Name: alcohol oxidation reagents and products
Uploaded: 2025-05-22T09:05:35.000Z
Duration: 2 min 37 s
Channel: JoVE

As with the reduction of carbonyls to alcohols, the outcome of the oxidation of alcohols to carbonyls depends on the number of alpha protons present in the starting alcohol. Here, the oxidation state of the alpha carbon linked to the hydroxyl group is increased.
A primary alcohol has two hydrogen atoms attached to the alpha carbon atom. Hence, the molecule can be oxidized twice: first to an aldehyde, and then to a carboxylic acid. Here, the reaction is aided by Jones reagent: a chromium trioxide solution in aqueous sulfuric acid in the presence of acetone.
The mechanism of the reaction has two steps. In the first step, the alcohol and chromic acid react to form a chromate ester. Subsequently, the chromate ion leaves via an E2 pathway to form the carbon&#8722;oxygen pi bond.
The aldehyde is then hydrated and the process is repeated to generate a carboxylic acid. Similarly, the oxidation of a primary alcohol with potassium permanganate ultimately yields a carboxylic acid.
In either case, it is difficult to isolate the intermediate aldehyde. Achieving this requires a more selective reagent like pyridinium chlorochromate, or PCC.
Both Jones reagent and PCC also transform secondary alcohols i

oxidation of alcohols

Oxidation of Alcohols

In this lesson, the oxidation of alcohols is discussed in depth. The various reagents used for oxidation of primary and secondary alcohols are detailed, and their mechanism of action is provided.
The process of oxidation in a chemical reaction is observed in any of the three forms:
<ul>
	<li>(i) loss of one or more electrons,</li>
	<li>(ii) loss of hydrogen,</li>
	<li>(iii) addition of oxygen.</li>
</ul>
Oxidation is the opposite process of reduction, and hence, as carbonyls are reduced to alcohols, alcohols are oxidized to carbonyls. However, the oxidation of alcohols to carbonyls is dictated by the number of hydrogens present on the &#945;-carbon linked to the hydroxyl group in the starting alcohol. Accordingly, while primary alcohols can be oxidized to aldehydes and further carboxylic acids, the secondary alcohols can only be oxidized to their corresponding ketones. Since there are no &#945;-protons, tertiary alcohols cannot be oxidized. During the oxidation, there is a corresponding increase in the oxidation state of the central species.
<h4>Reagents and Mechanism</h4>
A popular reagent is the Jones reagent, a chromium trioxide solution in aqueous sulfuric acid in the presence of acetone. The reaction proceeds via an intermediate chromate ester and a subsequent E2 pathway to produce the carbonyl species. However, while the Jones oxidation ends at a ketone for secondary alcohol, the oxidation is repeated for primary alcohol resulting in a carboxylic acid. The other popular reagent used for oxidation is potassium permanganate. Similar to the Jones reagent, potassium permanganate is also a strong oxidizing agent converting the primary alcohol to a carboxylic acid. Hence, when an aldehyde is desired, a selective reagent like pyridinium chlorochromate or PCC should be used.
One major drawback of using these reagents is that they involve the higher oxidation states of chromium that are toxic. Accordingly, greener alternatives like Swern oxidation and Dess-martin oxidation have been designed. They employ reagents such as oxalyl chloride, dimethyl sulfoxide (DMSO), triethylamine, and dichloromethane, which are relatively non-toxic to convert the primary alcohols into aldehydes and secondary alcohols into ketones. In their mechanism, the Swern oxidation advances via an alkyl-sulfonium compound, while the Dess&#8211;Martin oxidation proceeds via a periodinane intermediate.

In this lesson, the oxidation of alcohols is discussed in depth. The various reagents used for oxidation of primary and secondary alcohols are detailed, ...

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JoVE Core

Organic Chemistry

Unit 1

Alcohols and Phenols

KEY TERMS AND CONCEPTS

alcohol oxidation reagents and products

Alcohol oxidation changes primary and secondary alcohols into carbonyl compounds. The reaction can mean loss of electrons, loss of hydrogen, or addition of oxygen. Oxidation is the opposite of reduction, so carbonyls can be reduced to alcohols, and alcohols can be oxidized back to carbonyls.

The product depends on the alcohol type and the hydrogens on the alpha-carbon, the carbon next to the hydroxyl group. Primary alcohols can become aldehydes and then carboxylic acids. Secondary alcohols can be oxidized only to ketones. Tertiary alcohols do not have alpha-protons, so they cannot be oxidized in this way.

