Related Experiment Video
Updated: Jul 9, 2026
08:12
A Two-Step Protocol for Umpolung Functionalization of Ketones Via Enolonium Species
Published on: August 16, 2018
Efficiency of bulky protic solvent for SN2 reaction
Sung-Sik Lee1, Ho-Sung Kim, Tae-Kyu Hwang
1College of Environmental Science and Applied Chemistry (BK 21), Kyunghee University, Kyungki 446-701, S. Korea.
Organic Letters
|December 7, 2007
Summary
Aprotic solvents like acetonitrile accelerate SN2 reactions more than small protic solvents. Bulky protic solvents, such as tert-butyl alcohol, also enhance SN2 reaction rates, matching acetonitrile efficiency.
Area of Science:
- Physical Chemistry
- Organic Chemistry
Background:
- Solvent effects significantly influence reaction kinetics.
- Understanding solvent polarity and hydrogen bonding is crucial for predicting reaction rates.
Purpose of the Study:
- To computationally investigate and compare the impact of aprotic and protic solvents on the rate of a specific SN2 reaction.
- To determine the relative efficiency of acetonitrile, methanol, and tert-butyl alcohol as solvents for the SN2 reaction.
Main Methods:
- Computational chemistry methods were employed to calculate activation barriers.
- The SN2 reaction F- + C3H7OMs --> C3H7F + OMs- was modeled in different solvent environments.
Main Results:
- Acetonitrile (aprotic) demonstrated higher efficiency in accelerating the SN2 reaction compared to methanol (small protic solvent).
- Tert-butyl alcohol (bulky protic solvent) was predicted to be highly efficient, with a rate constant comparable to acetonitrile.
- Calculated activation barriers correlated well with experimental observations across the studied solvents.
Conclusions:
- Solvent choice critically impacts SN2 reaction rates, with aprotic solvents and sterically hindered protic solvents showing enhanced efficiency.
- Computational modeling provides accurate predictions of solvent effects on SN2 reaction kinetics.
- Findings offer valuable insights for optimizing reaction conditions in organic synthesis.
More Related Videos
Related Concept Videos
02:27Predicting Products: SN1 vs. SN2
Nucleophilic substitution reactions of alkyl halides can proceed via an SN1 or an SN2 mechanism. While in SN2 reactions, the nucleophile attacks the substrate simultaneously as the leaving group departs, in SN1 reactions, the substrate first dissociates to give the carbocation intermediate. Various factors such as the structure of the substrate, the strength of the nucleophile, and the nature of the solvent promote one mechanism over the other.
With increased substitution on the alkyl halide,...
With increased substitution on the alkyl halide,...
02:25SN1 Reaction: Mechanism
Kinetic studies of ionization of a tertiary halide in a protic solvent suggest that only the substrate participates in the rate-determining step (slow step). The nucleophile is involved only after the slowest step. The SN1 reaction takes place in a multiple-step mechanism.
Firstly, the haloalkane ionizes to generate a carbocation intermediate and a halide ion. This heterolytic cleavage is highly endothermic with large activation energy. The ionization of the substrate, facilitated by a polar...
Firstly, the haloalkane ionizes to generate a carbocation intermediate and a halide ion. This heterolytic cleavage is highly endothermic with large activation energy. The ionization of the substrate, facilitated by a polar...
02:26SN2 Reaction: Transition State
An SN2 reaction of an alkyl halide is a single-step process in which bond formation between the nucleophile and the substrate and bond breaking between the substrate and the halide occurs simultaneously through a transition state without forming an intermediate.
When the nucleophile approaches the electrophilic carbon with its lone pairs, the halide acts as a leaving group and moves away with the electron-pair bonded to the carbon. Dotted partial bonds represent the bonds being formed or broken...
When the nucleophile approaches the electrophilic carbon with its lone pairs, the halide acts as a leaving group and moves away with the electron-pair bonded to the carbon. Dotted partial bonds represent the bonds being formed or broken...
02:27SN2 Reaction: Mechanism
The kinetic studies of SN2 reactions suggest an essential feature of its mechanism: it is a single-step process without intermediates. Here, both the nucleophile and the substrate participate in the rate-determining step.
The presence of the more electronegative halogen in the substrate creates a polarized carbon-halide bond. The halide pulls the electron cloud generating an electrophilic center at the carbon atom. Thus, the carbon atom carries a partial positive charge while the halide has a...
The presence of the more electronegative halogen in the substrate creates a polarized carbon-halide bond. The halide pulls the electron cloud generating an electrophilic center at the carbon atom. Thus, the carbon atom carries a partial positive charge while the halide has a...
02:15SN1 Reaction: Stereochemistry
This lesson provides an in-depth discussion of the stereochemical outcomes in an SN1 reaction.
In the first step of an SN1 reaction, the bond between the electrophilic carbon and the leaving group ionizes to generate the carbocation intermediate. The second step of the mechanism is the nucleophilic attack.
In the formed carbocation, the positively charged carbon is sp2 hybridized with a trigonal planar geometry. As all the three substituents lie on the same plane, a plane of symmetry for the...
In the first step of an SN1 reaction, the bond between the electrophilic carbon and the leaving group ionizes to generate the carbocation intermediate. The second step of the mechanism is the nucleophilic attack.
In the formed carbocation, the positively charged carbon is sp2 hybridized with a trigonal planar geometry. As all the three substituents lie on the same plane, a plane of symmetry for the...
02:14SN2 Reaction: Kinetics
Kinetic Studies and Significance
In a chemical reaction, a relationship exists between the concentration of reactants and the rate at which the reaction proceeds. The study to measure this relationship is known as the kinetics of a chemical reaction. Kinetic studies are used to deduce the rate law of a chemical reaction, which provides information about the species involved during the transition state of the rate-determining step. Thus, kinetic studies help to derive the mechanism of a reaction.
In a chemical reaction, a relationship exists between the concentration of reactants and the rate at which the reaction proceeds. The study to measure this relationship is known as the kinetics of a chemical reaction. Kinetic studies are used to deduce the rate law of a chemical reaction, which provides information about the species involved during the transition state of the rate-determining step. Thus, kinetic studies help to derive the mechanism of a reaction.