Skip to main content
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 33c,d
Chapter 6, Problem 33c,d

Predict the compound in each pair that will undergo the SN2 reaction faster.
(c) Two chemical structures with a chlorine atom, labeled "or," illustrating a comparison for SN2 reaction rates.
(d) Two chemical structures with bromine atoms, labeled "or," illustrating a comparison for SN2 reaction rates.

Verified step by step guidance
1
Step 1: Understand the SN2 reaction mechanism. SN2 reactions are bimolecular nucleophilic substitution reactions where the rate depends on both the nucleophile and the substrate. The reaction occurs in a single step with a backside attack, leading to inversion of configuration.
Step 2: Analyze the steric hindrance of the substrates. In SN2 reactions, steric hindrance around the electrophilic carbon (the carbon attached to the leaving group) significantly affects the reaction rate. Less sterically hindered substrates react faster.
Step 3: Compare the two compounds in pair (c). The compound on the left has a secondary carbon attached to the chlorine atom, while the compound on the right has a tertiary carbon attached to the chlorine atom. Tertiary carbons are more sterically hindered than secondary carbons, making the left compound more favorable for SN2 reactions.
Step 4: Compare the two compounds in pair (d). The compound on the left has a secondary carbon attached to the bromine atom, while the compound on the right has a tertiary carbon attached to the bromine atom. Similar to pair (c), the tertiary carbon in the right compound is more sterically hindered, making the left compound more favorable for SN2 reactions.
Step 5: Conclude that in both pairs (c) and (d), the compounds with secondary carbons attached to the leaving group (chlorine or bromine) will undergo the SN2 reaction faster due to reduced steric hindrance.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
5m
Was this helpful?

Key Concepts

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

SN2 Reaction Mechanism

The SN2 (substitution nucleophilic bimolecular) reaction is a type of nucleophilic substitution where the nucleophile attacks the electrophile simultaneously as the leaving group departs. This concerted mechanism results in a single transition state and is characterized by a second-order reaction rate, dependent on the concentration of both the nucleophile and the substrate.
Recommended video:
Guided course
08:33
Drawing the SN2 Mechanism

Steric Hindrance

Steric hindrance refers to the prevention of chemical reactions due to the spatial arrangement of atoms within a molecule. In SN2 reactions, increased steric hindrance around the electrophilic carbon can slow down the reaction rate, as bulky groups make it more difficult for the nucleophile to approach and attack the carbon center.
Recommended video:
Guided course
02:53
Understanding steric effects.

Leaving Group Ability

The ability of a leaving group to depart from a molecule is crucial in determining the rate of an SN2 reaction. A good leaving group, such as bromide (Br-) or iodide (I-), stabilizes the transition state and facilitates the reaction, while a poor leaving group, like chloride (Cl-), can slow down the reaction due to its stronger bond with the carbon atom.
Recommended video:
Guided course
03:06
How to use the factors affecting acidity to predict leaving group ability.
Related Practice
Textbook Question

Predict the compound in each pair that will undergo the SN2 reaction faster.

(a)

(b)

2349
views
Textbook Question

Show how you would convert (in one or two steps) 1-phenylpropane to the three products shown below. In each case, explain what unwanted reactions might produce undesirable impurities in the product.

744
views
Textbook Question

Predict the compound in each pair that will undergo solvolysis (in aqueous ethanol) more rapidly.

(c)


(d)

855
views
Textbook Question

Predict the compound in each pair that will undergo solvolysis (in aqueous ethanol) more rapidly.

(a) (CH3CH2)2CH—Cl or (CH3)3C—Cl

(b)

2256
views
Textbook Question

Show how each compound might be synthesized by the SN2 displacement of an alkyl halide.

e. H2C=CH—CH2CN

f. H—C≡C—CH2CH2CH3

2346
views
Textbook Question

Draw the structures of the following compounds.

a. sec-butyl chloride

b. isobutyl bromide

864
views