Problem 89 - Chemistry and Chemical Reactivity

Question

Identify the reaction products and write an equation for the following reactions of \(\mathrm{CH}_{2}=\mathrm{CHCH}_{2} \mathrm{OH}\) (a) \(\mathrm{H}_{2}\) (hydrogenation, in the presence of a catalyst) (b) oxidation (excess oxidizing agent) (c) addition polymerization (d) ester formation, using acetic acid

Step-by-Step Solution

Answer

(a) Propanol, (b) Acrylic acid, (c) Polymeric chains, (d) Allyl acetate.

Step 1: Hydrogenation Reaction

The hydrogenation reaction involves the addition of hydrogen (\(\mathrm{H}_2\)) across the double bond of an alkene. For the given compound \(\mathrm{CH}_2=\mathrm{CHCH}_2\mathrm{OH}\), in the presence of a catalyst like Ni, the double bond will be saturated, converting it into an alkane.Reaction: \[\mathrm{CH}_2=\mathrm{CHCH}_2\mathrm{OH} + \mathrm{H}_2 \xrightarrow{\text{catalyst}} \mathrm{CH}_3\mathrm{CH}_2\mathrm{CH}_2\mathrm{OH}\]The product is propanol.

Step 2: Oxidation Reaction

The oxidation of \(\mathrm{CH}_2=\mathrm{CHCH}_2\mathrm{OH}\) involves using an excess of oxidizing agent to fully oxidize the primary alcohol to a carboxylic acid. This occurs in two stages: the primary alcohol is first oxidized to an aldehyde, then to an acid.Reaction:\[\mathrm{CH}_2=\mathrm{CHCH}_2\mathrm{OH} \rightarrow \mathrm{CH}_2=\mathrm{CHCH}=\mathrm{O} \xrightarrow{[O]} \mathrm{CH}_2=\mathrm{CHCOOH}\]The product is acrylic acid.

Step 3: Addition Polymerization

Addition polymerization of alkenes involves the repeated formation of long chain polymers. The \(\mathrm{CH}_2=\mathrm{CHCH}_2\mathrm{OH}\) can polymerize under certain conditions to form poly(ethylene glycol) derivatives by opening the double bonds and forming chains.Equation:\[\text{n }\mathrm{CH}_2=\mathrm{CHCH}_2\mathrm{OH} \rightarrow [-\mathrm{CH}_2-\mathrm{CHCH}_2\mathrm{OH}-]_n\]The product is a polymer with repeating \(\mathrm{CH}_2\mathrm{CHCH}_2\mathrm{OH}\) units.

Step 4: Ester Formation Reaction

Ester formation involves reacting an alcohol with a carboxylic acid like acetic acid. The \(\mathrm{CH}_2=\mathrm{CHCH}_2\mathrm{OH}\) reacts with acetic acid to form an ester and water.Reaction:\[\mathrm{CH}_2=\mathrm{CHCH}_2\mathrm{OH} + \mathrm{CH}_3\mathrm{COOH} \rightarrow \mathrm{CH}_2=\mathrm{CHCH}_2\mathrm{OOCCH}_3 + \mathrm{H}_2\mathrm{O}\]The product is allyl acetate.

Key Concepts

Hydrogenation

Hydrogenation is a chemical reaction where hydrogen (\(\mathrm{H}_2\)) is added to compounds. This typically occurs in organic molecules with double or triple bonds. These bonds become saturated when hydrogen atoms are added.
In the given reaction, (\(\mathrm{CH}_2=\mathrm{CHCH}_2\mathrm{OH}\)) undergoes hydrogenation in the presence of a catalyst. The catalyst, often nickel (Ni), aids in breaking the double bond.

• The double bond between the carbons is broken.
• Hydrogen atoms fill the open spots in the molecule.

As a result, the compound is converted into an alkane, which is a single-bonded, saturated hydrocarbon. For this reaction, the product is propanol, \(\mathrm{CH}_3\mathrm{CH}_2\mathrm{CH}_2\mathrm{OH}\), which is a saturated alcohol. Hydrogenation is important in making unsaturated fats from oils, turning them into saturated fats, which are solid at room temperature.

Oxidation of Alcohols

Oxidation of alcohols involves the transformation of an alcohol into different compounds, based on the extent of oxidation. Primary alcohols like (\(\mathrm{CH}_2=\mathrm{CHCH}_2\mathrm{OH}\)) are of particular interest here. When oxidized with an excess of oxidizing agent:

• The alcohol is first converted to an aldehyde.
• Further oxidation converts the aldehyde into a carboxylic acid.

This stepwise oxidation changes the chemical structure significantly. In the case of our reaction:

• First, \(\mathrm{CH}_2=\mathrm{CHCH}_2\mathrm{OH}\) becomes \(\mathrm{CH}_2=\mathrm{CHCHO}\) (an aldehyde).
• Then, further oxidation gives us acrylic acid, \(\mathrm{CH}_2=\mathrm{CHCOOH}\).

Acrylic acid is a key monomer used in polymer production. Understanding this oxidizing process is vital for chemical syntheses and industrial applications in producing plastics and resins.

Addition Polymerization

Addition polymerization is a process where small molecules, known as monomers, join together to form long chain polymers without the loss of any molecule. This type of polymerization is common in alkenes, like (\(\mathrm{CH}_2=\mathrm{CHCH}_2\mathrm{OH}\)).

• The double bonds in the monomers open up during the reaction.
• Monomers link together forming long, repeating chains.

In the exercise, the monomer \(\mathrm{CH}_2=\mathrm{CHCH}_2\mathrm{OH}\) polymerizes to form a polymer with a repeating structure, \([-\mathrm{CH}_2-\mathrm{CHCH}_2\mathrm{OH}-]_n\).This type of reaction is crucial in creating materials such as plastics. Polymers like these are used commonly in items like packaging materials and textiles. The versatility and strength of polymers made through addition polymerization highlight their significance in everyday products.

Esterification

Esterification is a process of forming an ester from an alcohol and a carboxylic acid. This reaction typically produces water as a byproduct. The reaction between (\(\mathrm{CH}_2=\mathrm{CHCH}_2\mathrm{OH}\)) and acetic acid is a classic example of this process.

• The hydroxyl group (\(\mathrm{OH}\)) from the alcohol and the hydrogen from the acid's carboxyl group (\(\mathrm{COOH}\)) bond to form water.
• The remaining acid and alcohol components join to form an ester.

For this exercise, the result of the esterification of (\(\mathrm{CH}_2=\mathrm{CHCH}_2\mathrm{OH}\)) with acetic acid is the formation of allyl acetate, (\(\mathrm{CH}_2=\mathrm{CHCH}_2\mathrm{OOCCH}_3\)).This reaction is fundamental in the production of flavors and fragrances in various industries. Esters have distinctive smells and are important in the natural and artificial creation of scents and tastes.