Elimination Reactions of (E)- and (Z)-Benzaldehyde O-Benzoyloximes. Transition State Differences for the Syn- and Anti-Eliminations Forming Nitriles

Bong-Rae Cho, Hak Suk Chung, Nam Soon Cho

Research output: Contribution to journalArticle

30 Citations (Scopus)

Abstract

Elimination reactions of (E)- and (Z)-benzaldehyde O-benzoyloximes 1 and 2 with DBU in MeCN have been investigated kinetically. The reactions are second order and exhibit substantial values of Hammett ρ and kH/kD values, and an E2 mechanism is evident. The rate of elimination from 2 is approximately 36000 fold faster than that from 1. For reactions of 1 with DBU in MeCN, kH/kD = 3.3 ± 0.2, Hammett ρ value of 2.19 ± 0.05, β1g = -0.49 ± 0.02, ΔH‡ = 10.4 ± 0.6 kcal/mol, and ΔS‡ = -34.3 ± 2.6 eu have been determined. The corresponding values for 2 are kH/kD = 7.3 ± 0.2, ρ = 1.21 ± 0.05, β1g = -0.40 ± 0.01, ΔH‡ = 6.8 ± 0.5 kcal/mol, and ΔS‡ = -25.8 ± 1.9 eu, respectively. The results indicate that the anti-eliminations from 2 proceed via more symmetrical transition states with smaller degrees of proton transfer and Nα-OC (O)Ar bond cleavage, less negative charge development at the β-carbon, and a greater extent of triple bond formation than that for the syn-elimination.

Original languageEnglish
Pages (from-to)4685-4690
Number of pages6
JournalJournal of Organic Chemistry
Volume63
Issue number14
Publication statusPublished - 1998 Jul 10

Fingerprint

Nitriles
Proton transfer
Protons
Carbon
benzaldehyde

ASJC Scopus subject areas

  • Organic Chemistry

Cite this

Elimination Reactions of (E)- and (Z)-Benzaldehyde O-Benzoyloximes. Transition State Differences for the Syn- and Anti-Eliminations Forming Nitriles. / Cho, Bong-Rae; Chung, Hak Suk; Cho, Nam Soon.

In: Journal of Organic Chemistry, Vol. 63, No. 14, 10.07.1998, p. 4685-4690.

Research output: Contribution to journalArticle

@article{0ef1137b948b43ae84e948f34a9d5b79,
title = "Elimination Reactions of (E)- and (Z)-Benzaldehyde O-Benzoyloximes. Transition State Differences for the Syn- and Anti-Eliminations Forming Nitriles",
abstract = "Elimination reactions of (E)- and (Z)-benzaldehyde O-benzoyloximes 1 and 2 with DBU in MeCN have been investigated kinetically. The reactions are second order and exhibit substantial values of Hammett ρ and kH/kD values, and an E2 mechanism is evident. The rate of elimination from 2 is approximately 36000 fold faster than that from 1. For reactions of 1 with DBU in MeCN, kH/kD = 3.3 ± 0.2, Hammett ρ value of 2.19 ± 0.05, β1g = -0.49 ± 0.02, ΔH‡ = 10.4 ± 0.6 kcal/mol, and ΔS‡ = -34.3 ± 2.6 eu have been determined. The corresponding values for 2 are kH/kD = 7.3 ± 0.2, ρ = 1.21 ± 0.05, β1g = -0.40 ± 0.01, ΔH‡ = 6.8 ± 0.5 kcal/mol, and ΔS‡ = -25.8 ± 1.9 eu, respectively. The results indicate that the anti-eliminations from 2 proceed via more symmetrical transition states with smaller degrees of proton transfer and Nα-OC (O)Ar bond cleavage, less negative charge development at the β-carbon, and a greater extent of triple bond formation than that for the syn-elimination.",
author = "Bong-Rae Cho and Chung, {Hak Suk} and Cho, {Nam Soon}",
year = "1998",
month = "7",
day = "10",
language = "English",
volume = "63",
pages = "4685--4690",
journal = "Journal of Organic Chemistry",
issn = "0022-3263",
publisher = "American Chemical Society",
number = "14",

}

TY - JOUR

T1 - Elimination Reactions of (E)- and (Z)-Benzaldehyde O-Benzoyloximes. Transition State Differences for the Syn- and Anti-Eliminations Forming Nitriles

AU - Cho, Bong-Rae

AU - Chung, Hak Suk

AU - Cho, Nam Soon

PY - 1998/7/10

Y1 - 1998/7/10

N2 - Elimination reactions of (E)- and (Z)-benzaldehyde O-benzoyloximes 1 and 2 with DBU in MeCN have been investigated kinetically. The reactions are second order and exhibit substantial values of Hammett ρ and kH/kD values, and an E2 mechanism is evident. The rate of elimination from 2 is approximately 36000 fold faster than that from 1. For reactions of 1 with DBU in MeCN, kH/kD = 3.3 ± 0.2, Hammett ρ value of 2.19 ± 0.05, β1g = -0.49 ± 0.02, ΔH‡ = 10.4 ± 0.6 kcal/mol, and ΔS‡ = -34.3 ± 2.6 eu have been determined. The corresponding values for 2 are kH/kD = 7.3 ± 0.2, ρ = 1.21 ± 0.05, β1g = -0.40 ± 0.01, ΔH‡ = 6.8 ± 0.5 kcal/mol, and ΔS‡ = -25.8 ± 1.9 eu, respectively. The results indicate that the anti-eliminations from 2 proceed via more symmetrical transition states with smaller degrees of proton transfer and Nα-OC (O)Ar bond cleavage, less negative charge development at the β-carbon, and a greater extent of triple bond formation than that for the syn-elimination.

AB - Elimination reactions of (E)- and (Z)-benzaldehyde O-benzoyloximes 1 and 2 with DBU in MeCN have been investigated kinetically. The reactions are second order and exhibit substantial values of Hammett ρ and kH/kD values, and an E2 mechanism is evident. The rate of elimination from 2 is approximately 36000 fold faster than that from 1. For reactions of 1 with DBU in MeCN, kH/kD = 3.3 ± 0.2, Hammett ρ value of 2.19 ± 0.05, β1g = -0.49 ± 0.02, ΔH‡ = 10.4 ± 0.6 kcal/mol, and ΔS‡ = -34.3 ± 2.6 eu have been determined. The corresponding values for 2 are kH/kD = 7.3 ± 0.2, ρ = 1.21 ± 0.05, β1g = -0.40 ± 0.01, ΔH‡ = 6.8 ± 0.5 kcal/mol, and ΔS‡ = -25.8 ± 1.9 eu, respectively. The results indicate that the anti-eliminations from 2 proceed via more symmetrical transition states with smaller degrees of proton transfer and Nα-OC (O)Ar bond cleavage, less negative charge development at the β-carbon, and a greater extent of triple bond formation than that for the syn-elimination.

UR - http://www.scopus.com/inward/record.url?scp=0000044590&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0000044590&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:0000044590

VL - 63

SP - 4685

EP - 4690

JO - Journal of Organic Chemistry

JF - Journal of Organic Chemistry

SN - 0022-3263

IS - 14

ER -