Consider the reaction scheme on the right - Leaving Cert Chemistry - Question 8 - 2016

Substance X is aluminium oxide / alumina / Al2O3 / concentrated sulfuric acid / H2SO4. The organic reaction type involved is elimination / dehydration.

In this conversion, the geometry around the carbon atoms changes from tetrahedral to planar due to the formation of a double bond (alkene) in ethene.

The organic reaction type is substitution.

Mechanism:

1. Initiation: Homolysis of chlorine molecule (Cl2) into free radicals, Cl•, due to ultraviolet light:

   $Cl_2 \xrightarrow{uv} 2Cl•$

2. Propagation: The chlorine radical (Cl•) reacts with ethane (C2H6), producing hydrogen chloride (HCl) and an ethyl radical (C2H5•):

   $Cl• + C_2H_6 \rightarrow HCl + C_2H_5•$

3. The ethyl radical (C2H5•) then reacts with another chlorine molecule (Cl2) to form chloroethane (C2H5Cl) and another Cl• radical:

   $C_2H_5• + Cl_2 \rightarrow C_2H_5Cl + Cl•$

4. Chain Reaction: This process repeats, propagating the reaction further until termination occurs, forming chloroethane.

Effect of Tetrabutyl Ammonium Ion: The presence of tetrabutyl ammonium ions can help to increase the rate of reaction by providing a phase transfer catalyst, which enhances the availability of chlorine radicals.

C = ethyl methanoate / ethyl formate.

Structure:

     O
     ||
H3C-C-O-CH2-CH3

In the drawing, circle the carbonyl group: O=C

The type of reaction is called base hydrolysis or saponification.