Attack Of Methoxide Ion Research Articles

Reaction of methoxide ion with the Z‐ and E‐isomers of O‐methylbenzohydroximoyl cyanide. Theoretical calculations on the conformations of the tetrahedral intermediate

Theoretical calculations (HF/6–31 + G*, MP2/6–31 + G*//HF/6–31 + G*, B3LYP/6–31 + G*//HF/6–31 + G*, HF-SCIPCM/6–31 + G*//HF/6–31 + G*, and B3LYP-SCIPCM/6–31 + G*//HF/6–31 + G*) were carried out on the tetrahedral intermediate RC(CN)(OCH3)—NOCH3 −, where R = C6H5, CH2CH or H, generated by nucleophilic attack of methoxide ion on (Z)- or (E)-O-methylhydroximoyl cyanide [RC(CN)NOCH3]. These calculations indicate that the staggered conformation 4C, which would lead to an E-substitution product, is approximately 7 (R = H) or 8 kcal mol−1 (R = CH2CH) less stable than conformation 4A, which leads to a Z-substitution product. Furthermore, the lowest energy transition state leading to a Z-substitution product is approximately 5 kcal mol−1 lower in energy than the lowest energy transition state leading to an E-substitution product. These results provide an explanation for the experimental results reported recently that (Z)-O-methylbenzohydroximoyl cyanide gives only the less thermodynamically stable Z-substitution product under conditions where the purported tetrahedral intermediate should have a long enough lifetime to establish an equilibrium between all the staggered conformations. Copyright © 1999 John Wiley & Sons, Ltd.

Reaction of methoxide ion with theZ- andE-isomers ofO-methylbenzohydroximoyl cyanide. Theoretical calculations on the conformations of the tetrahedral intermediate

Theoretical calculations (HF/6–31 + G*, MP2/6–31 + G*//HF/6–31 + G*, B3LYP/6–31 + G*//HF/6–31 + G*, HF-SCIPCM/6–31 + G*//HF/6–31 + G*, and B3LYP-SCIPCM/6–31 + G*//HF/6–31 + G*) were carried out on the tetrahedral intermediate RC(CN)(OCH3)—NOCH3−, where R = C6H5, CH2CH or H, generated by nucleophilic attack of methoxide ion on (Z)- or (E)-O-methylhydroximoyl cyanide [RC(CN)NOCH3]. These calculations indicate that the staggered conformation 4C, which would lead to an E-substitution product, is approximately 7 (R = H) or 8 kcal mol−1 (R = CH2CH) less stable than conformation 4A, which leads to a Z-substitution product. Furthermore, the lowest energy transition state leading to a Z-substitution product is approximately 5 kcal mol−1 lower in energy than the lowest energy transition state leading to an E-substitution product. These results provide an explanation for the experimental results reported recently that (Z)-O-methylbenzohydroximoyl cyanide gives only the less thermodynamically stable Z-substitution product under conditions where the purported tetrahedral intermediate should have a long enough lifetime to establish an equilibrium between all the staggered conformations. Copyright © 1999 John Wiley & Sons, Ltd.

Mechanism of formation of (methoxy)(amino) — and bis(amino) carbene complexes by nucleophilic attack of methoxide ion and amines on platinum(II)-coordinated isocyanide in anhydrous methanol

The isocyanide complexes [Pt(CNC6H11)(R)(dppe)]ClO4 (R = C4H3N2-C2, 2-pyz; C5H4N-C4, 4-py) undergo nucleophilic attack on the coordinated isocyanide by methoxide ion in acid-base equilibrium with triethylamine in anhydrous methanol, leading to the (methoxy)(amino)carbene species [Pt{C(NHC6H11)OMe}(R)(dppe)]+ by a bimolecular, second-order path. When a primary or secondary amine is used instead of triethylamine, concomitant formation of (methoxy)(amino)- and bis(amino)carbene complexes takes place via parallel, second-order paths involving nucleophilic attack by both methoxide and amine on the isocyanide. A marked solvent effect depressing the rates in comparison to those of the corresponding reactions of amines in chlorinated solvents is observed. No substantial difference in reactivity between the two metal substrates can be detected, indicating the lack of anchimeric assistance to proton transfer from the entering amine to the isocyanide nitrogen, possibly replaced by a solvent mediated pathway. The methoxide ion proves a much better nucleophile than amines in this type of reaction. The interconversion of (methoxy)(amino)- with bis(amino)carberie species via methoxy—amine exchange is extremely slow.

