Answer 1

3,4-dihydrocyclobutane[1,2-c]furan-1,5-dione

Answer 2

The reactant is a cyclobutane derivative with a -C(COOH)3 group at one carbon and a -COOH group at an adjacent carbon. Upon heating (Δ):

1. The -C(COOH)3 group undergoes two successive decarboxylations, losing 2 molecules of CO2, to form a -CH2COOH group. Reaction: R-C(COOH)3 $\xrightarrow{\Delta}$ R-CH2COOH + 2CO2 The intermediate product is cyclobutane-1-(carboxymethyl)-2-carboxylic acid.

2. The intermediate product has a -CH2COOH group and a -COOH group on adjacent carbons of the cyclobutane ring. Upon further heating, these two carboxylic acid groups undergo intramolecular dehydration to form a cyclic anhydride. This forms a 6-membered anhydride ring fused with the cyclobutane ring.

The final product is 3,4-dihydrocyclobutane[1,2-c]furan-1,5-dione.

Structure of Reactant:

      COOH
      |
    C_ext-COOH
      |
      C1
     /  \
    C4  C2-COOH
     \  /
      C3

(Where C1, C2, C3, C4 form the cyclobutane ring, and C_ext is an external carbon attached to C1)

Structure of Intermediate after Decarboxylation:

      CH2COOH
      |
      C1
     /  \
    C4  C2-COOH
     \  /
      C3

Structure of Final Product (Anhydride):

This can also be represented as:

O=C1OC(=O)C2C(C1)C(C)C2