Carbonyl Compounds

Carbohydrates
 Elmhurst College
Synthesis - Aldehydes/Acids Reduction  Synthesis - Acetals  Chemistry Department
Synthesis - Ketones Synthesis - Hemiacetals  Virtual ChemBook

 GENERAL EQUATION: OXIDATION OF PRIMARY ALCOHOLS

primary alcohol + (0) --> aldehyde + HOH

reducing agent oxidizing agent

Synthesis of Aldehydes and Acids

 

Synthesis of Aldehydes - Oxidation of Primary Alcohols:

Aldehydes and ketones are synthesized by the oxidation of various kinds of alcohols.

The definitions which are used in inorganic chemistry involving the gain or loss of electrons; or the increase or decrease in oxidation numbers are not very useful in organic chemistry. In organic chemistry, although changes in electrons are important, oxidation and reduction is more readily observed from changes in the number of hydrogen or oxygen atoms. The definitions are as follows:

OXIDATION: loss of hydrogen, gain in oxygen, or loss of electrons

REDUCTION: gain of hydrogen, loss of oxygen, or gain of electrons.

The oxidation of primary alcohols yields aldehydes and acids if carried to completion. In the oxidation of an alcohol, the oxidizing agent, usually represented by (0), removes the hydrogen and electrons from the alcohol, the reducing agent. The "0" in the oxidizing agent is some unspecified oxygen atom which reacts with the hydrogen atoms to form water.

Synthesis of an Aldehyde:

 

Example:

1) The hydrogen on the carbon is removed along with 2 electrons.
2) The hydrogen is removed from the oxygen as Hydrogen ion.
3) The two electrons which were bonded to hydrogen are used to form the double bond.
4) The H with 2 electrons, the hydrogen ion, and O (oxygen) from the oxidizing agent form a water molecule.

 Synthesis of an Acid from an Aldehyde:

The oxidation of a primary alcohol is carried out with a strong oxidizing agent, an aldehyde is produced.
The aldehyde immediately continues to be oxidized to an acid.
The oxidation of an aldehyde to an acid is a case where oxygen is added to the reducing agent (aldehyde).
The reaction appears to occur by the insertion of the oxygen between the carbon and the hydrogen.

Health Effects of Alcohol and Aldehyde Oxidations:

When a person ingests alcohol, the reactions listed below occur in the liver with the aid of enzymes. The accumulation of acetaldehyde may produce nausea. Eventually, the acetaldehyde is converted to acetic acid which can be further metabolized without any problem.

Ethanol is oxidized to ethanal (acetaldehyde - common name)
Ethanl is oxidized to ethanoic acid (acetic acid)

 

 Health Effects of Methanol Poisoning:

If methanol is ingested, it acts as a poison because it is metabolized by oxidizing enzymes in the liver to form methanal or formaldehyde. Formaldehyde causes protoplasm in cells to coagulate. In addition, this reaction causes the lenses of the eyes to become opaque. In these ways, methanol poisoning can lead to blindness and death.