Study the reaction scheme and answer the questions below - Leaving Cert Chemistry - Question 8 - 2020

In conversion 1, the reagent used is hydrogen ($H_2$) and the catalyst can be nickel ($Ni$), palladium ($Pd$), or platinum ($Pt$).

The structure of ethanol is as follows:

    H   H
    |   |
H - C - C - O - H
    |   |
    H   H

In conversion 1, the bonds formed include:

• The C-H bonds are created when hydrogen is added to the carbon atoms.
• The C-O bond is present in the ethanol structure.

The organic substance that is highly soluble in water is ethanol ($C_2H_5OH$). This is due to the presence of the hydroxyl ($-OH$) group which can form hydrogen bonds with water molecules, enhancing its solubility.

Compound X is identified as chloroethene (monochloroethene or vinyl chloride, $C_2H_3Cl$).

During conversion 7, the geometry changes from trigonal planar around the carbon atom in chloroethene to tetrahedral when it converts to ethane, following the saturation of the double bond.

The repeating unit of polyvinyl chloride (PVC) can be represented as:

   Cl   H   H   H
    |    |    |  
--C--C--C--C--
   |   |  |   |
   H   H   Cl   Cl

where the structure consists of alternating carbon atoms, with chlorine atoms attached, representing the polymer's repeating unit.

In conversion 6, the mechanism involves the following steps:

1. Initiation: Chlorine ($Cl_2$) undergoes heterolytic fission to form two chloride ions ($Cl^-$).
2. Formation of Carbocation: The carbon atom adjacent to the chlorine will form a carbocation ($C^+$) as the double bond breaks.
3. Nucleophilic attack: The $Cl^-$ ion attacks the carbocation, resulting in the formation of the final product.
   This mechanism illustrates the importance of ionic species in facilitating organic reactions.