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Ch.6 - Alkyl Halides; Nucleophilic Substitution
Wade - Organic Chemistry 9th Edition
Wade9th EditionOrganic ChemistryISBN: 9780135213728Not the one you use?Change textbook
All textbooksWade 9th EditionCh.6 - Alkyl Halides; Nucleophilic SubstitutionProblem 40a,b
Chapter 6, Problem 40a,b

Give the substitution products expected from solvolysis of each compound by heating in ethanol.
(a)
(b)

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1
Step 1: Identify the type of reaction. Solvolysis in ethanol typically proceeds via an SN1 mechanism, especially for tertiary alkyl halides or secondary alkyl halides with good leaving groups. The leaving group departs first, forming a carbocation intermediate.
Step 2: Analyze compound (a). The bromine atom is attached to a tertiary carbon, which is highly favorable for carbocation formation. Upon heating in ethanol, the bromine leaves, forming a tertiary carbocation. Ethanol, acting as a nucleophile, will attack the carbocation to form the substitution product.
Step 3: Analyze compound (b). The chlorine atom is attached to a secondary carbon in a cyclohexane ring. The chlorine leaves, forming a secondary carbocation. Ethanol will then attack the carbocation to form the substitution product. Consider possible rearrangements if the carbocation can stabilize further.
Step 4: Consider stereochemistry. For both compounds, the products may exhibit stereochemical outcomes depending on the attack of ethanol on the planar carbocation intermediate. This can lead to racemic mixtures if the carbocation is chiral.
Step 5: Summarize the substitution products. For compound (a), the product will be an ethyl ether derivative of the tertiary carbon. For compound (b), the product will be an ethyl ether derivative of the secondary carbon in the cyclohexane ring.

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Key Concepts

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

Solvolysis

Solvolysis is a type of nucleophilic substitution reaction where a solvent acts as the nucleophile. In organic chemistry, this often involves the reaction of alkyl halides with polar protic solvents like ethanol. The solvent can replace the leaving group (e.g., bromide) in the substrate, leading to the formation of substitution products.
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Understanding the properties of SN1.

Nucleophilic Substitution Mechanisms

Nucleophilic substitution can occur via two primary mechanisms: SN1 and SN2. The SN1 mechanism involves a two-step process where the leaving group departs first, forming a carbocation intermediate, followed by nucleophilic attack. In contrast, the SN2 mechanism is a one-step process where the nucleophile attacks the substrate simultaneously as the leaving group departs, leading to a concerted reaction.
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Carbocation Stability

The stability of carbocations is crucial in determining the pathway of solvolysis reactions. Tertiary carbocations are more stable than secondary or primary ones due to hyperconjugation and inductive effects from surrounding alkyl groups. This stability influences whether the reaction will proceed via the SN1 or SN2 mechanism, affecting the substitution products formed.
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Related Practice
Textbook Question

Chlorocyclohexane reacts with sodium cyanide (NaCN) in ethanol to give cyanocyclohexane. The rate of formation of cyanocyclohexane increases when a small amount of sodium iodide is added to the solution. Explain this acceleration in the rate.

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Textbook Question

When tert-butyl bromide is heated with an equal amount of ethanol in an inert solvent, one of the products is ethyl tert-butyl ether.

a. What happens to the reaction rate if the concentration of ethanol is doubled?

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Textbook Question

Allylic halides have the structure

a. Show how the first-order ionization of an allylic halide leads to a resonance-stabilized cation.

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Textbook Question

Give the substitution products expected from solvolysis of each compound by heating in ethanol.

(c)

(d)

Textbook Question

When tert-butyl bromide is heated with an equal amount of ethanol in an inert solvent, one of the products is ethyl tert-butyl ether.

b. What happens to the rate if the concentration of tert-butyl bromide is tripled and the concentration of ethanol is doubled?

c. What happens to the rate if the temperature is raised?

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Textbook Question

Allylic halides have the structure

b. Draw the resonance structures of the allylic cations formed by ionization of the following halides.

(i)

(ii)

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