Problem 65 - Chemistry Matter and Change

Question

Draw structures of and supply names for the organic compounds produced by reacting ethene with each of the following substances. \begin{equation} \begin{array}{ll}{\text { a. water }} & {\text { c. hydrogen chloride }} \\\ {\text { b. hydrogen }} & {\text { d. fluorine }}\end{array} \end{equation}

Step-by-Step Solution

Answer

The products are ethanol, ethane, chloroethane, and 1,2-difluoroethane.

Step 1: Reaction of Ethene with Water

When ethene \((C_2H_4)\) reacts with water in the presence of an acid catalyst, it undergoes hydration to form ethanol. The reaction can be represented as: \\[ C_2H_4 + H_2O \rightarrow C_2H_5OH \\text{(Ethanol)} \] The -OH group adds to one of the carbon atoms, forming ethanol.

Step 2: Reaction of Ethene with Hydrogen

Ethene \((C_2H_4)\) reacts with hydrogen gas in the presence of a metal catalyst (such as palladium or nickel) to undergo hydrogenation, resulting in the formation of ethane. The reaction is: \\[ C_2H_4 + H_2 \rightarrow C_2H_6 \\text{(Ethane)} \] The hydrogen molecules add across the double bond, converting it into a single bond.

Step 3: Reaction of Ethene with Hydrogen Chloride

When ethene \((C_2H_4)\) reacts with hydrogen chloride, it undergoes an addition reaction to form chloroethane. The reaction is: \\[ C_2H_4 + HCl \rightarrow C_2H_5Cl \\text{(Chloroethane)} \] The H and Cl atoms add across the double bond on the ethene molecule, forming a saturated compound.

Step 4: Reaction of Ethene with Fluorine

Ethene \((C_2H_4)\) reacts with fluorine in a highly exothermic reaction to form 1,2-difluoroethane. The reaction is: \\[ C_2H_4 + F_2 \rightarrow C_2H_4F_2 \\text{(1,2-Difluoroethane)} \] Here, two fluorine atoms add across the double bond of ethene to form a saturated ethane derivative.

Key Concepts

Hydration Reaction

A hydration reaction involves the addition of water to a compound. When ethene \((C_2H_4)\) undergoes hydration, it reacts with water \((H_2O)\) in the presence of an acid catalyst to form ethanol \((C_2H_5OH)\). This reaction adds an -OH group to one of ethene's carbon atoms.
The process can be summarized as follows:

• Ethene engages with water.
• The role of the catalyst is essential as it accelerates this process.
• As a result, ethanol, a type of alcohol, is produced.

A hydration reaction is a type of addition reaction where molecules combine, and it plays a critical role in organic chemistry for converting alkenes into alcohols.

Hydrogenation

Hydrogenation is the process where hydrogen \((H_2)\) is added to a compound. In the reaction involving ethene \((C_2H_4)\), hydrogen reacts with ethene in the presence of a catalyst like palladium or nickel to produce ethane \((C_2H_6)\). During this, the double bond in ethene is converted into a single bond, saturating the molecule.
The steps in hydrogenation include:

• Ethene is exposed to hydrogen gas.
• A metal catalyst such as nickel helps facilitate the reaction.
• The reaction results in a saturated hydrocarbon, ethane.

Hydrogenation is widely used in the food industry to solidify vegetable oils, forming saturated fats. It's a crucial process for converting unsaturated compounds to their saturated counterparts as in the production of margarine.

Addition Reaction

An addition reaction involves the adding of atoms to a molecule, typically at double or triple bonds. In the context of ethene \((C_2H_4)\), different substances can add across its double bond. For example, hydrogen chloride \((HCl)\) adds to ethene forming chloroethane \((C_2H_5Cl)\).
Here's how an addition reaction generally proceeds:

• Molecules like hydrogen chloride target the double bond.
• The "+" and "-" ends of chemicals interact with the double bond to form new compounds.
• The resulting compound is more saturated than the original.

Addition reactions are fundamental in organic synthesis for building larger, more complex molecules.

Saturated Compounds

Saturated compounds are hydrocarbons where all carbon-carbon bonds are single, containing the maximum number of hydrogen atoms possible. In reactions such as ethene \((C_2H_4)\) with fluorine \((F_2)\), the addition across the double bond results in a saturated product. This converts the double bond into single bonds, which is a hallmark of saturation.
Characteristics of saturated compounds include:

• Stability due to single bonds.
• No reaction with reagents that target double bonds.
• Often used in fuels due to their stability and high energy content.

Saturated compounds are crucial in industries, serving as a key element in the formulation of many synthetic materials like plastics.