Butane-1,1,4-tricarboxylic acid

Vbcke, Z. physiol. Chem., 1930,191, 84. Butane-1 1 4-tricarboxylic Acid... 

In case C where jc = 1 the acid will be 1,2,4-butane tricarboxylic acid and when x = 2 the acid will be 1,3,5,6-hexane tetracarboxylic acid if the 1,2- groups are linked head-to-tail, and the 1,3,4,6- isomer if linked head-to-head. 

Yakubchik and his co-workers (1956, 1959 and 1962) have preferred to separate the acid derivatives by means of partition chromatography and compared the results with those obtained from an artificial mixture of those acids expected to be present. In the case of Ziegler-Natta catalyzed polybutadienes with less than 1% 1,2- units the presence of 1,4-1,2-1,4 sequences was indicated by the identification of some 1,2,4-butane tricarboxylic acid. Examination of their chromatograms suggests, at most, just a trace of any hexane tetra-carboxylic acid so that only a very small amount, if any, of 1,4-1,2-1,2-1,4 structures were present. Furthermore, no trace of any 1,2,3-propane tricarboxylic acid was found so there was no positive sign of any branching at the a-methylene position. On the other hand in the case of rubidium-catalyzed poly butadienes, which, like other polybutadienes prepared by the use of alkali metal catalyst systems, have a high 1,2- content, both hexane tetracarboxylic acid and 1,2,3-propane tricarboxylic acid were present in the ultimate products of ozonolysis. 

These results are consistent with a random distribution of the various units. The probability of a random sequence of r similar units (e.g. 1,2- units) is given by p (l-p) where p is the fraction of such units in the total. For the Ziegler-Natta polymers described by Yakubchik p = c. 0 05 so that the molar ratio of butane tricarboxylic acid to hexane tetracarboxylic acid should be about 20 1 whilst for the rubidium-catalyzed polymers which had a 1,2- content of about 50% the ratio should be about 2 1 (experimental results c. 1 7 1). 

Butane-1,2,4-tricarboxylic acid, A26.10, A"22 Dehydroquinic acid, A26.3 Butane-l,l,2-tricarboxylic acid, A28.14 Methyl hydrogen 2-acetoxysuccinate, A1.23... 

Figure 2.13 Hydrogen-bonded unit within the quaternary co-crystal cyclohexane-1,3,5-tricarboxylic acid l,2-bis(4-pyridyl)ethane l,4-bis(4-pyridyl)butane ortAo-xylene (2 2 1 ). The ortAo-xylene molecules are disordered in cavities formed by the hydrogen-bonded components.

Upon ozonolysis this copolymer yields succinic acid, succindialdehyde and dicarboxylic acids containing several MMA residues. The percentage of butadiene (9.2%) recovered as succinic acid and succindialdehyde provided a measure of the 1,4-butadiene-l,4-butadiene linkages in the copolymers, and the percentage of MMA units (51%) recovered as trimethyl 2-methyl-butane-l,2,4-tricarboxylate (4) n = 1, provided a measure of the MMA units in the middle of butadiene-methacrylate-butadiene triads. 

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