Ethoxide Ion In Ethanol Research Articles

How to measure both primary and secondary hydrogen isotope effects in hydrogen abstraction from a substrate having two or more equivalent reactive hydrogen atoms

For a reaction of the type RH/sub n/ + B ..-->.. RH/sub n-1/ + BH, the substrate may be tracer labeled with tritium to give a mixture of RH/sub n/ and RH/sub n-1/T. Determination of the molar activity of BH after a low (< 5%) extent of reaction and of recovered RH/sub n/ after a known extent of reaction permits the precise determination of both the primary and secondary intermolecular kinetic isotope effects. The method is applied to the E2 reaction of PhCHTCH/sub 2/NMe/sub 3//sup +/ with ethoxide ion in ethanol at 40/sup 0/C to give a primary isotope effect of 4.067 +- 0.127 and a secondary isotope effect of 1.311 +- 0.014.

ChemInform Abstract: THE INSTABILITY OF SILVER ALKOXIDES

AbstractDie Umsetzung von Lithium‐ oder Natriummethylat mit einem Moläquivalent Silbernitrat, ‐perchlorat oder ‐tosylat führt in wasserfreiem Methanol bei 25°C zu einem extrem instabilen Produkt, vermutlich Silbermethylat, welches sich rasch zu metallischem Silber und nicht identifizierten Oxidationsprodukten zersetzt.

Equilibria in complexes of N-heterocyclic molecules. Part 8. Reaction of tris(5-nitro-1,10-phenanthroline)ruthenium(II) cation with methoxide and ethoxide ions

Spectroscopic studies show that methoxide ion reacts reversibly with methanolic solutions of the tris(5-nitro-1,10-phenanthroline)ruthenium(II) cation, [RuL3]2+, via addition to the 2 position of each heterocyclic ligand. An analogous addition occurs with ethoxide ion in ethanol, except that with excess of [OEt]– the diethoxy-adduct is precipitated. The kinetics of addition of the first alkoxide ion have been examined in both cases. With methoxide ion the observed rate law, Rate =k1[Ru][OMe–]+k–1[Ru], allows evaluation of both forward and reverse rate constants. For ethoxide ion a simple second-order rate law, Rate =k1[Ru][OEt–], is observed. Comparison with similar data for the related additions of [OH]– and [CN]– ions to [RuL3]2+ shows the relative rate order [OEt]– > [OMe]–[OH]–[CN]–.

The Instability of Silver Alkoxides

Abstract The reaction of silver ion with methoxide ion in methanol or with ethoxide ion in ethanol at 25°C affords highly unstable intermediates (presumably the silver alkoxides) which decompose rapidly to give metallic silver and unidentified oxidation products. Silver salts of tert-butyl alcohol and phenol decompose somewhat more slowly, while phenols with electron-withdrawing groups afford stable silver salts.

Interactions of 1,2,3,5- and 1,2,4,5-tetranitrobenzene with some nucleophiles in protic solvents

In the presence of hydroxide ion or sulphite ion in water, or ethoxide ion in ethanol, 1,2,3,5-tetranitrobenzene gives red complexes which are shown, from 1H n.m.r. measurements, to result from covalent addition of the nucleophile at a hydrogen-carrying ring carbon. The equilibrium constant for the formation of the hydroxide adduct has the value 2·4 × 104 l. mole–1. The solutions are not stable and replacement of the nitro-group at C-2 occurs quickly. The rate constants have been measured. In contrast 1,2,4,5-tetranitrobenzene reacts with hydroxide to give 2,4,5-trinitrophenol without the production of colour. With ethoxide or sulphite ions coloured species are produced whose structures are discussed.

Isotope effect studies on elimination reactions. VII. The stereochemistry of elimination from 2-phenylethylammonium ions

The stereochemistry of the base-promoted elimination reactions of 2-phenylethyltrimethylammonium and 2-phenylethyldimethylanilinium ions has been investigated using both ethoxide ion in ethanol and t-butoxide in t-butyl alcohol as base-solvent systems. The proton magnetic resonance spectroscopic analysis of the deuterated styrene products formed from the reactions of the threo-2-phenylethylammonium-1,2-d2 ions established that elimination proceeds more than 95% by an anti process.

Isotope effect studies on elimination reactions. VI. The mechanism of the bimolecular elimination reaction of 2-arylethylammonium ions

The mechanism of the elimination reaction of 2-arylethyltrimethylammonium ions with ethoxide ion in ethanol has been examined using tracer and kinetic isotope effect techniques. Absence of exchange with solvent of both 2-phenylethyltrimethylammonium-2,2-d2 bromide and 2-(p-trifluoromethylphenyl)-ethyltrimethylammonium-2,2-d2 bromide and the observation of nitrogen isotope effects of 1.3 and 0.9%, respectively, have eliminated a two-step process involving a freely-solvated carbanion intermediate for both salts. The observation of only a slight change in the magnitude of the nitrogen isotope effect when the solvent is changed from ethanol to water has also excluded a zwitterionic intermediate which is specifically hydrogen-bonded to the molecule of ethanol formed by removal of a β-hydrogen by ethoxide ion. Finally, tracer studies using α- and β-dideuterated substrates have eliminated the less probable reaction pathways involving ylide and carbene intermediates. It is concluded that the reaction of 2-arylethyltrimethylammonium salts with ethoxide ion is a concerted E2 process.

