Question

The letters A, B, C, D, and E represent isomeric cyclobutane dicarboxylic acid, one of them being a racemic form. It was shown that: 

(a) only compound C forms a cyclic anhydride easily, 

(b) B yields an cyclic anhydride only at higher temperatures, 

(c) of all the acids under investigation, only A releases carbon dioxide when heated, 

(d) D and E do not change at higher temperatures, 

(e) 2 moles of diethyl ester of malonic acid when reacted with sodium ethoxide (EtONa), are transformed to sodium salt which by reaction with methylene iodide (CH₂I₂) yields a tetraester C₁₅H₂₄O_8. This new ester gives a tetraester C₁₆H₂₄O₈ in the reaction with 2 moles of sodium ethoxide and 1 mole of methylene iodide. The last mentioned tetraester is transformed by alkaline hydrolysis and subsequent acidification to a tetracarboxylic acid which when heated, gives a mixture of B and E. 

Give formulas corresponding to the letters A, B, C, D, and E. Mark the group which is above the plane of the cycle, that under the plane with

For example: 

2. Express processes a), b), and c) by chemical equations.

Answer 1

The chemical equations.