Crown Ethers And Cryptands

This book introduces the broad and basic principles of crown ether and cryptand chemistry at the advanced undergraduate, graduate and working professional level.

Since the discovery of crown ethers by Pedersen in 1967, several thousands of crown ethers and analogous compounds have been synthesized. Their specific characteristics have been investigated and a variety of applications developed. These developments have led to new fields of chemistry called host-guest chemistry and supramolecular chemistry. This book presents the state-of-the-art of the chemistry of crown ethers and analogous compounds. The first chapter provides an orientation in the new fields of chemistry. Chapter 2 reviews advances in synthetic procedures for crown ethers and analogous compounds including azacrown ethers, thiacrown ethers, functionalized crown ethers, cryptands and others. The focus of chapter 3 is on the concept and synthetic strategies for the molecular design of new crown compounds. Chapters 4-7 are concerned with noteworthy topics in the applications of crown compounds. Chapter 4 deals with the application to ion-selective electrodes and liquid chromatography, both of which are the most important targets in the analytical application of crown compounds. One major application of crown ethers is the design and syntheses of artificial molecules which can catalyze a useful synthetic reaction in an enzyme-mimetic reaction manner, through novel non-covalent complexes. The strategies for enzymatic modelling with crown ethers are covered in chapter 5, while chapter 6 presents the principle of amine-selective colour complexation and its application. In chapter 7 switched-on crown ethers that can respond to environmental stimuli are reviewed. The final chapter is devoted to a wide-ranging discussion of developments in macrocyclic polyamine chemistry. Unlike crown ethers, macrocyclic polyamines, bearing nitrogen donor atoms which belong to a soft base, form complexes with ions of transition metals and heavy metals which are classified as soft acids. Therefore, macrocyclic polyamines are expected to have very versatile applications. Scientists in chemistry, biochemistry, physical organic chemistry, pharmaceutical chemistry and industrial chemistry will find this book a helpful summary and a stimulating contribution to research in this specialized field of crown compounds.

Cryptands were introduced by Jean-Marie Lehn in 1969 as cage-shaped selective ligands for alkali and alkaline-earth metal ions, which lie at the heart of supramolecular chemistry. This book reports on much of the research in the field since the '70s, and looks at, amongst other topics, metal coordination chemistry, anion coordination chemistry, the encapsulation and taming of reactive anions, the formation of cascade complexes and the design of fluorescent sensors for ionic analytes. Cryptands and Cryptates has been written as a coursebook, structured as a series of lectures for graduate students or advanced researchers in chemistry, materials science, chemical biology and nanotechnology. It is fully illustrated to show experiments and results, and is intended to stimulate further interest in this fertile field of supramolecular chemistry. Chapters are preceded by a Foreword by Jean-Marie Lehn. Contents: The Beginning of the Story: Crown EthersThe Birth of Cryptands and CryptatesRecognition of the Radius of s-Block Metal Ions by CryptandsCompetitive Hosts for Alkali Metal Ions: Spherands and DerivativesThe Coordination Chemisty of Ammonium and OxoniumThe Age of Anion Coordination ChemistryThe Appearance of Bistren CryptandsBistren Cryptands Grow and MultiplyThe Formation of Dicopper(II) Bistren Cryptates and the Nature of Their Cavity Anion Recognition by Dicopper(II) Bistren Cryptates: The Geometrical FactorAnion Fluorescence Sensing by Dimetallic Bistren Cryptates: The Fluorophore–Spacer–Receptor ParadigmAnion Fluorescence Sensing by Dimetallic Bistren Cryptates: The Indicator Displacement ParadigmNucleotide Recognition and Sensing by a Dicopper(II) Bistren CryptateAnion Inclusion by Hexaprotonated Bistrens: HalidesAnion Inclusion by Hexaprotonated Bistrens: OxoanionsRecognition of Linear Dicarboxylates: The Hydrogen Bonding vs Metal–Ligand Interactions ContestBistren Amides: Neutral Receptors That Recognise Anions Only Through Hydrogen Bonding InteractionsThe Taming of Peroxide (By a Bistren Amide Cryptand)Coordination Chemistry of the Smallest Bistren CryptandSize Exclusion Selectivity: The Case of FluoridePseudo-Cryptands: Closing the Receptor's Cavity with a Transition MetalUse of Cryptands to Make Automatic Molecular BurettesCages in Everyday Life, Chemistry and Art Readership: Graduate students or advanced researchers in chemistry, materials science, chemical biology and nanotechnology. Keywords: Supramolecular Chemistry;Coordination Chemistry of Alkali Metal Ions;Transition Metal Coordination Chemistry;Anion Coordination Chemistry;Crown Ethers;Cryptands;Bistren Cryptands;Recognition of Anions and of Metal Ions;Fluorescent Sensing of Anions and Metal Ions;Encapsulation of Reactive AnionsReview: Key Features: While review articles have been published on partial aspects of this topic, no books have been devoted to an overall and homogeneous treatment of 'cryptands and cryptates'

