THE CHEMICAL BOND

Therald Moeller , ... Clyde Metz , in Chemical science: With Inorganic Qualitative Analysis, 1980

9.eleven Coordinate covalent bonds

A single covalent bond in which both electrons in the shared pair come from the aforementioned cantlet is called a coordinate covalent bond. To indicate a coordinate covalent bond an pointer is sometimes drawn from the atom that donates the electron pair toward the atom with which the pair is shared.

The donor cantlet provides both electrons to a coordinate covalent bond and the acceptor atom accepts an electron pair for sharing in a coordinate covalent bond. For coordinate covalent bonds, as for any other kind of bail, information technology is impossible to distinguish among the electrons once the bond has formed. For example, a hydrogen ion unites with an ammonia molecule by a coordinate covalent bond to form the ammonium ion

just all four hydrogens in the ammonium ion are akin.

Read full affiliate

URL:

https://www.sciencedirect.com/scientific discipline/article/pii/B9780125033503500147

Structure and Bonding in Organic Compounds

Robert J. Ouellette , J. David Rawn , in Organic Chemistry, 2014

Covalent Bonds

Covalent bonds are much more than common in organic chemistry than ionic bonds. A covalent bond consists of the simultaneous attraction of two nuclei for ane or more than pairs of electrons. The electrons located between the ii nuclei are bonding electrons. Covalent bonds occur between identical atoms or between different atoms whose departure in electronegativity is insufficient to allow transfer of electrons to form ions.

Permit'due south consider the covalent bond in the hydrogen molecule. A hydrogen molecule forms from two hydrogen atoms, each with one electron in a 1   s orbital. The two hydrogen atoms are attracted to the same pair of electrons in the covalent bond. The bail is represented either as a pair of "dots" or every bit a solid line. Each hydrogen atom acquires a helium-like electron configuration.

H + H H •• H or H H

Energy is released when the electrons associated with the ii hydrogen atoms class a covalent bond. The process releases heat; therefore, it is exothermic. The heat released when one molecule of a chemical compound forms at 298   One thousand is the standard enthalpy changeH°) for the procedure. ΔH° for forming a mole of hydrogen from two hydrogen atoms is −   435   kJ mole−ane. Since free energy is released in the reaction, the hydrogen molecule is more than stable than the two hydrogen atoms. The reverse process, pulling the two bonded hydrogen atoms apart, requires 435   kJ mole−i, a quantity called the bond forcefulness of the H─H bond.

The two hydrogen nuclei are separated by a altitude called the bond length. This distance results from a balance between attractive and repulsive forces. There is an attraction betwixt the nuclei and the bonding electrons, merely at that place is also a repulsion between the two nuclei likewise equally between the two electrons. Effigy ane.5 is a schematic diagram of these bonny and repulsive forces. Information technology provides a starting point for our discussion of bonding.

Figure 1.5. Bonding Forces in a Hydrogen Molecule

When a covalent bail forms between two hydrogen atoms, at that place are 2 sets of electrostatic repulsions (nuclear–nuclear and electron–electron, reddish), only four sets of electrostatic attractions (green). The bonny forces are equal in magnitude, but opposite in sign. Each hydrogen nucleus attracts both electrons. The net result is that the energy of the arrangement decreases when the bail forms. This elementary electrostatic model for bonding does not adequately describe chemic bonds. For that we will need to expand our analysis, and we will do that in the following sections.

A covalent bail also occurs in Cl2. In the chlorine molecule, the two chlorine atoms are attracted to the aforementioned pair of electrons. Each chlorine atom has seven valence electrons in the tertiary energy level and requires one more electron to form an electron core with an argon electron configuration. Each chlorine atom contributes 1 electron to the bonded pair shared by the 2 atoms. The remaining six valence electrons of each chlorine atom are not involved in bonding. They are variously called nonbonding electrons, lonely pair electrons, or unshared electron pairs.

Equally we noted earlier, a covalent bond is fatigued as a dash in a Lewis structure. As well, in a Lewis structure, nonbonding electron pairs are shown as "dots." The Lewis structures of four simple organic compounds: methane, aminomethane, methanol, and chloromethane are shown beneath with both bonding and nonbonding electrons.

