Ddm group

We envisaged that the aforementioned sulfonated polymer-DDM may prove useful for the extractive esterification of those water-soluble acidic materials from aqueous solution that would not dissolve in methylene chloride for reaction with swollen polymer-DDM beads. Such compounds could include enzymes with some acidic character, but the risk is that desired enzyme activity may be lost by reaction with the DDM group. 

The 4,4 dimethoxydiphenylmethyl (Ddm) group, or to be more precise bis(4-methoxypheny])methyl, is another activated arylmethyl group that is labile towards oxidative and acidic cleavage. It has been used to protect p-lactams and in the example shown in Scheme 8.195, cleavage was effected with... 

By contrast with tertiary amines used in catalytic quantities, primary and secondary amines or acid anhydrides may be used to bring about the cure of epoxy resins by reaction in stoichiometric proportions. A typical amine curing agent used at this level is diaminodiphenylmethane (DDM), which reacts with an individual epoxy-group in the way shown in Reaction 4.17. 

Another aspect that has not been taken into account in the kinetic models discussed so far is the occurrence of ether-forming reaction through epoxide homopolymerisation or reaction with hydroxyl groups. In the system TGDDM with an initial DDM concentration less than the stoichiometric level the overall conversion of epoxide is greater than that expected for epoxide-amine addition 89, 97 98). 

Fig. 20 Stereoview of the common pharmacophore model for EpoA (green) and discodermolide (gray) derived from INPHARMA NMR and literature SAR data. Heteroatoms are displayed as spheres. O red, S yellow, and N blue. In this model, the C20-C24 tail of DDM is on the same side as the section C10-03 of EpoA, the carbamate group and the lactone ring occupy similar positions as the 7-OH group and C3-C4 unit of EpoA, respectively, while the C8-C15 segment of DDM corresponds to the C15-C18 region of the side chain of EpoA. (Reprinted with permission from [112]. Copyright 2006 Wiley-VCH Verlag GmbH Co. KGaA, Weinheim)...

In practical terms, the purification of aqueous solutions of XX on Rohm and Haas macroreticular resin XAD-16 proved to be very efficient (95-98% recovery of material with a purity of approximately 95%) and economical to carry out. This chromatographic purification step removes salts (especially phosphates) introduced at earlier processing steps in Antibioticos plant (Schemes 1 and 2), thereby enabling us to minimize the amount of DDM needed to fully esterify both carboxyl groups of XX 2.3 to 2.5 moles DDM per mole of XX generally proved sufficient.31 Although DDM is a relatively stable molecule (see footnote 20), its separate preparation does introduce some safety concerns. In practical terms, it should be possible to prepare... 

If in the 0 segment in Fig. 1 the alkyl group is replaced by an aryl group, e.g., EDA by DDM, or Sue A by methylhexahydrophthalic anhydride (MeHHPA), K2 becomes higher, the rigidity of the main chain increases, and Tg becomes higher (Table 1). 

If an alkyl chain (BDA) is substituted by m-phenylenediamine (MPDA), Tg is elevated by 45 °C (Table 3). However, almost the same effect is observed for DDM, while for MXDA having an alkyl-phenyl group, almost no effect on Tg is observed because the rigidity of the main chain is not increased enough. 

In both cases of cycloaliphatic and phenyl groups, nearly the same effects on the increase of Tg are observed. LARO and DDM can serve as example (cf. Table 3) 34). 

The critical excess for amino groups is more sensitive to the substitution effect within the amino group than the gel point conversion of a stoichiometric system and it is thus more suitable for characterization of q (Fig. 6). In this way, the value of q was found to be 0.33-0.40 for the aliphatic amino group and 0.18-0.24 for the aromatic group in DDM (Refs. 16 and 18 and impublished measurements). These values are close to these obtained in model reactions of compounds of low functionality. The determination of the critical molar ratio necessary for gelation i.e. the... 

Fig. 11. Weight fraction of the sol in DGEBA-PGE-DDM systems as a function of the molar ratio r. The fractions of epoxy groups of monoepoxide (PGE), s, and final conversion of epoxy groups determined by ir spectrometry are indicated. The curves were calculated for q = 0.19...

Figure 5. Chemical structure of dialkyl dihexadecyi malonate (DDM) (where fl and R2 are fatty alkyl groups).

A number of other diazocompounds have been studied. Warren (1961) has shown that the reaction of 9-diazofluorene in ethanol and in ethanol-water mixtmes is similar to that of diphenyldiazomethane. The rate of reaction is slower in deuteriated solvent and the operation of general acid catalysis was inferred from measurements with picric acid. As would be expected from the conjugation between the diazo and dibenzo-cyclopentadienyl groups in 13, the rate of reaction is slower than that of DDM (by a factor of about twelve) and there seems little doubt that both substrates react with a rate-determining proton transfer. Bate studies with substituted diazofluorenes yield a value of — p = l 6-l-9 depending on the substituent constants used (Warren, 1963 Warren and Yandle, 1965). This value is similar to that for the reaction of substituted diphenyldiazomethanes in toluene and is a further indication that the stability of diazoalkanes is quite sensitive to substituent effects. 

A further possibility is bimolecular displacement of nitrogen from the benzhydryldiazonium ion. Again, this may reasonably be ruled out on the basis of the stability of the carbonium ion. Since benzhydryl chloride is known to solvolyse exclusively by an S l mechanism in ethanol, the benzhydryldiazonium ion with its superior leaving group should, a fortiori, do so. This conclusion is confirmed by Bethell and Callister s finding that in aqueous acetonitrile the reaction of DDM with dissociated toluenesulphonic acid leads to the same product distribution as the solvolysis of benzhydryl toluenesulphonate (p. 354). 

Table 10.1 Geometric parameters of the NH3 group in trans-[Pd(NH3)2(N02)2] obtained from unconstrained DDM and Rietveld refinements for real and simulated powder XRD data.

Apart from these obviously biogenic compounds only very few definite anthropogenic substances were identified. Within the group of xenobiotics 2,4 - and 4,4 -dichlorophenylmethane, DDT-derived metabolites, were most abundant. A pyrolytic conversion of related DDT metabolites to DDM cannot be excluded. Thus the occurrence of DDM in the pyrogram is only suggestive for DDT group metabolites in general. 

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