Chemistry Of Crown Ethers Research Articles

Chemistry of crown ethers. Part XXI. Association constants of the complexes of 18‐crown‐6 with dimethyl sulfate, dimethyl carbonate and dimethyl oxalate

AbstractThe association constants (K) of the complexes of 18‐crown‐6 with dimethyl sulfate, dimethyl carbonate and dimethyl oxalate have been determined by a 1H NMR method. The K values of these complexes were found to be 0.6, 0.8 and 0.6 l/mol, respectively, which values are several orders of magnitude lower than those reported for crown ether/ammonium salt complexes.

ChemInform Abstract: PROGRESS IN CROWN ETHER CHEMISTRY. PART IV C

Chemischer InformationsdienstVolume 13, Issue 30 Reviews ChemInform Abstract: PROGRESS IN CROWN ETHER CHEMISTRY. PART IV C E. WEBER, E. WEBERSearch for more papers by this author E. WEBER, E. WEBERSearch for more papers by this author First published: July 27, 1982 https://doi.org/10.1002/chin.198230337AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume13, Issue30July 27, 1982 RelatedInformation

Chemistry of crown ethers. XVII. Triphase catalysis by immobilized benzo‐18‐crown‐6

AbstractSeveral immobilized benzo‐18‐crown‐6 derivatives have been synthesized and a study has been made of their activities as triphase catalysts in the reaction between 1‐bromooctane in toluene and aqueous potassium cyanide. In each case the reaction rate was proportional to the 1‐bromooctane concentration and to the amount of catalyst and also depended on the potassium cyanide concentration. Under non‐stirred conditions the activity per crown ether moiety was dependent on the degree of functionalization of the supporting polymer, being high for a highly substituted polystyrene/divinylbenzene resin and low for a sparingly substituted one. The beneficial effect of the high loading disappeared completely, however, under stirred conditions. The triphase catalyst can be used both with liquid‐liquid‐solid and with solid‐solid‐liquid systems and can be recovered without significant loss of activity.

Chemistry of crown ethers (XVI). A safe and efficient procedure for the isolation and purification of crown ethers by complex formation with alkaline earth metal alkanedisulfonates

AbstractA safe, efficient and selective method has been developed for the isolation and purification of crown ethers to replace the conventional procedure, which involves repeated vacuum distillations and has reportedly led to destructive explosions. The method is based on the formation of an insoluble 1:1 complex upon stirring a solution of a crown ether in an organic solvent with solid metal salts of 1,n‐alkanedisulfonic acids, such as barium and strontium methanedisulfonate and barium 1,2‐ethanedisulfonate. This extraction procedure can be applied to several crown ethers (including 18‐crown‐6) dissolved in a variety of solvents. Almost quantitative recovery of the crown ether is achieved by continuous extraction with nitromethane.The usefulness of the method was illustrated by isolating 18‐crown‐6 from the crude mixture obtained in the course of its preparation. Whereas conventional workup (including two distillation steps) gave a 25% yield of pure 18‐crown‐6, the CH2(SO3)2Ba‐based method gave a yield of 34%.

ChemInform Abstract: PROGRESS IN CROWN ETHER CHEMISTRY. (PART IV A)

Chemischer InformationsdienstVolume 11, Issue 49 Reviews ChemInform Abstract: PROGRESS IN CROWN ETHER CHEMISTRY. (PART IV A) F. + VOEGTLE, F. + VOEGTLESearch for more papers by this authorE. WEBER, E. WEBERSearch for more papers by this authorU. ELBEN, U. ELBENSearch for more papers by this author F. + VOEGTLE, F. + VOEGTLESearch for more papers by this authorE. WEBER, E. WEBERSearch for more papers by this authorU. ELBEN, U. ELBENSearch for more papers by this author First published: December 9, 1980 https://doi.org/10.1002/chin.198049345AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume11, Issue49December 9, 1980 RelatedInformation

ChemInform Abstract: CHEMISTRY OF CROWN ETHERS‐ THE MASS SPECTRA OF MACROCYCLIC POLYETHERS

Chemischer InformationsdienstVolume 8, Issue 15 Physical Organic Chemistry ChemInform Abstract: CHEMISTRY OF CROWN ETHERS- THE MASS SPECTRA OF MACROCYCLIC POLYETHERS R. T. GRAY, R. T. GRAYSearch for more papers by this authorD. N. REINHOUDT, D. N. REINHOUDTSearch for more papers by this authorK. SPAARGAREN, K. SPAARGARENSearch for more papers by this authorJ. F. DE BRUIJN, J. F. DE BRUIJNSearch for more papers by this author R. T. GRAY, R. T. GRAYSearch for more papers by this authorD. N. REINHOUDT, D. N. REINHOUDTSearch for more papers by this authorK. SPAARGAREN, K. SPAARGARENSearch for more papers by this authorJ. F. DE BRUIJN, J. F. DE BRUIJNSearch for more papers by this author First published: April 12, 1977 https://doi.org/10.1002/chin.197715044AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume8, Issue15April 12, 1977 RelatedInformation