The Alkaline Ethanolyses of Chlorophenyldiphenylsulfonium Halides, Chlorophenyl Phenyl Sulfones and Chloronitrobenzene in Aqueous Ethanol

Abstract o-, m-, and p-Chlorophenyldiphenylsulfonium halides were prepared and subjected to the alkaline ethanolysis in order to compare the activating effects of o-, m-, and p-diphenylsulfonio groups with those of o-, m-, and p-phenylsulfonyl and nitro-groups. The diarylsulfonio group at either ortho or para position was found to facilitate the nucleophilic substitution of aryl chloride powerfully. While the effect of diarylsulfonio group was not only substantially larger than that of phenylsulfonyl group, but also exceeding even that of nitro group. Meanwhile, with ethoxide ion in ethanol the alkaline decomposition reaction, presumed to be initiated by the attack of ethoxide on the sulfur atom of chlorophenyldiphenylsulfonium halide, occurred competitively along with the SN reaction, but the rate of the SN reaction of p-chlorophenyldiphenylsulfonium perchlorate was found to be about 9 times larger than that of the decomposition reaction. Substitution of a methyl group at ortho to diphenylsulfonio, phenylsulfonyl and -sulfinyl groups did change very little the rates of the ethanolyses of the corresponding p-substituted chlorobenzenes, suggesting that essentially there is no or little steric inhibition for the 3d-orbital resonance with either sulfonio, sulfinyl, or sulfonyl group in the SN reaction of these compounds.

Kinetics of proton-transfer reaction between 4-nitrobenzyl-cyanide and ethoxide ion in ethanol + ether from –60 to –124°C

The rate of the proton-transfer reaction between ethoxide ion and 4-nitrobenzyl cyanide in ethanol + ether has been determined over the temperature range –60 to –124°C, by a combination of low-temperature and stopped-flow techniques. At the lowest temperatures there are positive deviations, attributed to quantum-mechanical tunnelling. The equations for a symmetrical parabolic energy-barrier have been fitted to the results. The barrier-width for the best fit is 1.62 A, comparable with the values found for other reactions in alcoholic media; the barrier-height is 10.7 kcal mole–1. At the highest temperature the Arrhenius plot shows a negative deviation from linearity, attributable to the preliminary formation of an unstable complex.

Kinetic isotope effect in reaction between 4-nitrobenzyl-cyanide and ethoxide ion in ethanol + ether

The rate of the deuteron-transfer reaction between ethoxide ion and 4-nitrobenzylcyanide-α, α-d2 has been determined at six temperatures over the temperature range –40 to –90°. At the highest temperatures, the Arrhenius plot shows a negative deviation from linearity, and approaches that for the proton-transfer; this behaviour confirms the previous interpretation in terms of an unstable intermediate complex. At lower temperatures (–60 to –90°), the plot for the deuteron-transfer reaction is linear; the energy of activation is 1.85± 0.2 kcal mole–1 higher than for the proton-transfer, and the A-factor is about 5 times larger. These values can be interpreted in terms of tunnelling. On fitting the equations for a parabolic energy-barrier, with ΔH°= 0, we find for the height 10.3 kcal mole–1 and for the width 1.63 A. These are in good agreement with the values found independently from the non-linear Arrhenius plot for the proton-transfer reaction in the same medium (10.7 kcal mole–1 and 1.62 A).

ISOTOPE EFFECT STUDIES ON ELIMINATION REACTIONS: III. NITROGEN ISOTOPE EFFECTS IN THE E2 REACTION OF ETHYLTRIMETHYL-AMMONIUM AND 2-PHENYLETHYLTRIMETHYLAMMONIUM IONS

Nitrogen isotope effects have been determined for the E2 reaction of two quaternary ammonium salts with ethoxide ion in ethanol. Ethyltrimethylammonium iodide gave k14/k15 values of 1.017 at 60° and 1.015 at 95°, while 2-phenylethyltrimethylammonium bromide gave 1.012 at 40° and 1.009 at 60°. These results and the β-deuterium isotope effects reported by others have been interpreted in terms of the relative extent of Cα—N+ and Cβ—H bond weakening in the transition states of the two reactions.

CARBON-13 KINETIC ISOTOPE EFFECTS IN BIMOLECULAR REACTIONS

Carbon-13 kinetic isotope effects have been measured for the bimolecular reaction of 1-phenyl-1-bromoethane (I) and benzyl bromide (II) with alkoxide ion in alcohol solution. Compound I gave an effect, k12/k13, of 1.0032 ± 0.0005 for reaction with ethoxide ion in ethanol, while II gave k12/k13 = 1.0531 ± 0.0004 for reaction with methoxide ion in methanol. These surprisingly different effects are tentatively interpreted in terms of a model for the transition state having varying degrees of ionic character.

Rates, Products and Salt Effects in the Reactions of Benzyldimethylanilinium Ion with Ethoxide Ion in Ethanol

Rates, Products and Salt Effects in the Reactions of Benzyldimethylanilinium Ion with Ethoxide Ion in Ethanol