`HCHO` and `CH_(3)-overset(O)overset(||)C-overset(O)overset(||)C-H` are the products obtained on ozonolysis of a monomer `(A)` of a polymer.
(a) Give the structure of (A)
(b) Draw the all "cls" form of a polymer of a monomer (A)

Answer

To solve the problem, we need to determine the structure of the monomer (A) based on the products obtained from its ozonolysis and then draw the cis form of the polymer derived from this monomer.

### Step-by-Step Solution:

**(a) Determine the structure of monomer (A)**

1. **Identify the products of ozonolysis**: The products given are HCHO (formaldehyde) and CH3C(=O)C(=O)H (a diketone).

2. **Analyze the ozonolysis reaction**: Ozonolysis typically cleaves double bonds in alkenes to form carbonyl compounds. The presence of formaldehyde suggests that the double bond in the monomer must be adjacent to a carbon that can yield formaldehyde upon cleavage.

3. **Propose a structure for (A)**: The simplest structure that can yield both products upon ozonolysis is isoprene (2-methyl-1,3-butadiene):
\[ \text{Structure of A (Isoprene)}: \quad H_2C=CH-C(CH_3)=CH_2 \]
This structure has a double bond that can be cleaved to produce the specified products.

**(b) Draw the cis form of the polymer of monomer (A)**

1. **Understand the polymerization of isoprene**: Isoprene polymerizes to form natural rubber, where the repeating unit is isoprene itself.

2. **Draw the cis form of the polymer**: The polymer will consist of repeating units of isoprene, maintaining the cis configuration around the double bonds. The structure can be represented as follows:
\[ \text{Cis polymer structure:} \]
\[ \text{(Cis-Polyisoprene)}: \quad \text{-(CH_2-C(CH_3)=CH-CH_2-)}_n \]
In this structure, the double bonds are in the cis configuration, which is characteristic of natural rubber.

### Final Answer:
(a) The structure of monomer (A) is isoprene: \( H_2C=CH-C(CH_3)=CH_2 \).

(b) The cis form of the polymer of monomer (A) is represented as:
\[ \text{-(CH_2-C(CH_3)=CH-CH_2-)}_n \]