Alcohol Reactions: Oxidation Reactions - Online Tutor, Practice Problems & Exam Prep

Alcohol reactions, particularly oxidation reactions, are crucial in organic chemistry, where the goal is to increase the number of carbon-oxygen bonds without breaking carbon-carbon bonds. Oxidizing agents like sodium dichromate or potassium dichromate, dissolved in sulfuric acid, facilitate the transformation of alcohols into carbonyl compounds, such as aldehydes or ketones. These compounds can undergo further oxidation to form carboxylic acids. Understanding these reactions is essential for manipulating functional groups in alcohols and achieving desired oxidation products in synthetic chemistry.

Alcohol Reactions: Oxidation Reactions

In this video, we're going to take a look at alcohol reactions in terms of oxidation reactions. So we're going to say here that the oxidizing agent of either sodium dichromate or potassium dichromate their interchangeably cause sodium and potassium are both group 1A elements. It's really the dichromate portion that's the oxidizing agent. So here we have the oxidizing agent of either one of these, dissolved in sulfuric acid reacts with an alcohol, now an oxidizing agent.

This is the compound used to oxidize alcohols, and here we're going to say it adds as many carbon oxygen bonds as possible without breaking any carbon carbon bonds. Now if we take a look here, we're graying out our hydrocarbon and we're graying out our carbon dioxide. We're focused mainly on the shaded portion. This is the portion in organic chemistry where we deal with oxidation reactions.

So here we have an alcohol and this alcohol. Here we could oxidize it to a carbonyl compound. Here in this example we see it as an aldehyde, but it could also represent a ketone. OK, so here this middle section could represent an aldehyde or a ketone. Then that could also further oxidize to give us a carboxylic acid.

So we're talking about oxidation. We're really focusing on these types of functional groups. Alcohols to aldehydes or ketones to carboxylic acid if necessary. Now just remember, we're trying to add as many carbon oxygen bonds without breaking any carbon carbon bonds. This is the rule that we have to follow to get our proper oxidized product.

Alcohol Reactions Oxidation Reactions Example

Here it says determine the product created under the following oxidation reaction. So here we have our alcohol. We have potassium dichromate as our oxidizing agent over sulfuric acid. So remember we want to add as many carbon oxygen bonds without breaking any carbon carbon bonds.

So if we take a look here, we have chapter three, chapter 2, Chapter 2, and here it's going to be important that I show the bonds that could potentially be affected for this alcohol. Now we know that if we're oxidizing this, we know that we're going to form at least a carbon double bonded to an oxygen. And if I do that, this carbons already making three bonds. Remember it can only go up to four bonds here.

If I just had it as an H here, we'd have an aldehyde. But have I gone the full distance to replace any carbon hydrogen bonds with as many carbon oxygen bonds? I haven't because I could remove this H and put an oxygen there. So I've made as many carbon oxygen bonds as possible. And remember I cannot break a carbon carbon bond so this bond here is unaffected.

So at the end I would get a carbacillic acid as my final product.

Determine the product created under the following oxidation reaction.

• A.
• B.
• C.
• D. $CH_3CH_2CH_2CH_2CH_3$

Which of the following alcohols cannot undergo an oxidation reaction?

• A. $2-butanol$
• B. $3-heptanol$
• C. $2-methyl-2-propanol$
• D. $1-propanol$

Here’s what students ask on this topic:

What type of compound(s) does the oxidation of a primary alcohol produce?

The oxidation of a primary alcohol can produce two different types of compounds, depending on the extent of the oxidation and the conditions under which the reaction occurs.

1. Aldehyde: When a primary alcohol undergoes a mild oxidation, it is converted into an aldehyde. This reaction typically requires a mild oxidizing agent and may be performed under controlled conditions to prevent further oxidation.
2. Carboxylic Acid: If the oxidation of the primary alcohol continues beyond the aldehyde stage, or if stronger oxidizing agents are used, the aldehyde can be further oxidized to form a carboxylic acid. This is a more extensive oxidation process.

