Dibromomaleic acid

Dibromomaleic acid [608-37-7] M 273.9, m 123.5°, 125°dec. It has been recrystd from Et2O or Et2O-CHCl3. It is slightly soluble in H2O, soluble also in AcOH but insoluble in C6H6 and CHCI3. [Salmony and Simonis B 38 2583 1905-, Ruggli HCA 3 566 7929]. 

Electrolysis of 1,2-dibromofumaric and 1,2-dibromomaleic acid or the diesters produces a 90-100% yield of acetylenedicarboxylic acid or diester 302). For vie-dihalides with no radical or anion stabilizing group in the a position an E2B like elimination mechanism is strongly indicated, /.e., 2e-transfer and double bond formation in a synchronous process (Eq. (148)). 

C4H2Br204 dibromomaleic acid 608-37-7 25.00 2.3371 2 2581 C4H4N2S3 ethylene thiuram monosulfide 33813-20-6 25.00 1.4786 2... 

Malonic acid ) Citric acid Maleic acid Malic acid Bromomalic acid f Dibromomalic acid Acetylenedicarboxylic acid Acyclic and cyclic ketones Phenol, aniline and derivatives Tartaric acid/Acetone Oxalic acid or Glyoxalic acid Ce(III, IV) Zhabotinskii (Original) [Kasperek Bruice (1971)] [Beck Varady Mag Chem Foly 81 (1975) 519] [Stroot Janjic Helv Chim Acta 58 (1976) 116] [Orban Koros J. Phys. Chem. 82 (1978) 1672] [Rastogi et al. Aachen Meeting (1979) 98-107] [Nosticzius Bodiss J. Am. Chem. Soc. 101 (1979) 3177]... 

Such a process would always lead to the formation of the cis isomer, whereas it is known that treatment of acetylenedicarboxylic acid HOOGCsGGOOH with bromine gives dibromomaleic and dibromofumaric acids, the cis and trans forms respectively. The formation of the dibromofumaric acid is more favoured from energy considerations, since the molecule is stabilized by the formation of two hydrogen bonds with the bromine atoms (for hydrogen bond formation between the hydrogen of a carboxyl group and a bromine atom, see Chapter 12). 

Dibromoethylene, cis and tranSy MA photochemical adducts, 189 Dibromomaleic anhydride applications, 63 synthesis route, 61 Dibromomethane, 184, 187 a,/3-Dibromosuccinic acid, hydrogen bromide elimination 60... 

Elving and co-workers [39, 40] investigated the polarographic behavior of mono- anddibromosubstituted maleic andfumaric acids and their esters. Monobromomaleic acid is reduced to maleic, fumaric, and butadiene-1,2,3,4-tetracarboxylic acid, where the proportions of the products depend on the pH value. Monobromofumaric acid is reduced to fumaric acid. The esters of both acids are reduced to the esters of unsubstituted fumaric acid. Dibromomaleic and dibromofumaric acids and their esters are reduced to acetylene-dicarboxylic acid, and the half-wave potentials of the cis acid and its diethyl ester are less negative (by 0.04-0.18 and 0.10-0.12 V, respectively, depending on the pH value) than the half-wave potentials of the trans compounds. 

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