Oxidation of Organic Compounds

Some organic compounds can be oxidized by oxidizing agents. Oxidation can be done by strong oxidizing agents and mild oxidizing agents. When oxidation occurs, Oxidation number of carbon atom or atoms is increased.

Oxidizing organic compounds

Oxidation of following organic compounds are common and should learn properly to understand organic chemistry.

• Alkene
• Alkyne
• Alcohol
• Aldehyde

Products after the oxidation

Carboxylic acids, carbon dioxide, aldehyde, ketone and more different types of organic compounds and inorganic compounds (carbon dioxide) can be given as products according to the initial organic compound, type of oxidant reagents and states.

Oxidizing agents

There are two types of oxidation agents, strong oxidizing agents and mild oxidizing agents

Strong oxidizing agents

• In acidic medium Acidic permanganate - H⁺ / MnO₄^-
• In acidic medium dichromate - H⁺ / Cr₂O₇^2-
• In acidic medium chromate - H⁺ / CrO₄^2-

Potassium or sodium can exist as the cations such as H⁺ / KMnO₄ or H⁺ / Na₂Cr₂O₇

Mild oxidizing agents

• Pyridinium chlorochromate( PCC)
• H₂O₂
• Tollens's reagent - Adding [Ag(NH₃)₂]⁺, heating,then dilute HCl and water
• Fehling's A / Fehling's B and then add dilute HCl

Which organic compounds are not easy to oxidize?

• From hydrocarbons, alkanes are difficult to oxidize than alkenes and alkynes.
• Ketone are also hard to oxidize than aldehyde. Aldehyde can be oxidized to carboxylic acid by strong oxidizing agents or mild strong oxidizing agents. But ketone cannot be.
• Carboxylic acids are not oxidized. Oxidation of some alkene, alkyne, alcohol and aldehyde compounds give carboxylic acids as a product.

Which organic compounds are oxidized?

• Alkenes and alkynes can be oxidized to alcohols, ketones, carboxylic acids and carbon dioxide.
• Alcohols can oxidized to aldehydes or ketones or carboxylic acids..
• Aldehyde can be oxidized to carboxylic acids.

Oxidation behavior of these compounds are explained in detail later in this tutorial.

Oxidation of Alkenes and Alkynes from strong oxidizing agents

The alkene or alkyne molecule is broken through the double bond or tripple bond and give ketone or carboxylic acids or carbon dioxide as products. These products will vary with the strucure of alkene or alkyne molecuule.

Ethene oxidation by acidic potassium permangonate | C₂H₄ + acidic KMnO₄

Ethene molecule is broken through the double bond and as much as oxygen atoms are combined with carbon atoms to oxidize carbon atom. Also carbon-hydrogen bonds of carbon atoms in the alkene part are broken.

So each carbon atom can keep two oxygen atoms by producing carbon dioxide.

Alcohols

The carbon - carbon bonds (C-C) of alcohol molecule are not broken while C-H bonds which are connected to the carbon atom which has the OH group are broken. See the figure.

Primary alcohols

Primary alcohols can be oxidized to aldehyde or carboxylic acids.

• PCC is used to oxidize primary alcohols to aldehyde.
• Strong oxidizing agents are used to oxidize primary alcohols to carboxylic acids.

Secondary alcohols

Secondary alcohols are oxidized to ketones by strong oxidizing agents.

Aldehyde

Oxidation number of carbonyl carbon atom is +1 in aldehydes except formaldehyde. Aldehydes are oxidized to carboxylic acids from strong oxidizing agents or mild oxidizing agents.

Formaldehyde

Carbon dioxide is given by the oxidation of formaldehyde.

Oxidation of aldehyde is used to identify aldehyde and ketone.

Alkyl benzene

Methyl benzene, ethyl benzene can be oxidized to benzoic acid. Benzaldehyde also is oxidized to benzoic acid from oxidizing agents.

Natural incidents of oxidizing organic compounds

• Oxidation of ethanol to acetic acid.