Skip to main content
Ch.11 - Reactions of Alcohols
Wade - Organic Chemistry 9th Edition
Wade9th EditionOrganic ChemistryISBN: 9780135213728Not the one you use?Change textbook
All textbooksWade 9th EditionCh.11 - Reactions of AlcoholsProblem 19
Chapter 11, Problem 19

Suggest how you would convert trans-4-methylcyclohexanol to
a. trans-1-chloro-4-methylcyclohexane.
b. cis-1-chloro-4-methylcyclohexane.

Verified step by step guidance
1
Step 1: Recognize that the starting compound, trans-4-methylcyclohexanol, is a secondary alcohol. To convert it into a chlorinated compound, the hydroxyl group (-OH) must first be replaced with a chlorine atom (-Cl). This can be achieved using reagents like thionyl chloride (SOCl₂) or phosphorus trichloride (PCl₃).
Step 2: For part (a), to obtain trans-1-chloro-4-methylcyclohexane, ensure that the stereochemistry of the product remains trans. The reaction with SOCl₂ typically proceeds via an SN2 mechanism, which inverts the configuration at the carbon bearing the hydroxyl group. Since the starting material is trans, the inversion will maintain the trans relationship between the substituents. Use SOCl₂ in the presence of pyridine to achieve this.
Step 3: For part (b), to obtain cis-1-chloro-4-methylcyclohexane, the stereochemistry must be altered. This can be achieved by first converting the alcohol into a good leaving group, such as a tosylate (using p-toluenesulfonyl chloride and pyridine), followed by an SN2 substitution with an appropriate nucleophile like Cl⁻. The SN2 mechanism will invert the configuration at the carbon, resulting in the cis product.
Step 4: Ensure that the reaction conditions are carefully controlled to favor the desired stereochemical outcome. For part (a), the direct use of SOCl₂ is sufficient. For part (b), the tosylation step followed by substitution is necessary to achieve the inversion required for the cis product.
Step 5: Verify the stereochemistry of the final products using spectroscopic techniques such as NMR or by analyzing the product's physical properties. This ensures that the desired trans or cis isomer has been successfully synthesized.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
6m
Was this helpful?

Key Concepts

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

Stereochemistry

Stereochemistry is the study of the spatial arrangement of atoms in molecules and how this affects their chemical behavior. In this question, understanding the difference between trans and cis isomers is crucial, as it influences the reactivity and the products formed during chemical reactions. The stereochemical configuration of the starting material and the desired products must be carefully considered to achieve the correct transformation.
Recommended video:
1:38
Polymer Stereochemistry Concept 1

Nucleophilic Substitution Reactions

Nucleophilic substitution reactions involve the replacement of a leaving group in a molecule with a nucleophile. In the context of converting alcohols to alkyl halides, this typically involves the conversion of the alcohol (trans-4-methylcyclohexanol) to a better leaving group, such as a chloride, through reactions like the conversion to a tosylate followed by nucleophilic attack. Understanding the mechanism (SN1 or SN2) is essential for predicting the stereochemical outcome.
Recommended video:
Guided course
01:47
Nucleophiles and Electrophiles can react in Substitution Reactions.

Rearrangement and Elimination Reactions

Rearrangement and elimination reactions can alter the structure of a molecule, affecting its stereochemistry. In this case, to achieve the cis product, one might need to consider elimination reactions that lead to the formation of a double bond, followed by a stereospecific addition of a halogen. Recognizing how these reactions can be manipulated to achieve the desired stereochemical configuration is key to solving the problem.
Recommended video:
Guided course
06:28
Definition of Cope Rearrangement
Related Practice
Textbook Question

Predict the products of the sulfuric acid-catalyzed dehydration of the following alcohols. When more than one product is expected, label the major and minor products.

(d) 1-isopropylcyclohexanol

(e) 2-methylcyclohexanol

2
views
Textbook Question

Write balanced equations for the three preceding reactions.

2
views
Textbook Question

Two products are observed in the following reaction.

a. Suggest a mechanism to explain how these two products are formed.

b. Your mechanism for part (a) should be different from the usual mechanism of the reaction of SOCl2 with alcohols. Explain why the reaction follows a different mechanism in this case.

3
views
Textbook Question

Give the structures of the products you would expect when each alcohol reacts with (1) HCl, ZnCl2; (2) HBr; (3) PBr3; (4) P/I2; and (5) SOCl2.

(a) butan-1-ol

(b) 2-methylbutan-2-ol

1
views
Textbook Question

When cis-2-methylcyclohexanol reacts with the Lucas reagent, the major product is 1-chloro-1-methylcyclohexane. Propose a mechanism to explain the formation of this product.

9
views
Textbook Question

Explain the products observed in the following reaction of an alcohol with the Lucas reagent.