The hydrogen cantlet and the halogen atoms form only one covalent bail to other atoms in stable neutral compounds. However, the carbon, oxygen, and nitrogen atoms tin can bond to more than than one cantlet. The number of covalent bonds an atom can form is called the valence of the atom. The valence of a given atom is the same in virtually stable neutral organic compounds. Tabular array 1.2 lists the valences of some mutual elements contained in organic compounds.

Table 1.2. Valences of Mutual Elements one

Atom Valence
Hydrogen i
Fluorine 1
Bromine ane
Chlorine 1
Iodine 1
Oxygen ii
Sulfur 2
Nitrogen 3
Carbon 4
i
The valence is the usual number of bonds formed by the atom in neutral compounds.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780128007808000012

Review of Basic Organic Chemistry

Eric Stauffer , ... Reta Newman , in Burn Droppings Analysis, 2008

iii.ii.3 Covalent Bonds

Covalent bonds are the virtually important means of bonding in organic chemistry. The germination of a covalent bail is the consequence of atoms sharing some electrons. The bail is created by the overlapping of ii atomic orbitals [ 1]. This process is illustrated in Figure 3-4. In this type of bond, each shared electron will be counted toward both atoms' valence shells for the purpose of satisfying the octet dominion. In a single bond one pair of electrons is shared, with i electron being contributed from each of the atoms. Double bonds share 2 pairs of electrons and triple bonds share iii pairs of electrons. Bonds sharing more than i pair of electrons are called multiple covalent bonds.

FIGURE 3-4a. Ii due south orbitals form a σ bail.

Effigy 3-4b. An s orbital and a p orbital also grade a σ bail.

FIGURE 3-4c. Two p orbitals parallel to their internuclear centrality also form a σ bond.

(Source: McMurry J an Fay RC (2003) Chemistry, ivthursday edition Prentice Hall, Upper Saddle River, NJ. Reprinted with the permission o Prentice Hall, Upper Saddle River, New Jersey, Us.)

In a unmarried covalent bond, when the electrons are shared between two s orbitals, the resulting bond is a sigma (σ) bond every bit shown in Figure 3-4. Sigma bonds are the strongest covalent chemic bonds. Sigma bonds also occur when an due south and a p orbital share a pair of electrons or when two p orbitals that are parallel to the internuclear centrality share a pair of electrons (encounter Figure 3-iv). A pi (π) bond is the result of the sharing of a pair of electrons between two p orbitals that are perpendicular to the internuclear centrality (come across Effigy 3-5). In double and triple bonds, the start bail is a σ bond and the second and third ones are π bonds. Pi bonds are weaker than sigma bonds, however a double bond has the combined force of the σ and π bonds. Analogously, a triple bail has the combined strength of a σ and two π bonds. Equally an example, each of the hydrogen atoms in water (H2O) is bonded to the oxygen via a single bond (σ bond) whereas the oxygen atoms in carbon dioxide (CO2) are bound to the carbon atom via double bonds, each consisting of a σ bail and a π bail.

FIGURE three-5a. Ii p orbitals perpendicular to the internuclear axis form a π bond.

Effigy three-5b. In double bonds, the beginning bond is a σ bond and the second bail is a π bond. The diagram clearly explains why a double bond can no longer rotate on itself.

Effigy iii-5c. In triple bonds, the first bail is a σ bond and the last two bonds are π bonds.

(Source: McMurry J and Fay RC (2003) Chemical science, 4thursday edition Prentice Hall, Upper Saddle River, NJ. Reprinted with the permission of Prentice Hall, Upper Saddle River, New Bailiwick of jersey, United states of america.)

Read total chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780126639711500075

Surface modification of metal oxide nanoparticles to realize biological applications

Nisha Yadav , ... Sanjay Singh , in Reference Module in Materials Science and Materials Engineering, 2021

Covalent Binding

A covalent bond tin be represented as a linkage between electron pair and ii atoms. Different molecules such every bit hydrogen, nitrogen, chlorine, water, ammonia accept a covalent bond, and other ligands with sulfate, amide, silane, carboxyl, hydroxyl groups are covalently bound the MONPs and human action equally a linker between the biomolecules and NPs. For example, Varache et al. conjugated carboxyl groups to mesoporous SiOii NPs (covalently attached) to bind with PEG or PEI (Varache et al., 2019). Further, cisplatin was conjugated with PEG or PEI coated SiOtwo NPs and studied the drug release design after surface functionalization. The results revealed that PEI-coated SiO2 NPs were more efficient in delivering cisplatin than PEG-coated SiO2 NPs. Jaramillo et al. (2017) attempted to surface functionalized ZnO NPs with APTES using the direct mixing method, where ZnO NPs and APTES were mixed for 24 hrs nether constant stirring. The surface functionalization was confirmed using FTIR and Raman spectroscopy. The results suggested that APTES was fastened on the surface of ZnO NP via one or two Si-O-Zn (covalent bond) bonds.

