(a) The resonance structures shown in part (a) of Fig. P22.76 can be written for an ,-unsaturated...

(a) The resonance structures shown in part (a) of Fig. P22.76 can be written for an α,β-unsaturated carboxylic acid. Would this type of resonance interaction increase or diminish the acidity of an α,β- unsaturated carboxylic acid relative to that of an ordinary carboxylic acid? Explain.

(b) Consider the pK_a data given in part (b) of Fig. P22.76. Show how these data are consistent with both the polar effect of the double bond and the resonance effect in part (a).

Transcribed Image Text:

(b) :0: -CH-CH₁_ R-CH=CH-C-OH HỌC=CH–CH,—COH pK₂ = 4.37 Figure P22.76 H₂C H :ÖF T R-CH-CH=C-OH_ C=C + H CO₂H pK₂ = 4.70 CH3CH₂CH₂-CO₂H pK₂ = 4.87