as reagent giving product... 

In the last few years the combination of high spinning speed with 2D multiple quantum spectroscopy has opened up new possibilities in the area of hydrogen bond investigation by 1H solid state NMR. The field has been exhaustively reviewed by Schnell and Spiess [77]. In Fig. 3.2.26 is reported, for example, the information available by ID and 2D double quantum proton spectra in the case of malonic acid. Each signal can be unequivocally assigned to the respective proton, and the chemical shift of the carboxylic protons can be correlated to the 0-0 distance. Furthermore the intermolecular correlation between CH2 and COOH protons can be used as a constraint for establishing the conformation and array structure in the solid state. 

This would suggest that the second stage does not interfere with the ionisation of malonic acid in its first stage for the case of malonic acid on its own in water and at a stoichiometric concentration of 1 x 10 moldm. ... 

Different optimised reaction conditions and commercially available prolinols lej were found to be useful for the two processes, which satisfactorily yielded the products. The level of asymmetric induction observed was modest in the case of malonate esters. However, an unexpected... 

Experimental results on velocity of trigger waves in acidic bromate oxidation of ferroin have been reported by Field and Noyes [18] and Showalter [24]. A semi-quantitative comparison with experimental results shows that the observed velocity is proportional to square root of the product of [H+] and [BrOj ] as theoretically predicted. However, deviations have been observed depending on experimental conditions. Thus, in the case of malonic acid -I- bromate -t- manganous sulphate -1- ferroin in H2SO4 medium, the wave velocity is found [25] to be proportional to [Br03 ]y [H+]. Similar results are obtained for citric acid -I- BrOj -I- Mn - - H2SO4 system [26]. 

For example, if a solute added decreases the mutual solubility of the two liquids, the mutual solubility eventually becomes zero and the partition coefficient becomes equal to the ratio of the solubilities of the solute in pure solvents. If the mutual solubility is increased by the solute as in the case of malonic acid increasing the mutual solubility of ether and water, the concentrations of the solute in.the two layers tend to become equal and the partition coefficient then becomes one. The concentration... 

FIGURE 6.1 (a) One-dimensional interpolation of the potential V[qo(z)] as a function of the parameter z along the instanton path qo(z) for three ab initio methods in the case of malon-aldehyde. The points represent the ab initio data. The lines are obtained by piecewise cubic interpolation, (b) One-dimensional interpolation of the elements of Hessian 9 V [q(z)]/9 along the instanton path for MP2/cc-pVDZ ab initio method. Two examples are shown. (Taken from Reference [122] with permission.)... 

The aminolysis of esters may be carried out with aqueous ammonia [12], gaseous ammonia, and a variety of amines [13-15]. In the case of malonic esters, the methyl esters appear to react more readily, although ethyl esters have been used. Sodium methoxide is generally used as catalyst in either case [16]. 

The formation of complexes between the vanadyl cation and malonate, oxalate, L-tartrate, and racemic tartrate has been studied by the pressure-jump technique. Three relaxation times were found for the first two systems in the case of malonate they were attributed to the formation of the complexes [(VOOHlattial], [VO(mal)], and [VOfmaljg] -, whereas in the case of oxalate they were attributed to the formation of [VO(ox)] and the two isomeric complexes [VO(ox)2] j and [VO(ox)2]. The two relaxation times for the tartrate systems were ascribed to the formation of [VO(tar)] or [VO(tarH)]+ and [VO(tar)]2. It was also found that the formation of the dimer takes place stereospecifically such that no mixed complex (VO-L-tar-VO-D-tar) is formed. 

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