Chemistry of crown ethers: the mass spectra of macrocyclic polyethers

A detailed evaluation of the mass spectral fragmentation patterns of several series of crown ethers has been made. Included are compounds containing one or two aromatic or heteroaromatic rings linked through carbon atoms to polyether chains of various lengths. Although such molecules are highly functionalized and have high molecular weights, molecular ion peaks were always observed, and a large percentage of the total ion current was carried by a small number of fragment ions. Only small differences were observed in the mass spectra of compounds having different aromatic ring substitution patterns. The fragmentation patterns for each set of compounds pointed to the formation of fragment ions in which the positive charge was localized on: (i) ions containing only polyether ring carbon and oxygen atoms; in the majority of cases such an ion (protonated ethylene oxide at m/e 45) provided the base peak: (ii) ions containing the aromatic (heteroaromatic) nucleus and no polyether ring carbon atoms; (iii) ions containing the aromatic (heteroaromatic) nucleus together with part of the polyether chain. High resolution measurements and metastable analysis provided confirmation for the postulated fragmentation mechanisms and product ion structures. Hydrogen and carbon rearrangements are involved in some cases. Components of higher molecular weight crown ether mixtures have been identified by mass spectrometry on the basis of their molecular ion peaks.

Chemistry of crown ethers: Complexation with alkali metal trichloro(ethylene)platinum(II) salts

A novel method has been developed for the determination of the complexation constants of crown ethers with alkali salts. It comprises the equilibration of crown ether ( 1–7) solutions in deuterochloroform with solid trichloro(ethylene)platinum(II) salts (Na +, K +, Rb +, Cs +) and the PMR spectroscopic determination of the equilibrium ratio of complex to free crown ether from the relative intensities of the ethylene and crown ether protons. The solubility of uncomplexes salt was determined independently by atomic absorption spectrometry. The major advantages of this method over others are: (i) complexation constants in apolar solvents are obtained from a direct solid-liquid transition, (ii) the cation in the salt can be varied, and (iii) a simple detection technique can be used for monitoring the complexation. The PMR spectra indicate that there are three types of complex, depending on the ratio of the diameter of the crown ether cavity to that of the cation. If this ratio is small (<1), the aromatic ring is almost perpendicular to the flat polyether ring. With increasing ratio (∼1.0) the flat polyether ring and the aromatic ring become almost coplanar in the complex. If the ratio is large (>1.0) the polyether ring is twisted around the cation.

Chemistry of crown ethers: Synthesis of crown ethers derived from α,γ‐and α,δ‐bis(halomethyl)‐ or α,γ‐bis(hydroxymethyl)‐substituted aromatics

AbstractThree series of novel crown ethers have been prepared in which polyether rings of various sizes are linked to a benzene ring through the 1,3‐ or 1,4‐positions or to a furan ring through the 2,5‐positions. They were synthesized from the corresponding α,γ‐ or α,δ‐bis(halomethyl)‐substituted aromatics by reaction with polyethylene glycol disalts or from the disalts of bis(hydroxymethyl)‐substituted aromatics by reaction with polyethylene glycol ditosylates. Both 1:1 (2−67 % yield) and 2:2 (6−30% yield) cyclic reaction products were formed.The fact that the above compounds, which may contain up to 31 ring atoms, are obtained in such high yields without operating at high dilution is connected with the relationship between the chain length of the polyethylene glycol and the diameter of the cation used in the synthesis (template effect).

Chemistry of crown ethers: Synthesis of crown ethers based on α,β-bis(halomethyl)- or α,β-bis(hydroxymethyl)-substituted aromatics

Two types of novel crown ethers in which a polyether chain is linked, via C atoms, with two adjacent C atoms of an aromatic or heteroaromatic ring have been synthesized by reaction of α,β-bis(halomethyl)-substituted aromatics with polyethylene glycolates. Both 1:1 and 2:2 cyclic reaction products were formed, in yields varying from 1 to 53% and from 0 to 24%, respectively. The relatively high yields of these macrocyclic polyethers (rings containing from 11 to 34 atoms), obtained without operating at high dilution, depend both on the chain length of the glycol and on the nature of the cation. This can be explained in terms of a “template” effect of the cation in the cyclization step. Experimental evidence supporting such an effect was obtained from the relationship between the 1:1 product selectivity and the glycol chain length for cations with different ionic radii (L +, Na + and K +). Furthermore, a correlation has been established between the ratio of the yields of 1:1 and 2:2 cyclic products from the reaction of 1,2-bis(bromomethyl)benzene and dipotassium triethylene glycolate and the ratio of the relative complexation constants of these compounds with potassium salts.

Principles and Synthetic Applications in Crown Ether Chemistry

The principles involved in macroheterocycle chemistry are discussed. Classes and types of macroheterocycles, synthetic approaches (including the template effect), complexation and complexes are mentioned. The utilization of crown ethers in synthetic organic chemistry is also surveyed. 1. Introduction 1.1. History 1.2. Nomenclature and Characteristics 1.3. Classes of Crowns and Related Molecules 2. Synthetic Access 2.1. Templated Syntheses 2.2. Non-Williamson Syntheses 3. Complexation 3.1. The Complexation Phenomenon 3.2. Types of Complexes 4. Synthetic Utility 4.1. Solubilization and Phase Transfer 4.2. Cation Effects 4.3. Crowns as Reagents and Catalysts 4.4. Complexation Specificity 5. Toxicity 6. Conclusions

Crown ether chemistry. Substitution reactions of potassium halide and potassium hydroxide complexes of dicyclohexyl-18-crown-6

Crown ether chemistry. Substitution reactions of potassium halide and potassium hydroxide complexes of dicyclohexyl-18-crown-6