Oxidation, Reduction, Condensation, and Hydrolysis

In Topics 1-7, you learned about all of the organic families that comprise organic compounds. In the Topic 8 and 9, we will focus on the reactions that result in the formation of these compounds and their practical applications.

Upon completion of Topic 8 and 9, you will be able to:

• • describe different types of organic reactions

  • predict and correctly name the products of organic reactions

Millions of reactions take place everyday in the trillions of cells in your body. Since living organisms are composed of organic compounds, many of the reactions we will discuss in this lesson also occur in the cells of your body.

Reactions of Organic Compounds (Part 2)

• Reactions that involve the gain of oxygen or a loss of hydrogen.

• Oxygen atoms are supplied by oxidizing agents such as hydrogen peroxide (), potassium dichromate (), and potassium permanganate ().

• Oxidation reactions are under acidic conditions with an acid as a catalyst, usually concentrated sulfuric acid, ().

• The symbol [O] is often used to represent the oxidizing agent in a chemical equation.

• Essentially, the reactive [O] removes two hydrogen atoms: one from the -OH group and ne from the adjacent C atom, resulting in a C=O group; a water molecule is also produced.

• • When a primary alcohol is oxidized (mildly), an aldehyde is formed.

• • If the aldehyde is further oxidized, a carboxylic acid is formed.

• • When a secondary alcohol is oxidized, a ketone forms.

• • When a tertiary alcohol is reacted with an oxidizing agent, no oxidation reaction occurs.

  • Tertiary alcohols do not oxidize because no H atom is available on an adjacent carbon atom.

• The C=O bond in aldehydes and ketones can undergo an addition reaction with hydrogen, but not other reactants.

• High temperatures and pressures and the presence of a catalyst are required.

• Can be considered the reverse of the oxidation of alcohols.

• • When an aldehyde is reduced, a primary alcohol is formed.

  • Note, this is the opposite of the oxidation of a primary alcohol.

• • When a ketone is reduced, a secondary alcohol is formed.

  • Note, this is the opposite of the oxidation of a secondary alcohol.

• • When a carboxylic acid is reduced, an aldehyde is formed.

  • Note, this is the opposite of the oxidation of an aldehyde.

  • If the aldehyde is further reduced, it will produce a primary alcohol, such as in example i).

• Two molecules combine to form a larger product, with the elimination of a small molecule such as water or an alcohol.

• This reaction is catalyzed by concentrated sulfuric acid and may require heat.

• Can also be considered a dehydration reaction because a water molecule is formed.

• • When two alcohols react with one another, a water molecule is removed.

  • A -H from one alcohol, and a -OH from the other alcohol are removed.

  • The two remaining compounds join at the -O- to form an ether.

• • When a carboxylic acid reacts with an alcohol, a water molecule is removed.

  • A -H from the carboxylic acid, and the -OH the alcohol are removed.

  • The remaining compounds join at the -O- and form an ester.

  • This is also called an esterification reaction.

• • When a carboxylic acid reacts with an amide, a water molecule is removed.

  • The -OH from the carboxylic acid, and the -H from the terminal -NH₂ on the amine are removed.

  • The remaining compounds join at the intersection of the now unbonded carbon of the carboxylic acid and the -NH of the amine.

• Water is added to a molecule. This splits the bond in two and creates two product molecules.

• This is the reverse of a condensation reaction.

• • When an ester reacts with water, the molecule splits at the -O-. The part of the chain that contained the C=O will retain the oxygen. A hydrogen from the water molecule (HOH), will bond to form a carboxylic acid.

  • The OH from the water molecule (HOH), will bond to the other chain and form an alcohol.

• • When an ether reacts with water, a split occurs at one end of the -O-. The chain that retained the -O will receive a -H from the water molecule (HOH).

  • The chain that did not retain the -O will receive the -OH from the water molecule (HOH).

  • The two resulting products are alcohols.

• • When an amide reacts with water, a split occurs between the C-N.

  • The chain that includes the C=O will bond to the -OH of the water molecule (HOH). The resulting product is a carboxylic acid.

  • The chain that includes the -NH, will bond with the -H of the water molecule (HOH) forming -NH₂, and thus, an amine.