3,3 -Dicarboxy-4,4 -dihydroxy

Kinetic studies on the bulk polyesterification of a,o-dicarboxy poly(hexamethylene adipate) with a,polymeric medium. Solomon s mechanism1 can be considered as reasonable. 

Only a few building blocks are available for the synthesis of ester-containing rigid mesogenic units, namely dihydroxy-, dicarboxy-, or (hydroxy, carboxy)-l,4-phenylenes, 4,4,-biphenylenes, and 2,6-, 1,4-, or 1,5-naphthylenes (Table 2.15). 

If the polyester synthesis is performed with equimolar amounts of diol and diacid, then, in addition to hydroxy, carboxy-terminated oligomers, dihydroxy- and dicarboxy-terminated oligomers are formed, as shown below. In a thermodynamic equilibrium, the molar ratios of the three functionality fractions should be 2 1 1, respectively. 

Tartaric acid (2,3-dihydroxybutanedioic acid. 2.3-dihydroxysuccinic acid). CjHnOs. is a dihydroxy dicarboxy lic acid with tun chiral centers. It exists as thedexlro- and lev oroialory acid the meso form t which is inactive owing to internal compensation , and the racemic mixture (which is commonly known as racemic acidl. The commercial product in the United Stales is the natural, dextrorotatory form. (R-R. /f l-lartaric acid lL(+)-tartaric acid), This enantiomer occurs in grapes as its acid potassium salt (cream of tartar). In the fermentation nf w ine, this salt forms deposits in the vats. 

Bredereck and Schmotzer (1044), from diaminomaleonitrile (DAMN hydrogen cyanide tetramer) and oxalyl chloride, prepared 2,3-dicyano-5,6-dihydroxy-pyrazine but Stetten and Fox (1049) could not prepare 23-diamino-5-hydroxy-pyrazine from glycine amide and oxamide. Section 11.3 lists preparations from a, -diamino or a, -diimino compounds and reagents other than a,0-dicarbonyl compounds (384) with additional data (1050) and oxidation of 23-dichloro-quinoxaline with hot aqueous potassium permanganate gave 23-dicarboxy-5,6-dihydroxypyrazine (1051). 

The condensation of diethyl succinate in the presence of ethanolic sodium ethylate and DBU in xylene at 80-100°C gave diethyl 2,5-dihydroxy-1,4-cyclohexadiene-1,4-dicarboxy late (77 J AP(K)5739). 

Furthermore, the group of Deimede [338-340] performed the synthesis of a-dicarboxy end-functionalized PS macromonomers by using ATRP (Scheme 72). Further polycondensation with dihydroxy end functionalized polyethylene oxide) led to alternating branched PS/poly(ethylene oxide) poly(macromonomers) (Scheme 72). These novel amphiphilic compounds afforded the formation of stable micelles, especially in THF or dioxane. 

The Nicolaus group has also isolated 5,6-dihydroxyindole, 2-carboxy-5,6-dihydroxyindole, and 5,6-dihydroxy-4,7-dicarboxy-indole in their degrada-tive studies of melanins. 

Dihydroxy-5,6,7,8-tetrahydro-l,4-phthalazinedicarboxylic acid (77) (or an 0X0 tautomer) underwent oxidation to l,4-dicarboxy-5,8-phthalazinequinone (78) (MnOj, CH2CI2, 20°C, 6 days 61%). ... 

Cl0H120g, Dimethyl 2,5-dihydroxy-1,4-dydlohexadiene-1,4-dicarboxy-late (form 2), 28, 427... 

As mentioned in the macromonomer section, a,co-dihydroxy polyacrylates and polymethacrylates were obtained by coupling two living chains that were initiated by an initiator containing a protected hydroxy group. Scheme 38 shows how coupling was obtained with l,4-bis(bromomethyl) benzene. " Similarly, a,o)-dicarboxy(PMMA) was prepared by initiating the polymerization with l,T-bis(trimethylsiloxy)-2-methylpropene-l (55). " ... 

Laporte P, Fradet A and MarSchal E (1987) Kinetics study on models of the noncat-al5 ed reaction between a,u -dicarboxy-polyamide-ll and a,co-dihydroxy-polyoxyalkyl-enes, J Macromol Sci-Chem A24 1269-1287. 

Deleens C, Foy P and Marechal E (1977) Synthesis and characterization of copolycondensate sequences poly (amide-seg-ether) - III. Study of the polycondensation reaction of a ,a -dicarboxy polyamide-11 and a ,a -dihydroxy polyoxyethylene. Determination of the rate constants and the activation energy, Eur Polym J 13 353-360 (in French). 

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