Reaction of 1-chloroperfluorocycloalkene derivatives with nucleophiles

1-Acetyl-2-chloroperfluorocycloalkenes and 1-benzoyl-2-chloroperfluorocycloalkenes have been prepared by the coupling of 2-chloroperfluorocycloalkenyl copper reagent with acetyl chloride and benzoyl chloride, respectively. Similarly, 1-chloro-2-( p-nitrophenyl)perfluoro-cyclopentene and -cyclohexene were prepared by the reaction of 2- chloroperfluorocyclo-pentenyl and -hexenyl copper reagent with p-nitroiodobenzene. The compounds contain not only highly activated double bonds but also charge-stabilizing groups in vinylic positions. The reaction of these compounds has been studied with various nucleophiles. They were very susceptible to nucleophilic attack at the chlorine-bonded carbon atom. Cyclobutene and cyclopentene derivatives underwent interesting nucleophilic displacement reactions of vinylic chlorine with alkoxide, amine and triethyl phosphite without allylic rearrangement under mild conditions. The stabilization effect to the generated carbanion intermediate by the acyl or p-nitrophenyl group undoubtedly dictates selectivity. However, additional factors must be considered in cyclohexene derivatives in which both ‘inward' and ‘outward' eliminations occur from methoxide ion attack on perfluoroacyclohexene derivatives. Also the order of activating power for a double bond has been found to be benzoyl > acetyl ⪢ p-nitrophenyl and 1-chlorotetfluorocyclobutene derivatives were more reactive than 1-chlorohexafluorocyclopentene derivatives towards the various nucleophiles.

Catalysis by alkali and alkaline-earth metal ions in nucleophilic attack of methoxide ion on crown ethers bearing an intra-annular acetoxy group

Rates of reaction of methoxide ion with crown ethers bearing an intra-annular acetoxy group are markedly enhanced by alkali and alkaline-earth metal bromides as a result of much stronger interactions of the metal ions with transition states than with reactants.

The methanolysis kinetics and dissociation constants of 1-(subst. benzoyl)-3-phenylthioureas

A series of seven 1-(subst. benzoyl)-3-phenylthioureas have been prepared and their dissociation constants and solvolysis rate constants have been measured in methanol at 25 °C. The reaction constants found show that the solvolysis rate is limited by the attack of methoxide ion on the benzoyl carbonyl group of the non-dissociated substrate. The polar effect of substituents in benzoyl group is extensively transferred also by the intramolecular hydrogen bond.

Regiospecific attack of methoxide ion on 4-alkoxy-o-quinone imines. A novel route to p-quinone monoacetals

In the solvolysis of 4-alkoxy-5-methyl-o-benzoquinone N-arylsulphonylimines (1a) and (1b)(NaOH-MeOH–H2O), the regiospecific attack of MeO– occurs initially on the carbon atom substituted by the alkoxy-group to produce the p-benzoquinone monoacetals (3a) and (3b), respectively.

Concurrent methoxide ion attack at the 5- and 7-carbons of 4-nitrobenzofurazan and 4-nitrobenzofuroxan. A kinetic study in methanol

Concurrent methoxide ion attack at the 5- and 7-carbons of 4-nitrobenzofurazan and 4-nitrobenzofuroxan. A kinetic study in methanol

Trifluoromethylsulfonyl aryl derivatives: competitive nucleophilic attack at an aromatic carbon and at the sulfur atom of an aromatic SO2CF3 group

The reaction of methoxide ion with 2-nitro-4-trifluoromethylsulfonylanisole, 4-nitro-2-triftuoromethylsulfonylanisole and 2,4- bis(trifluoromethylsulfonyl)anisole in DMSO has been studied by 1H and 19F nmr. Evidence for the transient formation of gem-dimethoxy σ-adducts arising from nucleophilic attack at the aromatic C1 carbon is given. Concurrent methoxide ion attack occurs at the sulfur atom of the SO2CF3 group to give the aryl methyl sulfonates ArSO3CH3, which are slowly converted into aryl sulfonates ArSO3−. The 1H chemical shifts of the anisoles are consistent with a greater electron-withdrawing effect of the SO2CF3 group compared to the nitro group. In contrast, a 4-nitro group appears to be more efficient than a 4-SO2CF3 group in delocalizing the negative charge of the σ-adducts.

