Maleic acid crystal structure

This intramolecular bonding in maleic acid, (8), halves its ability to form intermolecular bonds. In fumaric acid, on the other hand, all of the hydrogen bonds form between molecules (intermolecular bonds) to give a stronger, interlinked crystal structure. 

The pH dependence of the rate of modification shows that the pKa of Asp-32 is less than 3.165 It is seen in the high-resolution crystal structures that the carboxyl groups of the two aspartate residues are hydrogen-bonded to each other. This is similar to the ionization of maleic acid, which has pKa values of 1.9 and 6.2 (equation 16.30). 

M. Shahat. Acta Cryst. 5, 763 (1952). x-ray crystal structure of maleic acid. 

Maleic and fumaric acids (HOOC-CH = CH-COOH) have almost the same length of carbon chain as succinic acid, but their geometry is influenced by the presence of the double bond in the carbon chain. The crystal structure of... 

Molybdenum(VI) complexes citric acid, 476 IR spectra, 469 guanidine, 283 hydroxamic adds, 506 maleic add, 475 conformation, 467 crystal structure, 476 tartaric add, 479 NMR, 468... 

Photograph 9-25 Alite crystal with attached alkali sulfates. Lamellar structure in belite revealed in upper right corner. 30-min maleic acid etch on crushed, sieved clinker. (S A6748)... 

Neocarzinostatin 301, first reported by Ishida and coworkers in 1965, is produced by S. carzinostaticus ATCC 15994 and is a 1 1 noncovalently associated mixture of a protein component, apoprotein, and a chromophoric molecule [297]. The mixture was separated somewhat later into its component parts and eventually characterized structurally. The chromophoric component was shown in 1985 to have the nine-membered polyeneyne skeleton 301 [298]. The apoprotein has been characterized as a 113 amino acid polypeptide based upon the gene base sequence and apoprotein crystal structure [299, 300]. The three-dimensional solution structure of intact neocarzinostatin was determined using 2D NMR techniques [301], and the crystal structure of holo-neocarzinostatin was reported in the same year [302]. The antibiotic 301 showed potent antitumor activity against a wide range of tumors and a poly(styrene-co-maleic acid)-301 conjugate was approved in Japan and has been marketed for use against hepatoma since 1994 [303]. 

Figure 3.17 (Top) Crystal structure of maleic acid, 137 displaying both inter- and intramolecular hydrogen bonding. (Bottom) Experimental and spectral fitting MAS spectra of maleic acid at 14.1 T.

Polymorphism is possible for any compound, but Ihe conditions under which these polymorphs are stable may be difficult to know a priori. McCrone stated almost half a century ago that the number of forms known for a given compound is proportional to the time and money spent in research on that componnd and this statement is turning out to be truer than ever. Componnds formerly believed to exist in a single form are yielding a second or even a third polymorph. For example, novel polymorphs of aspirin, maleic acid, and 1,3,5-trinitrobenzene, have been fonnd after several decades of their first crystal structure being reported. Polymorphism is not as widespread in terms... 

One of the best ways to grow new polymorphs of a given substance is by diversifying crystallization experiments. Several examples wherein attempted co-crystallization of two compounds resulted in the serendipitous crystallization of a new polymorph of one of the components have been reported in the recent literature. New polymorphs of aspirin and maleic acid, ° trinitrobenzene, and four polymorphs of benzidine " were unexpectedly obtained during attempted co-crystallization experiments. In contrast to the well-understood role of structurally related tailor-made additives, the selective growth of a particular polymorph during attempted co-crystallization experiments is difficult to explain because the components have different molecular structures and complementary functional groups. However, the technique has shown early promise in the discovery... 

---