CHEMICAL PROPERTIES 289 



affinity of the hydrogen-bonded carboxylate group for protons would be 

 lessened and account for the low p^^^. This anion would also derive addi- 

 tional stability from resonance between structures (II) to (V), and this 

 would diminish the tendency for loss of a second proton, accounting for 

 the high pK^^. Such hydrogen bonding would, of course, not occur in fumaric 



S ?i f! 



c c c 



HC^ "^O HC-^ ^O HC-^ ^O 



II >^ II Ji II ;. 



Y 



HC^ /O HC. O HC^ /6 



^c-^ ^C^ 



II I- 



OH O O 



(I) (n) (ni) 



(IV) (V) (VI) 



acid. Davison (1953) believed, on the other hand, that the hydrogen bond 

 would not survive competition from water molecules, and stated that pre- 

 liminary infrared data showed no bands indicating hydrogen bonding in 

 solution. However, Card well et al. (1953) found infrared bands suggestive 

 of a hydrogen bond in H-maleate*, the bond being more symmetrical in 

 the ion than in maleic acid, so that structure (VI) might be more appro- 

 priate. The dissociation of the first proton would cause the second proton 

 to move into a more symmetrical position. McDaniel and Brown (1953) 

 also provided evidence that the hydrogen bond may well be retained in 

 solution. Nash (1953) felt that the presence of a hydrogen bond in H-mal- 

 eate~ would decrease the symmetry and resonance of the molecule, and 

 that this would oppose the formation of the hydrogen bond. Instead, he 

 postulated that the proton exists within the molecule: 



O" 



I 