In summary, primary alcohols can be oxidized to form either aldehydes or carboxylic acids, with the specific product depending on the reaction conditions and the strength of the oxidizing agent.

What classification of alcohol undergoes oxidation to yield a ketone?

Secondary alcohols are the class of alcohols that undergo oxidation to yield ketones. In organic chemistry, alcohols are classified based on the number of carbon atoms attached to the carbon bearing the hydroxyl (-OH) group. A primary alcohol has the hydroxyl group connected to a carbon atom that is attached to only one other carbon. A secondary alcohol has the hydroxyl group on a carbon atom that is connected to two other carbons. Finally, a tertiary alcohol has the hydroxyl group on a carbon atom bonded to three other carbon atoms.

When a secondary alcohol undergoes an oxidation reaction, typically using an oxidizing agent like potassium dichromate (K₂Cr₂O₇) in an acidic medium or other suitable oxidants, the hydrogen atom from the hydroxyl group and a hydrogen atom from the adjacent carbon atom are removed. This process forms a double bond with oxygen, resulting in the creation of a ketone. The general formula for this oxidation can be represented as:

$R_1-\mathrm{CHOH}-R_2\to R_1-\mathrm{CO}-R_2$

where R₁ and R₂ are alkyl or aryl groups.

What type of alcohol is resistant to oxidation?

Alcohols that are resistant to oxidation generally have a structure that prevents the alcohol group from being easily converted to a carbonyl group (such as an aldehyde or ketone). Tertiary alcohols are resistant to oxidation because they have no hydrogen atom attached to the carbon with the -OH group. This structure makes it difficult for common oxidizing agents to remove the necessary hydrogen. In contrast, primary and secondary alcohols can be oxidized because they have hydrogen atoms on the carbon with the -OH group that can be removed. For example, tertiary butyl alcohol (t-butanol) is resistant to oxidation under standard conditions, as there are no hydrogen atoms on the tertiary carbon (the one bearing the -OH group) for an oxidizing agent to remove.

What is the product of the complete oxidation of a primary alcohol?

The complete oxidation of a primary alcohol typically results in the formation of a carboxylic acid. When a primary alcohol undergoes oxidation, the process usually occurs in two stages. In the first stage, the primary alcohol is oxidized to an aldehyde. This happens when the alcohol group (-OH) is converted to an aldehyde group (-CHO) by the removal of two hydrogen atoms.

If the oxidation continues (complete oxidation), the aldehyde is further oxidized to a carboxylic acid. This involves the addition of an oxygen atom to the aldehyde group, converting it into a carboxyl group (-COOH). The oxidizing agents commonly used for this process include potassium dichromate (K₂Cr₂O₇) in sulfuric acid (H₂SO₄) or potassium permanganate (KMnO₄) under acidic conditions. The reaction is typically carried out by heating the primary alcohol with the oxidizing agent, and the resulting carboxylic acid has the same number of carbon atoms as the original alcohol molecule.

Why is tertiary alcohol resistant to oxidation?

Tertiary alcohols are resistant to oxidation compared to primary and secondary alcohols because of their molecular structure. In a tertiary alcohol, the carbon atom that carries the hydroxyl (OH) group is attached to three other carbon atoms. This means there are no hydrogen atoms attached to the carbon with the hydroxyl group that can be removed during the oxidation process.

Oxidation reactions typically involve the removal of hydrogen atoms to form a carbonyl group (C=O). Since tertiary alcohols lack the necessary hydrogen atoms on the carbon with the hydroxyl group, they cannot easily form carbonyl compounds. Primary and secondary alcohols have one or two hydrogens, respectively, attached to the carbon with the OH group, which can be oxidized to form aldehydes, ketones, or carboxylic acids. Therefore, without these available hydrogens, tertiary alcohols are generally resistant to oxidation under standard conditions.