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acid ete, but particularly important for our purpose are the three 
pairs of ea-dialkyl-substituted glutaconic acids (ae-di-Me-, eap- and 
aay-tri-Me-acid), which are fully described in the literature ; for here 
is wanting the mobile hydrogen atom of the methylene group and 
therefore nothing but genuine cis-frans-isomerism is possible. 
a. Physical properties. 
1. Melting point. 
Glutaconie acid melts completely undecomposed at 1386—138°; not 
before += 180° a slight decomposition sets in. From the situation of 
the melting point we can deduce nothing, for as shown from the 
subjoined table, the melting points of the cvs-trans-isomeric gluta- 
conic acids (contrary to those of the fumarie and maleic acids) 
Cis Trans 
zz-dimethylglutaconic acid 134 — 135° 1722 
zz3-trimethyl __,, on 133° 14g° 
any 125° 150° 
differ comparatively but little. On the other hand cis-aag- and aay- 
trimethylglutaconic acid melt with elimination of water *), also the 
mono-alkyl-maleic acids *), whereas the maleic acid itself commences 
to decompose already a few degrees above its melting point (into 
anhydride, water and fumaric acid). 
2. Solubility. 
As far as solubility in different media is concerned, glutaconic 
acid behaves almost like its c/s-homologues. Not altogether so, 
however, for whereas the latter are, for instance, hardly soluble 
in concentrated hydrochloric acid (also because a transformation into 
trans-acid may occur here) the glutaconie acid is readily soluble 
therein; the cis-aa and -eay-alkylsubstituted acids are also readily 
soluble in benzene and chloroform ®, which is not the case with 
glutaconie acid itself. 
U) Perkin and THorRPE: Soc. 71. 1182 (1897); PERKIN and StH: Soc. 85 
155 (1904). As to the zz-acid, nothing is said as to the elimination of water 
2) In the solid condition the dialkylmaleic acids are only known in the form of 
anhydrides. 
3) Perkin and SMITH: Soc. 83. 8 (1903); 85. 155 (1904). 
