Anionenaktivierung, III. Zur Bedeutung von Wasserstoffbrückenbindungen für das reaktive Verhalten von Kronenäthern und Aminopolyäthern / Anionactivation, III. Anionactivation, III¹ Concerning the Significance of Hydrogen-Bonding for the Reactivity of Crown Ethers and Aminopolyethers

Abstract

Adducts of macrocyclic polyethers (crown ethers) and aminopolyethers1,2 having hydrogen bonds with polar organic molecules, especially with CH-acidic compounds, are described. These can be isolated as solids, and are, as a rule, stoichiometrically consistent. The chemical shift of the 1H NMR signals of the adducts of malononitrile with various crown ethers corresponds to the anionic reactivity of potassium complexes of the crown ethers in the course of nucleophilic substitution reactions.

Geometries, interaction energies and complexation free energies of 18-crown-6 with neutral molecules

“…It was subsequently characterised by Knöchel and co-workers 40 who reported a stoichiometry of 1:1.6. The crystalline 1:2 complex contains the 18C6:(acetonitrile) 2 centrosymmetric moiety, and is dimorphic.…”

Reaction of crown ethers with five-membered heterocycles: 1H-imidazole-4,5-dicarbonitrile, 3-nitro-1,2,4-triazole, and 1H-tetrazole

“…The crystalline supramolecular compounds of crown ethers with heterocycles are stabilized by hydrogen bonds either through one of the above-mentioned substituents in the heterocycle [5][6][7][8][9][10][11][12] or the cyclic ammonium group of the protonated heterocycle [13]. A single example of the formation of a crystalline supramolecular compound of the most effective [3,14] crown ether 1b with unsubstituted triazole is known [15].The aim of this work was to determine the possibility of synthesizing uncharged crystalline supramolecular compounds of various crown ethers with five-membered aromatic heterocycles, containing one proton at each of two adjacent proton-donating atoms separated by one covalent bond and securing stabilization of the supramolecular compound by analogy with the data in [15].It was established that the crystalline supramolecular compounds [1b·4]-7, [2·4]-8, [3·2(4)]-9, [1a·5]-10, [1b·2(5)]-11, [2·2(5)]-12, [3·2(5)]-13, and [3·2(6)]-14 respectively are formed during spontaneous evaporation of the solvents from solutions of the crown ethers 1-3 with the respective heterocycles 4-6. …”

“…The crystalline supramolecular compounds of crown ethers with heterocycles are stabilized by hydrogen bonds either through one of the above-mentioned substituents in the heterocycle [5][6][7][8][9][10][11][12] or the cyclic ammonium group of the protonated heterocycle [13]. A single example of the formation of a crystalline supramolecular compound of the most effective [3,14] crown ether 1b with unsubstituted triazole is known [15].…”

“…An indispensable condition for the formation of crystalline supramolecular compounds [1, 2] of crown ethers with organic molecules is the presence in the latter of proton-donating centers with one of the atoms C, N, or O, particularly H 2 N-, H 2 NSO 2 -, H 2 NCS-, H 2 NHNCO-, H 2 C=, H 3 C-, H 3 CO-, and similar groups or water molecules [1][2][3], securing stabilization of the components of the supramolecular compound by hydrogen bonds. As a rule a pair of protons of the substituent takes part in bonding, and the stability of the compounds decreases in the following order: OH > NH 2 > CH 2 [4].…”

A 1:1 Host-Guest Complex between 1,4,7,10,13,16-Hexaoxacyclooctadecane ('18-crown-6') and m-Nitroaniline: Mere Stoicheiometry or a Genuine 1:1 Adduct ?

“…A number of crystalline complexes of 18-crown-6 with neutral H bond donors R-NH2 or have been prepared during the last decade [1][2][3][4]. Their structural analyses proved them to be 1:2 adducts [e.g.…”