Chlorofumaric acid

Ingold (1) has mentioned that the older literature contains several observations indicating the existence of stereochemically favorable and unfavorable situations for elimination reactions leading to acetylenic compounds. For instance, Michael (2) found that chlorofumaric acid (4) is converted by alkali about 50 times faster than in chloromaleic acid (5) into acetylene dicarboxylic acid (6). Chovanne (3) has observed that cis-dichloroethylene (7) is transformed by alkali about 20 times faster than is the trans-isomer 8 into chloroacetylene (9). 

Elimination reactions, like displacement reactions, usually involve elements which are truns to each other. Thus cis 2-phcnyl-l-cyclo-hexanol (XXV) on dehydration with phosphoric acid gives principally 1-phenylcyclohexone (XXVI), but the corresponding trans alcohol (XXVII) gives mostly 3-phenylcyclohexene (XXVIIT).16 Similarly chlorofumaric acid (XXIX) is dehydrohalogenated to acetylenedicar-... 

Propylene glycol is often used as the diol. To a lesser extent, other glycols, like diethylene glycol, are also used for greater flexibility, or neopentyl glycol for a somewhat better thermal resistance. Bisphenol A (2,2 bis(4-hydroxyphenyl) propane) is used when better chemical resistance is needed. Use of mixed diols is conunon. Many unsafturated dicarboxylic acids can be used, but maleic (as an anhydride) or fumaric acids are the most common. Chloromaleic or chlorofumaric acids are also employed. 

MegCO. par. sol. CeHg, ligroin. Cold KOH —> chlorofumaric acid. Boiling aq. Na salt chloromaleic acid Na salt. ACgO at 150 — chloromaleic anhydride. 

Fumaric acid (IV), the trans-isomev of maleic acid is sometimes preferred to maleic anhydride as it is less corrosive and gives lighter-coloured products with slightly improved heat resistance. Chloromaleic acid (V) and chlorofumaric acid may be used in the production of self-extinguishing resins. 

Gomberg, Cone and Kyriakides [105] modified the method by reacting chlorofumaric acid with hot sodium phenoxide, the excess of phenol having been previously removed under vacuum. In this way, a high yield (97 per cent) of chromone-2-carboxylic acid was obtained. More recently, an improved conversion of a thiophenol to a l-thiochromone-2-carboxylic ester was achieved by Bossert [106] by condensation with 3-oxoesters (/S-keto-esters) under the influence of polyphosphoric acid (PPA). 

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