An advanced-level textbook of organic chemistry for the graduate (B.Sc) and postgraduate (M.Sc) students of Indian and foreign universities. This book is a part of the four-volume series, entitled “A Textbook of Organic Chemistry – Volume I, II, III, IV”. CONTENTS: CHAPTER 1. Nature of Bonding in Organic molecules: Delocalized Chemical Bonding; Conjugation; Cross Conjugation; Resonance; Hyperconjugation; Tautomerism; Aromaticity in Benzenoid and Nonbenzenoid Compounds; Alternant and Non-Alternant Hydrocarbons; Huckel’s Rule: Energy Level of p-Molecular Orbitals; Annulenes; Antiaromaticity; Homo-Aromaticity; PMO Approach; Bonds Weaker than Covalent; Addition Compounds: Crown Ether Complexes and Cryptands, Inclusion Compounds, Cyclodextrins; Catenanes and Rotaxanes CHAPTER 2. Stereochemistry: Chirality; Elements of symmetry; Molecules with more than one chiral centre: diastereomerism; Determination of relative and absolute configuration (octant rule excluded) with special reference to lactic acid, alanine & mandelic acid; Methods of resolution; Optical purity; Prochirality; Enantiotopic and diastereotopic atoms, groups and faces; Asymmetric synthesis: cram’s rule and its modifications, prelog’s rule; Conformational analysis of cycloalkanes (upto six membered rings); Decalins; Conformations of sugars; Optical activity in absence of chiral carbon (biphenyls, allenes and spiranes); Chirality due to helical shape; Geometrical isomerism in alkenes and oximes; Methods of determining the configuration CHAPTER 3. Reaction Mechanism: Structure and Reactivity: Types of mechanisms; Types of reactions; Thermodynamic and kinetic requirements; Kinetic and thermodynamic control; Hammond’s postulate; Curtin-Hammett principle; Potential energy diagrams: Transition states and intermediates; Methods of determining mechanisms; Isotope effects; Hard and soft acids and bases; Generation, structure, stability and reactivity of carbocations, carbanions, free radicals, carbenes and nitrenes; Effect of structure on reactivity; The Hammett equation and linear free energy relationship; Substituent and reaction constants; Taft equation CHAPTER 4. Carbohydrates: Types of naturally occurring sugars; Deoxy sugars; Amino sugars; Branch chain sugars; General methods of determination of structure and ring size of sugars with particular reference to maltose, lactose, sucrose, starch and cellulose. CHAPTER 5. Natural and Synthetic Dyes: Various classes of synthetic dyes including heterocyclic dyes; Interaction between dyes and fibers; Structure elucidation of indigo and Alizarin CHAPTER 6. Aliphatic Nucleophilic Substtitution: The SN2, SN1, mixed SN1 and SN2, SNi , SN1’, SN2’, SNi’ and SET mechanisms; The neighbouring group mechanisms; neighbouring group participation by p and s bonds; anchimeric assistance; Classical and nonclassical carbocations; Phenonium ions; Common carbocation rearrangements; Applications of NMR spectroscopy in the detection of carbocations; Reactivity- effects of substrate structure, attacking nucleophile, leaving group and reaction medium; Ambident nucleophiles and regioselectivity; Phase transfer catalysis. CHAPTER 7. Aliphatic Electrophilic Substitution: Bimolecular mechanisms – SE2 and SEi; The SE1 mechanism; Electrophilic substitution accompained by double bond shifts; Effect of substrates, leaving group and the solvent polarity on the reactivity CHAPTER 8. Aromatic Electrophilic Substitution: The arenium ion: mechanism, orientation and reactivity, energy profile diagrams; The ortho/para ratio, ipso attack, orientation in other ring systems; Quantitative treatment of reactivity in substrates and electrophiles; Diazonium coupling; Vilsmeir reaction; Gattermann-Koch reaction CHAPTER 9. Aromatic Nucleophilic Substitution: The ArSN1, ArSN2, Benzyne and SRN1 mechanisms; Reactivity – effect of substrate structure, leaving group and attacking nucleophile; The von Richter, Sommelet-Hauser, and Smiles rearrangements CHAPTER 10. Elimination Reactions: The E2, E1 and E1cB mechanisms; Orientation of the double bond; Reactivity –effects of substrate structures, attacking base, the leaving group and the medium; Mechanism and orientation in pyrolytic elimination CHAPTER 11. Addition to Carbon-Carbon Multiple Bonds: Mechanistic and stereochemical aspects of addition reactions involving electrophiles, nucleophiles and free radicals; Regio–and chemoselectivity: orientation and reactivity; Addition to cyclopropane ring; Hydrogenation of double and triple bonds; Hydrogenation of aromatic rings; Hydroboration; Michael reaction; Sharpless asymmetric epoxidation. CHAPTER 12. Addition to Carbon-Hetero Multiple Bonds: Mechanism of metal hydride reduction of saturated and unsaturated carbonyl compounds, acids, esters and nitriles; Addition of Grignard reagents, organozinc and organolithium; Reagents to carbonyl and unsaturated carbonyl compounds; Wittig reaction; Mechanism of condensation reactions involving enolates – Aldol, Knoevenagel, Claisen, Mannich, Benzoin, Perkin and Stobbe reactions; Hydrolysis of esters and amides; Ammonolysis of esters.