Common oxidizing agents include the Jones reagent and potassium permanganate. Jones reagent is chromium trioxide in aqueous sulfuric acid with acetone. It forms a chromate ester intermediate and then follows an E2 pathway to give the carbonyl product. With a secondary alcohol, the reaction stops at a ketone. With a primary alcohol, the oxidation can continue to a carboxylic acid.

Potassium permanganate is also a strong oxidizing agent. It, too, converts primary alcohols to carboxylic acids. When an aldehyde is the goal, a more selective reagent such as pyridinium chlorochromate, or PCC, is used. Chromium-based reagents can be a concern because they use higher oxidation states of chromium, which are toxic.

Greener alternatives include Swern oxidation and Dess-Martin oxidation. These methods use reagents such as oxalyl chloride, dimethyl sulfoxide, triethylamine, and dichloromethane, which are relatively non-toxic. They convert primary alcohols into aldehydes and secondary alcohols into ketones. In the Swern reaction, the mechanism goes through an alkyl-sulfonium compound. In the Dess-Martin reaction, it goes through a periodinane intermediate.

Alcohol Oxidation Reagents and Products

structure and nomenclature of alcohols and phenols

structure-and-nomenclature-of-alcohols-and-phenols

Alcohols and Phenols: Naming Basics

Alcohols and phenols are important organic compounds with simple naming rules. Alcohols contain a hydroxyl group, or –OH group, directly bonded to carbon. Phenols also contain an OH group, but it is attached directly to a benzene ring. Alcohols are usually colorless. Phenol is a white crystalline compound with a characteristic hospital smell. These compounds are named using formal and standard systems. The most widely used system is the International Union of Pure and Applied Chemistry, or...

physical properties of alcohols and phenols

physical-properties-of-alcohols-and-phenols

Alcohols and Phenols: Boiling Point Trends

Alcohols and phenols are organic compounds whose physical properties depend on structure. In alcohols, a hydroxy group is attached to a saturated carbon. In phenols, the hydroxy group is attached to an aromatic ring. Their boiling points and water solubility are shaped by hydrogen bonding and dispersion forces. The oxygen-hydrogen dipole in the hydroxy group allows intermolecular hydrogen bonding. This gives alcohols a higher boiling point than aliphatic hydrocarbons with similar molecular...

acidity and basicity of alcohols and phenols

acidity-and-basicity-of-alcohols-and-phenols

Why Phenols Are More Acidic Than Alcohols

Alcohols are weak acids and weak bases because the O–H bond is polar and the oxygen atom has lone pairs. The partially positive hydrogen can be lost as a proton, and the oxygen can also accept a proton. When an alcohol is protonated, hydroxide changes into water, which is a much better leaving group. Alcohols vary a little in acidity. Methanol, with a pKa of 15.5, is slightly stronger as an acid than water, which has a pKa of 15.7. Ethanol, tert-butanol, and many other alcohols are weaker...

preparation of alcohols via addition reactions

preparation-of-alcohols-via-addition-reactions

Alcohol Synthesis from Alkenes

Alcohol synthesis from alkenes can follow three addition reactions: acid-catalyzed hydration, oxymercuration-demercuration, and hydroboration-oxidation. These methods all add across the double bond, but they give different alcohol products from the same alkene. In acid-catalyzed hydration, water adds to the double bond in an acidic atmosphere. The acid lets the hydrogen in water act as an electrophile and attack the alkene. A proton first adds to the double bond and forms a carbocation, which...

acid-catalyzed dehydration of alcohols to alkenes

acid-catalyzed-dehydration-of-alcohols-to-alkenes

Alcohol Dehydration Pathways to Alkene Products

Alcohol dehydration forms alkenes and water by removing a hydroxyl group and a hydrogen from a neighboring carbon. This reaction is usually done by heating the alcohol with an acid catalyst. Primary alcohols need higher temperatures and stronger acid conditions, while secondary and tertiary alcohols can react under milder conditions. Secondary and tertiary alcohols usually dehydrate through an E1 mechanism. In the first fast step, the alcohol is protonated and becomes an alkyloxonium ion. Then...

