Substituent Effects in Pyrolysis. V.1,2 A p-σ+ Correlation in the Pyrolysis of 1-Arylethyl Acetates

Taylor, Roger; Smith, Grant Gill; Wetzel, William H.

doi:10.1021/ja00883a037

Cited by 66 publications

(20 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Baker and Nathan142 reported that a Me group provides more stabilization to the developing positive charge at the p‐benzylic position than Et, i‐Pr, and t‐Bu groups in the solvolysis of p‐alkyl substituted benzyl bromides, and attributed this order of reactivity to the greater donating ability of CH bonds compared with that of CC bonds. Although these results are consistent with the trends in34–37 carbon NMR chemical shifts of the β‐carbon in β‐substituted styrenes in solvents of different polarity,143 the opposite trend was found in the gas phase pyrolysis of 1‐arylethyl acetates, which cast a shadow of doubt on the original interpretation of Nathan–Baker effect 144…”

Section: Factors Controlling Hyperconjugationsupporting

confidence: 63%

Hyperconjugation

Alabugin

Gilmore

Peterson

2011

WIREs Comput Mol Sci

288

289

View full text Add to dashboard Cite

This review outlines the ubiquitous nature of hyperconjugative interactions and their role in the structure and reactivity of organic molecules. After defining the common hyperconjugative patterns, we discuss the main factors controlling the magnitude of hyperconjugative effects, including orbital symmetry, energy gap, electronegativity, and polarizibility. The danger of underestimating the magnitude of hyperconjugative interactions are illustrated by a number of spectroscopic, conformational, and structural effects. Through the use of advanced computational techniques, the true role of hyperconjugative effects, as it pertains to their influence on stereoelectronics, conformational equilibria, and reactivities relative to other electronic effects, continue to be uncovered.

show abstract

Section: Factors Controlling Hyperconjugationsupporting

confidence: 63%

Hyperconjugation

Alabugin

Gilmore

Peterson

2011

WIREs Comput Mol Sci

288

289

View full text Add to dashboard Cite

show abstract

“…The least advanced processes are the formation of the H 6 −O 1 bond (33.0%) and the formation of the C 4 −C 5 double bond (30.7%). The dissociation of the O 3 −C 4 (X−C α ) bond before of the C 5 −H 6 (C β −H) bond is in accordance with the proposal of Taylor et al for the 1,5 thermal eliminations, based on the fact that the Hammett ρ values at the α carbon were of larger magnitude than those observed for the β carbon.…”

Section: Resultssupporting

confidence: 91%

Gas-Phase Elimination Reaction of Ethyl (5-cyanomethyl-1,3,4-thiadiazol-2-yl)carbamate: A Computational Study

Vélez

Ruíz

Quíjano

et al. 2015

Int. J. Chem. Kinet.

View full text Add to dashboard Cite

The gas‐phase elimination reaction of ethyl (5‐cyanomethyl‐1,3,4‐thiadiazol‐2‐yl)carbamate has been studied computationally at the MP2/6–31++G(2d,p) level of theory. The values of the activation parameters and rate constants for the thermal decomposition were evaluated over a temperature range from 405.0 to 458.0 K. The temperature dependence of the rate constants was used to deduce the modified Arrhenius expression: log k405–458 K = (9.01 ± 0.49) + (1.32 ± 0.16) log T – (6946 ± 30) 1/T, which is in good agreement with the expression obtained from experimental data. The results confirm that the mechanism is a cis‐concerted elimination that occurs in two steps: The first one corresponds to the formation of ethylene and an intermediate, 5‐(cyanomethyl)‐1,3,4‐thiadiazol‐2‐yl‐carbamic acid, via a six‐membered cyclic transition state, and the second one is the decarboxylation of this intermediate via a four‐membered cyclic transition step, leading to carbon dioxide and the corresponding 1,3,4‐thiadiazole derivative (5‐amino‐1,3,4‐thiadiazole‐2‐acetonitrile). The connectivity of transition states with their respective minima was verified through intrinsic reaction coordinate calculations, and the progress of the reaction was followed by means of Wiberg bond indices, resulting that both transition states have an “early” character, nearer to the reactants than to the products.

show abstract

“…This tran sition state is consistent with the observed first order kinetics, the large negative entropy of activation, the absence of induction periods and of any effect by free radical Inhibitors, and the identity of the product olefins formed (84). Isotope effects Indicate a large amount of carbon-hydrogen bond breaking in the transition state (83), whereas the rho value (0.3) for the 2-arylethylacetates at 377° Indicates a small amount of negative charge buildup on the beta-carbon atom (85). A rho value of -0.66 measured for the pyrolysis of the 1-arylethylacetates at 327° (following o-"*" relationship) (85) and a rate acceleration by electronegatlvely substituted aryl esters (86) indicates a small degree of charge separation on the alpha-carbon.…”

Section: H-c-c+supporting

confidence: 84%

Syntheses and eliminations of cyclopentyl derivatives

Rausch

View full text Add to dashboard Cite

Substituent Effects in Pyrolysis. V.^1,2 A p-σ⁺ Correlation in the Pyrolysis of 1-Arylethyl Acetates

Cited by 66 publications

References 0 publications

Hyperconjugation

Hyperconjugation

Gas-Phase Elimination Reaction of Ethyl (5-cyanomethyl-1,3,4-thiadiazol-2-yl)carbamate: A Computational Study

Syntheses and eliminations of cyclopentyl derivatives

Contact Info

Product

Resources

About