Heterocyclic Meisenheimer complexes: kinetic and equilibrium data for methoxide ion attack on various disubstituted 2,4-Y,Z-thiophenes and -selenophenes in methanol

Heterocyclic Meisenheimer complexes: kinetic and equilibrium data for methoxide ion attack on various disubstituted 2,4-Y,Z-thiophenes and -selenophenes in methanol

High resolution nuclear magnetic resonance studies of chemical reactions using flowing liquids. Kinetic and thermodynamic intermediates formed by the attack of methoxide ion on 1-X-3,5-dinitrobenzenes

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTHigh resolution nuclear magnetic resonance studies of chemical reactions using flowing liquids. Kinetic and thermodynamic intermediates formed by the attack of methoxide ion on 1-X-3,5-dinitrobenzenesColin A. Fyfe, Michael Cocivera, and Sadru W. H. DamjiCite this: J. Am. Chem. Soc. 1975, 97, 20, 5707–5713Publication Date (Print):October 1, 1975Publication History Published online1 May 2002Published inissue 1 October 1975https://doi.org/10.1021/ja00853a012RIGHTS & PERMISSIONSArticle Views87Altmetric-Citations13LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (776 KB) Get e-Alerts Get e-Alerts

Investigations into the stereochemistry of nucleophilic attack on olefins coordinated to palladium(II) and platinum(II)

A study of the oxidative hydrolysis of olefins in the presence of [Pd(dien)H 2O] 2+ and [Pd(en)(H 2O) 2] 2+ (dien = diethylenetriamine, en = ethylenediamine) has indicated that where possible nucleophilic attack on the olefin by hydroxide ion involves prior coordination of the hydroxide to palladium(II). However where no coordination site cis to the olefin is available, as in [Pd(dien)(olefin)] 2+ in neutral solution, direct attack on the olefin by hydroxide ion occurs without prior coordination. Such attack is very slow compared to that involving prior cis-coordination. Some unsuccessful experiments to establish the stereochemistry of methoxide ion attack on preformed platinum(II)—olefin complexes are reported and reasons for their failure discussed.

ChemInform Abstract: HIGH RESOLUTION NUCLEAR MAGNETIC RESONANCE STUDY OF CHEMICAL REACTIONS USING FLOWING LIQUIDS, KINETIC AND THERMODYNAMIC INTERMEDIATES FORMED BY THE ATTACK OF METHOXIDE ION ON 3,5‐DINITROCYANOBENZENE

Equipment and techniques have been developed which make possible the measurement of high resolution n.m.r. spectra in rapidly flowing, chemically reacting systems, and have been used to characterize the kinetically formed intermediate complex as well as the thermodynacically stable one from the attack of methoxide ion on 3,5-dinitrocyanobenzene.

High resolution nuclear magnetic resonance study of chemical reactions using flowing liquids: kinetic and thermodynamic intermediates formed by the attack of methoxide ion on 3,5-dinitrocyanobenzene

Equipment and techniques have been developed which make possible the measurement of high resolution n.m.r. spectra in rapidly flowing, chemically reacting systems, and have been used to characterize the kinetically formed intermediate complex as well as the thermodynacically stable one from the attack of methoxide ion on 3,5-dinitrocyanobenzene.

Formation of platinum–carbon σ-bonded complexes from co-ordinated and unco-ordinated olefins and acetylenes

Nucleophilic attack of methoxide ion on olefinic and acetylenic groups of unsaturated phosphine complexes of PtII occurs even when the group is not co-ordinated to the metal; structures of the resulting cyclic σ-bonded complexes are suggested.