alcohols from carbonyl compounds: reduction

alcohols-from-carbonyl-compounds-reduction

Making Alcohols by Carbonyl Reduction

Making alcohols by carbonyl reduction is a key reaction in organic chemistry. It converts a carbonyl group into a hydroxyl group. The main routes are catalytic hydrogenation, hydride reduction, and borane reduction. Catalytic hydrogenation works by adding H2 across the pi bond of the carbonyl group. It uses transition metal catalysts such as Raney Ni, Pd-C, Pt, or Ru. Aldehydes and ketones can be reduced this way under mild to moderate heat, usually 25–100°C, and H2 pressure of about 1–5 atm.

alcohols from carbonyl compounds: grignard reaction

alcohols-from-carbonyl-compounds-grignard-reaction

Grignard Reagents in Alcohol Synthesis

Grignard reagents are key tools for making alcohols from carbonyl compounds. They are organomagnesium halides with a highly polar carbon–magnesium bond. Because this bond is partly ionic, the carbon acts as a strong nucleophile. It attacks the carbonyl carbon, which is the electrophilic part of a carbonyl group. Magnesium in the reagent also helps the reaction move forward. It coordinates with the carbonyl oxygen and lowers the electron density on the carbonyl carbon. This makes the carbonyl...

protection of alcohols

Alcohol Protecting Groups in Synthesis

Alcohol protecting groups help control which part of an organic molecule reacts during synthesis. A protecting group is a masking agent that makes a more reactive species inert under a chosen set of conditions. The lesson uses a pipe-flow analogy to show how this improves reaction selectivity. It also shows how protecting an alcohol can allow an organolithium alkylation of a halide to occur when the alcohol would otherwise compete. Common protecting groups for alcohols include trialkylsilyl...

preparation of diols and pinacol rearrangement

preparation-of-diols-and-pinacol-rearrangement

Pinacol Rearrangement of Vicinal Diols

Vicinal diols are compounds with two hydroxyl groups on adjacent carbon atoms. They are also called glycols. Under acidic conditions, these diols can undergo a pinacol rearrangement. The reaction starts when the acid catalyst transfers a proton to one hydroxyl group. This forms an oxonium ion. The oxonium ion then loses water and creates a tertiary carbocation intermediate. Next, a methyl group migrates from one carbon to the neighboring carbon. This step forms a resonance-stabilized cation...

conversion of alcohols to alkyl halides

Alcohols to Halides: Reagents and Mechanisms

Alcohols can be turned into alkyl halides by using reagents that make the hydroxyl group a better leaving group. The hydroxyl group is first protonated, which helps the reaction move forward. From there, the pathway can follow either an SN1 or SN2 substitution, depending on the starting alcohol and the reaction conditions. Tertiary alcohols usually form tertiary alkyl halides through a two-step SN1 mechanism. This route goes through a carbocation intermediate, and hyperconjugation helps...

Alcohol oxidation changes primary and secondary alcohols into carbonyl compounds. The reaction can mean loss of electrons, loss of hydrogen, or addition of oxygen. Oxidation is the opposite of reduction, so carbonyls can be reduced to alcohols, and alcohols can be oxidized back to carbonyls. The product depends on the alcohol type and the hydrogens on the alpha-carbon, the carbon next to the hydroxyl group. Primary alcohols can become aldehydes and then carboxylic acids. Secondary alcohols can...

preparation of alcohols via substitution reactions

preparation-of-alcohols-via-substitution-reactions

Alcohol Formation from Alkyl Halides

Alcohols can be made from alkyl halides by nucleophilic substitution. In these reactions, the carbon-halogen bond is highly polar, so the halide can leave the molecule. A nucleophile such as hydroxide ion or water then replaces the halide and forms an alcohol. The reaction path depends on the alkyl halide. Primary alkyl halides usually form primary alcohols through the SN2 mechanism. In SN2, the nucleophile attacks the halogen-bearing carbon from the side opposite the carbon-halogen bond. With...

key terms and concepts

Learn how primary, secondary, and tertiary alcohols oxidize, and compare Jones reagent, KMnO4, PCC, Swern oxidation, and Dess-Martin oxidation.

Alcohol Oxidation Reagents and Products | JoVE K12

organic chemistry

JoVE Core Organic Chemistry explains basic concepts of stereochemistry, reactions, and mechanisms using concise and easy-to-understand animated video lessons. Additionally, the scientist-in-action videos demonstrate the application of related concepts in classical and original research experiments performed in today's laboratories worldwide.

Alcohol Oxidation Reagents and Products

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