What Compound Is Produced When 3-pentanol Is Subjected To Controlled Oxidation?

2.5 Reactions of Alcohols

Learning Objectives

1. Give two major types of reactions of alcohols.
2. Depict the result of the oxidation of a primary alcohol.
3. Draw the result of the oxidation of a secondary alcohol.

Chemical reactions in alcohols occur mainly at the functional group, but some involve hydrogen atoms fastened to the OH-begetting carbon cantlet or to an adjacent carbon cantlet. Of the three major kinds of alcohol reactions, which are summarized in Figure 2.4 "Reactions of Alcohols", two—dehydration and oxidation—are considered here. The third reaction type—esterification—is covered in Chapter 4 "Carboxylic Acids, Esters", Department 4.8 "Preparation of Esters".

Effigy two.iv Reactions of Alcohols

Oxidation and dehydration of alcohols are considered here.

Dehydration

Every bit noted in Figure ii.four "Reactions of Alcohols", an alcohol undergoes aridity in the presence of a goad to form an alkene and water. The reaction removes the OH group from the alcohol carbon atom and a hydrogen cantlet from an next carbon atom in the aforementioned molecule:

Under the proper weather condition, it is possible for the dehydration to occur betwixt 2 alcohol molecules. The entire OH group of one molecule and only the hydrogen atom of the OH group of the second molecule are removed. The ii ethyl groups attached to an oxygen atom form an ether molecule.

(Ethers are discussed in Department 2.4 "Reactions That Grade Alcohols".) Thus, depending on atmospheric condition, one can prepare either alkenes or ethers by the aridity of alcohols.

Notation

Both dehydration and hydration reactions occur continuously in cellular metabolism, with enzymes serving as catalysts and at a temperature of most 37°C. (For more data virtually hydration reactions, meet Chapter one "Organic Chemistry Review / Hydrocarbons", Section 1.14 "Chemical Properties of Alkenes".) The following reaction occurs in the Embden–Meyerhof pathway. (For more than information about metabolic reactions, see Chapter eleven "Metabolic Pathways and Energy Production".)

Although the participating compounds are complex, the reaction is the same: elimination of water from the starting material. The idea is that if you know the chemical science of a item functional group, yous know the chemical science of hundreds of different compounds.

Oxidation

Chief and secondary alcohols are readily oxidized. We saw earlier how methanol and ethanol are oxidized past liver enzymes to course aldehydes. Because a variety of oxidizing agents tin can bring nigh oxidation, we can indicate an oxidizing amanuensis without specifying a item one by writing an equation with the symbol [O] to a higher place the arrow. For case, nosotros write the oxidation of ethanol—a primary alcohol—to form acetaldehyde—an aldehyde—as follows:

We shall see (in Affiliate three "Aldehydes, Ketones" Department iii.1 "Aldehydes and Ketones: Structure and Names") that aldehydes are even more than easily oxidized than alcohols and yield carboxylic acids.

Secondary alcohols are oxidized to ketones. The oxidation of isopropyl booze by potassium dichromate (K₂Cr_twoO₇) gives acetone, the simplest ketone:

Dissimilar aldehydes, ketones are relatively resistant to further oxidation (Chapter 3 "Aldehydes, Ketones" Section 3.ane "Aldehydes and Ketones: Structure and Names"), so no special precautions are required to isolate them as they form.

Annotation that in oxidation of both primary (RCH₂OH) and secondary (R_twoCHOH) alcohols, two hydrogen atoms are removed from the alcohol molecule, one from the OH grouping and other from the carbon atom that bears the OH group.

Note

These reactions tin can also exist carried out in the laboratory with chemical oxidizing agents. One such oxidizing amanuensis is potassium dichromate. The balanced equation (showing only the species involved in the reaction) in this instance is as follows:

Alcohol oxidation is of import in living organisms. Enzyme-controlled oxidation reactions provide the energy cells need to do useful work. 1 stride in the metabolism of carbohydrates involves the oxidation of the secondary alcohol group in isocitric acid to a ketone group:

Note that the overall type of reaction is the same as that in the conversion of isopropyl booze to acetone. (For more data on metabolic reactions, see Chapter eleven "Metabolic Pathways and Energy Production".)

Tertiary alcohols (R₃COH) are resistant to oxidation because the carbon atom that carries the OH group does not have a hydrogen atom attached merely is instead bonded to other carbon atoms. The oxidation reactions we have described involve the germination of a carbon-to-oxygen double bond. Thus, the carbon atom bearing the OH grouping must be able to release one of its attached atoms to course the double bond. The carbon-to-hydrogen bonding is hands broken under oxidative weather condition, only carbon-to-carbon bonds are not. Therefore tertiary alcohols are not easily oxidized.

Example 4

Write an equation for the oxidation of each booze. Use [O] in a higher place the pointer to indicate an oxidizing agent. If no reaction occurs, write "no reaction" later on the arrow.

1. CH₃CH₂CH₂CH_twoCH₂OH

2. 

3. 

Solution

The first step is to recognize the class of each alcohol as main, secondary, or tertiary.

1. This booze has the OH group on a carbon cantlet that is attached to only 1 other carbon cantlet, and then information technology is a chief alcohol. Oxidation forms first an aldehyde and farther oxidation forms a carboxylic acid.

   

2. This booze has the OH group on a carbon cantlet that is attached to three other carbon atoms, so it is a tertiary alcohol. No reaction occurs.

   

3. This booze has the OH group on a carbon cantlet that is attached to 2 other carbon atoms, and then information technology is a secondary alcohol; oxidation gives a ketone.

   

Skill-Edifice Exercise

Write an equation for the oxidation of each booze. Use [O] above the arrow to indicate an oxidizing amanuensis. If no reaction occurs, write "no reaction" after the arrow.

1. 

2. 

3. 

Concept Review Exercises

1. In a reaction, compound W with the molecular formula C₄H₁₀O is converted to compound X with the formula C₄H₈O. Is W oxidized, reduced, dehydrated, or none of these? Explain.

2. In a reaction, 2 mol of chemical compound Y with the molecular formula C₄H₁₀O is converted to 1 mol of chemical compound Z with the formula C₈H_xviiiO. Is Y oxidized, reduced, or neither? Explain.

Answers

1. oxidized; H is removed

2. neither; water is removed

Fundamental Takeaways

• Alcohols tin can be dehydrated to course either alkenes (higher temperature, excess acid) or ethers (lower temperature, backlog alcohol).
• Primary alcohols are oxidized to form aldehydes.
• Secondary alcohols are oxidized to form ketones.
• 3rd alcohols are not readily oxidized.

Exercises

i. Name the three major types of chemical reactions of alcohols.

two. Why do tertiary alcohols non undergo oxidation? Tin can a tertiary alcohol undergo aridity?

3. Draw the structure of the production for each reaction.

a.

b.

4. Draw the construction of the product for each reaction.

a.

b.\

5. Write an equation for the dehydration of 2-propanol to yield each compound blazon.

a. an alkene

b. an ether

half-dozen. Describe the structure of the alkene formed by the dehydration of cyclohexanol.

Answers

1. aridity, oxidation, and esterification

3.

a.

b.

5.

a.

b.

What Compound Is Produced When 3-pentanol Is Subjected To Controlled Oxidation?,

Source: https://guides.hostos.cuny.edu/che120/chapter2

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