Reactions of N-Chlorobenzylalkylamines with Sodium Methoxide in Methanol. Steric Effects in Elimination Reactions

Bong Rae Cho; Jun Ho Maeng; Jong Chan Yoon; Tae Rin Kim

doi:10.1021/jo00230a018

Reactions of N-Chlorobenzylalkylamines with Sodium Methoxide in Methanol. Steric Effects in Elimination Reactions

Bong Rae Cho, Jun Ho Maeng, Jong Chan Yoon, Tae Rin Kim

* Honorary professors

Research output: Contribution to journal › Article › peer-review

10 Citations (Scopus)

Abstract

Reactions of N-chlorobenzylalkylamines in which the alkyl group is Me, Et, i-Pr, t-Bu, and sec-Bu with MeONa-MeOH have been investigated kinetically. The eliminations are quantitative and regiospecific, producing only benzylidenealkylamines. The reactions are first order in base and first order in substrate, and an E2 mechanism is evident. The relative rates of elimination at 25 °C are 1/0.5/0.3/0.2/0.01 for Me/Et/i-Pr/sec-Bu/t-Bu alkyl substituents, respectively. The results are attributed to repulsive interaction between the alkyl group and the base in the transition state. Hammett ρ and k_H/k_Dvalues decreased, but the ΔH*and ΔS* values increased with bulkier alkyl substituents. Changes in the transition-state parameters with the substrate steric effect are interpreted with variation in structure of the imine-forming transition states.

Original language	English
Pages (from-to)	4752-4756
Number of pages	5
Journal	Journal of Organic Chemistry
Volume	52
Issue number	21
DOIs	https://doi.org/10.1021/jo00230a018
Publication status	Published - 1987 Oct 1

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Organic Chemistry

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title = "Reactions of N-Chlorobenzylalkylamines with Sodium Methoxide in Methanol. Steric Effects in Elimination Reactions",

abstract = "Reactions of N-chlorobenzylalkylamines in which the alkyl group is Me, Et, i-Pr, t-Bu, and sec-Bu with MeONa-MeOH have been investigated kinetically. The eliminations are quantitative and regiospecific, producing only benzylidenealkylamines. The reactions are first order in base and first order in substrate, and an E2 mechanism is evident. The relative rates of elimination at 25 °C are 1/0.5/0.3/0.2/0.01 for Me/Et/i-Pr/sec-Bu/t-Bu alkyl substituents, respectively. The results are attributed to repulsive interaction between the alkyl group and the base in the transition state. Hammett ρ and kH/kDvalues decreased, but the ΔH*and ΔS* values increased with bulkier alkyl substituents. Changes in the transition-state parameters with the substrate steric effect are interpreted with variation in structure of the imine-forming transition states.",

author = "Cho, {Bong Rae} and Maeng, {Jun Ho} and Yoon, {Jong Chan} and Kim, {Tae Rin}",

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T1 - Reactions of N-Chlorobenzylalkylamines with Sodium Methoxide in Methanol. Steric Effects in Elimination Reactions

AU - Cho, Bong Rae

AU - Maeng, Jun Ho

AU - Yoon, Jong Chan

AU - Kim, Tae Rin

PY - 1987/10/1

Y1 - 1987/10/1

N2 - Reactions of N-chlorobenzylalkylamines in which the alkyl group is Me, Et, i-Pr, t-Bu, and sec-Bu with MeONa-MeOH have been investigated kinetically. The eliminations are quantitative and regiospecific, producing only benzylidenealkylamines. The reactions are first order in base and first order in substrate, and an E2 mechanism is evident. The relative rates of elimination at 25 °C are 1/0.5/0.3/0.2/0.01 for Me/Et/i-Pr/sec-Bu/t-Bu alkyl substituents, respectively. The results are attributed to repulsive interaction between the alkyl group and the base in the transition state. Hammett ρ and kH/kDvalues decreased, but the ΔH*and ΔS* values increased with bulkier alkyl substituents. Changes in the transition-state parameters with the substrate steric effect are interpreted with variation in structure of the imine-forming transition states.

AB - Reactions of N-chlorobenzylalkylamines in which the alkyl group is Me, Et, i-Pr, t-Bu, and sec-Bu with MeONa-MeOH have been investigated kinetically. The eliminations are quantitative and regiospecific, producing only benzylidenealkylamines. The reactions are first order in base and first order in substrate, and an E2 mechanism is evident. The relative rates of elimination at 25 °C are 1/0.5/0.3/0.2/0.01 for Me/Et/i-Pr/sec-Bu/t-Bu alkyl substituents, respectively. The results are attributed to repulsive interaction between the alkyl group and the base in the transition state. Hammett ρ and kH/kDvalues decreased, but the ΔH*and ΔS* values increased with bulkier alkyl substituents. Changes in the transition-state parameters with the substrate steric effect are interpreted with variation in structure of the imine-forming transition states.

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Reactions of N-Chlorobenzylalkylamines with Sodium Methoxide in Methanol. Steric Effects in Elimination Reactions

Abstract

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