Nucleophilic Properties Research Articles

The imidate–amide rearrangement: an explanation for the ambident nucleophilic properties of neutral amides

Rearrangement of N-methylbenzimidates to tertiary amides (in nitrobenzene at 138°) is readily catalysed by alkyl halides and other electrophilic species, suggesting that alkylation of neutral amides usually proceeds at the O-atom, with N-substitution arising from a subsequent rearrangement.

Demonstration of the relative nucleophilic properties of aromatic primary amines

It is possible to demonstrate this simple nucleophilic substitution by examining the initial stages of the methylation of aniline and other aromatic amines.

Reactivity of vinyl sulphonic esters. Part IV. Evidence of an S N1-type mechanism involving an ethylenic carbon atom

The rate of decomposition of trans-2-phenylthio-1,2-di-p-tolylvinyl 2,4,6-trinitrobenzenesulphonate both in inert and in nucleophilic solvents at 25 °C follows first-order kinetics. The rate depends on the polarity of the reaction medium and not on its nucleophilic properties. Addition of lithium perchlorate enhances the rate by a ‘normal’ salt effect in acetone and methanol and by a ‘special’ salt effect in acetic acid. Common-ion retardation by addition of lithium trinitrobenzenesulphonate (LiTNBS) and radioactive intake into the reacting substrate using 35S labelled lithium trinitrobenzenesulphonate is observed in acetone.

Anomalous nucleophilic properties of anions of nitro-compounds

1. The kinetics of the dissociation of nitroethane under the action of water at various temperatures was studied. The enthalpies and entropies of activation of this process were determined. 2. The kinetics of the decomposition of 2-methyl-2-isopropanol-1 was studied, and the equilibrium constant and rate constant of the addition of the 2-nitropropane anion to formaldehyde at 25° with ionic strength 0.5 were determined. 3. The energies and entropies of activation were found for the process of addition of the 2-nitropropane anion to formaldehyde. 4. The anomalous ratio of the basicity and nucleophilicity of the carbanions of mono- and dinitrocompounds with respect to carbon and hydrogen was demonstrated.

Chemistry of Stable α‐Halogenoorganolithium Compounds and the Mechanism of Carbenoid Reactions

AbstractSome years ago we found that α‐halogenoorganolithium compounds (carbenoids) previously postulated as transient intermediates in organolithium‐initiated α‐eliminations can be obtained in a stable form. The present paper is a review of the methods for their preparation and of their reactivity. They possess both nucleophilic and electrophilic properties, which can be utilized singly or combained for the synthesis of substances of very different types. Their thermolability, which is considerably reduced (with only one known exception) by the solvent tetrahydrofuran, is due to electrophilic secondary reactions, in which carbenes evidently do not occur as intermediates. A mechanism is proposed which fits the experimental data for various carbenoid reactions.

Reactions of the Carbonyl Group in Fluorinated Ketones

AbstractThe chemistry of polyfluorinated ketones has recently received a great deal of attention. A. Ya. Yakoubovich, Usp. Chim. 25, 3 (1956). H. P. Braendlin and E. T. McBee in: Advances in Fluorine Chemistry. Butterworths, London 1963, Vol. 3, p. 1. The review by Braendlin and McBee [2] does not deal only with perfluorinated ketones; moreover, though published in 1963, it is already outdated. The papers discussed in [1,2] will not be reviewed in the present article. . The carbonyl and imino groups of the fluorinated ketones and their imines react in many different ways. In particular, the electron‐attracting perfluoroalkyl groups intensify the electrophilic properties and weaken the nucleophilic properties of the carbonyl group. The perfluoroalkyl group also hinders the heterolytic removal of the hydroxyl group from adducts by reducing the stability of the carbonium ion . The increased electrophilicity of the carbonyl group and the increased stability of the addition products leads not only to a change in reactivity in the characteristic ketone reactions, but also to numerous new reactions which are not observed with non‐fluorinated ketones. Thus it is possible to synthesize a wide variety of fluoroorganic compounds from perfluorinated ketones.We have been concerned mainly with hexafluoroacetone, since in addition to being the most readily available and simplest perfluorinated ketone, this is also a typical representative of this class of compounds. .

A study of the hydrobrominolysis of glycine esters

1. A method is presented for determining hydrobrominolysis rate based on amount of glycine formed, employing chromatography of the reaction mixture with subsequent colorimetry. 2. With increase in nucleophilic properties of the alkyl residue, glycine esters hydrobrominolysis rate increases.

Addition reactions of imenes

AbstractImenes most readily add amines and other nucleophilic reagents, such as water, alcohols, mercaptans, hydrogen sulphide, hydrocyanic acid. Bis‐methylsulphonyl‐N‐methylimene, which was studied more extensively, proved to possess not only electrophilic but also nucleophilic properties. Thus it adds HCl and can be applied in the Friedel‐Crafts reaction.