Q22.60CP - Chemistry: Molecular Nature Of Matter And Change

Question

A major use of ${\text{Cl}}_{\text{2}}$  is in the manufacture of vinyl chloride, the monomer of poly (vinyl chloride). The two-step sequence for formation of vinyl chloride is depicted below.

(a) Write a balanced equation for each step. 

(b) Write the overall equation. 

(c) What type of organic reaction is shown in step  1? 

(d) What type of organic reaction is shown in step  2? 

(e) If each molecule depicted in the initial reaction mixture represents 0.15 mol of substance, what mass (in $g$ ) of vinyl chloride forms?

Step-by-Step Solution

Answer

(a) The balanced equation for each step is -

 $C{l}_2\left(g\right)+H_{2}C=C{H}_2\left(g\right)\to C{H}_{2}Cl-C{H}_{2}Cl\left(g\right)$

 ${\text{CH}}_{\text{2}}{\text{Cl - CH}}_{\text{2}}\text{Cl(g)}\to {\text{CH}}_{\text{2}}\text{ - CHCl(g) + H - Cl(g)}$

(b) The overall reaction is –

 ${\text{Cl}}_{\text{2}}\text{(g) + HC = CH(g)}\to {\text{CH}}_{\text{2}}\text{ - CHCl(g) + H - Cl(g)}$

(c) The organic reaction shown in step one is electrophilic addition reaction.

(d) The organic reaction shown in step two is elimination reaction.

(e) The mass of vinyl chloride forms is $\text{28.125 g}$ .

Step 1: Concept Introduction

A chemical process can occur in the presence of different components. A mathematical representation of this process is known as chemical equation. A balanced chemical equation is one in which the number of atoms in all molecules is the same on both sides of the equation.

Step 2: Balance Equation

(a) 

Looking at the picture given, assuming that green atoms-represent  $\text{Cl}$, blue-H , and black-C , then initially the following molecules are present: ${\text{Cl}}_{\text{2}}$ , chlorine gas-depicted as a green molecule made of two $\text{Cl}$  atoms, and ${\text{C}}_{\text{2}}{\text{H}}_{\text{4}}$ , ethene-depicted as another molecule. Upon a reaction  (1), the following conversion occurs to produce $\text{1,1 - }$ dichloroethane –

 ${\text{Cl}}_{\text{2}}{\text{(g) + H}}_{\text{2}}{\text{C = CH}}_{\text{2}}\text{(g)}\to {\text{CH}}_{\text{2}}{\text{Cl - CH}}_{\text{2}}\text{Cl(g)}$

Then, upon rearrangement, the monomer of poly (vinyl chloride) is formed –

 ${\text{CH}}_{\text{2}}{\text{Cl - CH}}_{\text{2}}\text{Cl(g)}\to {\text{CH}}_{\text{2}}\text{ - CHCl(g) + H - Cl(g)}$

Step 3: The Overall Reaction

(b)

The overall reaction can then be written as –

 ${\text{Cl}}_{\text{2}}\text{(g) + HC = CH(g)}\to {\text{CH}}_{\text{2}}\text{ - CHCl(g) + H - Cl(g)}$

Step 4: Organic Reaction in First Step

(c)

The reaction shown in step  1, is an electrophilic addition reaction as two species are combined to form one.

Therefore, the reaction is electrophilic addition reaction.

Step 5: Organic Reaction in Second Step

(d)

The reaction shown in step 2 , is an elimination reaction, as $\text{HCl}$  is eliminated from ${\text{CH}}_{\text{2}}{\text{Cl - CH}}_{\text{2}}\text{Cl}$  .

Therefore, the reaction is elimination reaction.

Step 6: Mass of Vinyl Chloride

(e)

Based on the overall reaction, since there are  3 molecules of  ${\text{Cl}}_{\text{2}}$ and  ${\text{CH}}_{\text{2}}{\text{ = CH}}_{\text{2}}$ initially, meaning that –

 $n\left(C{l}_2\right)=n\left(C{H}_2=C{H}_2\right)=3\times 0.15 mol=0.45 mol$

The amount of vinyl chloride ( ${\text{CH}}_{\text{2}}\text{ - CHCl}$) produced is then –

 $$\begin{gathered} n\left(CH{H}_2-CHCl\right)=0.45 mol \\ m\left(C{H}_2-CHCl\right)=n·M_R \\ =0.45 mol·62.50 g/mol \\ m\left(C{H}_2-CHCl\right)=28.125g \end{gathered}$$

Therefore, the value for mass is obtained as  $\text{28.125 g}$.