Ch. 14 - Ethers, Epoxides, and Thioethers

Wade9th EditionOrganic ChemistryISBN: 9780135213728Not the one you use?Change textbook

Wade 9th Edition

Ch. 14 - Ethers, Epoxides, and Thioethers

Problem 46

Chapter 14, Problem 46

Show how you would convert 3-bromocyclohexanol to the following diol. You may use any additional reagents you need.

Verified step by step guidance

Step 1: Begin by replacing the bromine atom in 3-bromocyclohexanol with a nucleophile to form a cyclohexanol derivative. This can be achieved using a substitution reaction, such as an SN2 reaction, with a suitable nucleophile like cyanide (CN⁻) to introduce a functional group that can be further modified.

Step 2: Perform a hydrolysis reaction on the nitrile group (if introduced in Step 1) to convert it into a carboxylic acid. This can be done using acidic or basic hydrolysis conditions.

Step 3: Reduce the carboxylic acid group to a primary alcohol using a reducing agent such as lithium aluminum hydride (LiAlH₄). This will yield a cyclohexanol derivative with an additional alcohol group.

Step 4: Introduce branching at the carbon adjacent to the hydroxyl group by performing an alkylation reaction. This can be achieved by converting the alcohol into a leaving group (e.g., tosylate) and then reacting it with an alkyl halide under basic conditions.

Step 5: Adjust the stereochemistry of the product, if necessary, by using selective reagents or conditions to ensure the desired diol configuration is achieved. This may involve epimerization or other stereoselective transformations.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Nucleophilic Substitution

Nucleophilic substitution is a fundamental reaction in organic chemistry where a nucleophile attacks an electrophilic carbon atom, replacing a leaving group. In this case, the bromine atom in 3-bromocyclohexanol acts as a leaving group, allowing for the introduction of new functional groups through subsequent reactions. Understanding this mechanism is crucial for converting the starting material into the desired diol.

Reduction Reactions

Reduction reactions involve the gain of electrons or hydrogen, often resulting in the conversion of carbonyl groups to alcohols. In the context of this transformation, a reduction step may be necessary to convert an intermediate compound into the final diol product. Recognizing the appropriate reducing agents, such as lithium aluminum hydride or sodium borohydride, is essential for successful synthesis.

Stereochemistry

Stereochemistry refers to the spatial arrangement of atoms in molecules and how this affects their chemical behavior. The conversion of 3-bromocyclohexanol to the target diol involves careful consideration of stereochemical outcomes, particularly if chiral centers are formed or altered. Understanding stereochemical principles is vital for predicting the configuration of the final product and ensuring the correct diol is synthesized.

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Related Practice

Textbook Question

Propylene oxide is a chiral molecule. Hydrolysis of propylene oxide gives propylene glycol, another chiral molecule.

(a) Draw the enantiomers of propylene oxide.

(b) Propose a mechanism for the acid-catalyzed hydrolysis of pure (R)-propylene oxide.

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Textbook Question

Show how you would synthesize the following ethers in good yield from the indicated starting materials and any additional reagents needed.

(d) 1-methoxydecane from a decene

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Textbook Question

There are two different ways of making 2-ethoxyoctane from octan-2-ol using the Williamson ether synthesis. When pure (–)-octan-2-ol of specific rotation -8.24° is treated with sodium metal and then ethyl iodide, the product is 2-ethoxyoctane with a specific rotation of -15.6°. When pure (–)-octan-2-ol is treated with tosyl chloride and pyridine and then with sodium ethoxide, the product is also 2-ethoxyoctane. Predict the rotation of the 2-ethoxyoctane made using the tosylation/sodium ethoxide procedure, and propose a detailed mechanism to support your prediction.

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Textbook Question

An acid-catalyzed reaction was carried out using methyl cellosolve (2-methoxyethanol) as the solvent. When the 2-methoxyethanol was redistilled, a higher-boiling fraction (bp 162°C) was also recovered. The mass spectrum of this fraction showed the molecular weight to be 134. The IR and NMR spectra are shown here. Determine the structure of this compound, and propose a mechanism for its formation.

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Textbook Question

Show how you would synthesize the following ethers in good yield from the indicated starting materials and any additional reagents needed.

(f) trans-2,3-epoxyoctane from octan-2-ol

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Textbook Question

Show how you would synthesize the following ethers in good yield from the indicated starting materials and any additional reagents needed.

(e) 1-ethoxy-1-methylcyclohexane from 2-methylcyclohexanol

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