The scientific and practical interest in coronands (crown ethers), cryptands, podands as complexing agents for cations as well as for anions and neutral low molecular species is undeniable 1,2). The chemistry of crown compounds is steadily increasing. About 250 original papers dealing with crown chemistry appeared only in 1980. New molecules· with crown ether properties are constantly synthesized and new applications discov,?red. Owing to lack of space, only a small number of the original publications is men tioned here. Thus, in the literature compilation only some, but relevant works are selected for each chapter. Whenever possible, reference is made to reviews or review-like articles alone by means of which origin,al works can be consulted. The reviews given under ref. 1) are considered to be the most relevant. The formulae presented in the figures should be understood as representative structures outlining a specific field. 2 Classification of Oligo-/Multidentate Neutral Ligands and of their Complexes Today, a distinction is made between the classical ring oligoethers (crown ethers) and monocyclic coronands, oligocyclic spherical cryptands and the acyclic podands with respect to topological aspects 3). This classification and the topology are illustrated in Fig. 1, each figure representing the minimum number of donor atoms and chain segments characteristic of each class of compounds. Multidentate mono cyclic ligands with any type of donor atoms are called coronands ("crown compounds"), while the term crown ether should be reserved for cyclic oligoethers exclusively containing oxygen as donor atom.

"This volume provides a comprehensive state-of-the-art account, exclusively devoted to the analytical chemistry of Macrocyclic (crown ethers), Macrobicyclic (cryptands) and the Supramolecular compounds (calixarene and calyx(n) resorcinarene and rotaxanes). These compounds having a great deal of similarity in their chemical characteristics have direct application in biosciences, analytical chemistry, solvent extraction, chromatography, spectroscopy and ion selective electrodes."--BOOK JACKET.

The synthesis of macrocycles is an art in itself. Template-controlled synthesis provides elegant access to fascinating macrocyclic structures. Polyazamacrocycles, crown ethers, cryptands, rotaxanes, knots -- the range of macrocyclic compounds is as broad as their potential application as molecular switches, in ion exchange, electron transfer or catalysis. This book provides authoritative information on all aspects of template-controlled macrocyclizations. It covers in depth the current state of research on template processes - novel synthetic techniques and mechanistic approaches. The critical discussion of the diverse synthetic routes includes the detailed characterization of the broad variety of macrocyclic products. References to applications of macrocyclic compounds and over 1,500 citations make this handbook an indispensable tool for chemists in academia and industry. Researchers in organic and supramolecular chemistry, biotechnology, and inorganic chemistry will find inspiration for the design, synthesis, and myriad uses of new synthetic macrocycles.