Read full affiliate

URL:

https://world wide web.sciencedirect.com/science/commodity/pii/B978012822425000018X

Structure of Organic Compounds

Robert J. Ouellette , J. David Rawn , in Principles of Organic Chemistry, 2015

Covalent Bonds

A covalent bail consists of the mutual sharing of ane or more pairs of electrons betwixt two atoms. These electrons are simultaneously attracted by the two atomic nuclei. A covalent bond forms when the divergence between the electronegativities of ii atoms is as well small for an electron transfer to occur to form ions. Shared electrons located in the infinite between the two nuclei are called bonding electrons. The bonded pair is the "glue" that holds the atoms together in molecular units.

The hydrogen molecule is the simplest substance having a covalent bond. It forms from two hydrogen atoms, each with i electron in a 1s orbital. Both hydrogen atoms share the two electrons in the covalent bond, and each acquires a helium-similar electron configuration.

H + H H H

A similar bond forms in Cl2. The two chlorine atoms in the chlorine molecule are joined by a shared pair of electrons. Each chlorine cantlet has seven valence electrons in the third energy level and requires one more electron to form an argon-like electron configuration. Each chlorine atom contributes i electron to the bonding pair shared past the two atoms. The remaining 6 valence electrons of each chlorine cantlet are not involved in bonding and are concentrated effectually their corresponding atoms. These valence electrons, customarily shown as pairs of electrons, are variously called nonbonding electrons, lone pair electrons, or unshared electron pairs.

The covalent bail is fatigued every bit a nuance in a Lewis construction to distinguish the bonding pair from the alone pair electrons. Lewis structures show the nonbonding electrons equally pairs of dots located most the atomic symbols for the atoms. The Lewis structures of four simple organic compounds—methane, methylamine, methanol, and chloromethane—are drawn hither to show both bonding and nonbonding electrons. In these compounds carbon, nitrogen, oxygen, and chlorine atoms have 4, three, two, and one bonds, respectively.

The hydrogen cantlet and the element of group vii atoms course just one covalent bond to other atoms in most stable neutral compounds. Even so, the carbon, oxygen, and nitrogen atoms can simultaneously bond to more ane atom. The number of such bonds is the valence of the atom. The valences of carbon, nitrogen, and oxygen are four, 3, and two, respectively.

Read total affiliate

URL:

https://www.sciencedirect.com/science/commodity/pii/B978012802444700001X

Ionic Bonding, Crystals, and Intermolecular Forces

James Eastward. House , Kathleen A. House , in Descriptive Inorganic Chemical science (3rd Edition), 2016

4.2.1 Dipole–Dipole Forces

Covalent bonds can have appreciable polarity due to the unequal sharing of electrons by atoms that have dissimilar electronegativities. For near types of bonds, this charge separation amounts to just a modest percentage of an electron charge. For example, in Hi it is about v%, but in HF where the departure in electronegativity is almost one.8 units, it is about 44%.

In lodge to show how dipole–dipole forces ascend, let united states consider a polar molecule that can be represented every bit

where δ+ and δ− correspond the fraction of an electronic accuse residing on the positive and negative ends, respectively. When polar molecules are allowed to arroyo each other, in that location will exist an electrostatic interaction between them. The actual energy of the interaction will depend on the orientation of the dipoles with respect to each other. 2 limiting cases can be visualized as shown in Figure 4.9.

Figure 4.9. Interaction of dipoles by the (a) parallel and (b) antiparallel modes.

By assuming an averaging of all possible orientations, the energy of interaction, Due east D can be shown to be

(4.13) East D = two μ iv iii k T R half-dozen

where μ is the dipole moment, R is the average distance of separation, k is Boltzmann'south abiding, and T is the temperature (K). On the basis of this interaction, it is expected that polar molecules should associate to some extent, either in the vapor country or in solvents of low dielectric constant. Dipole clan in a solvent having a low dielectric abiding leads to an abnormal human relationship between the dielectric abiding of the solution and the concentration of the polar species. Although the procedure will not exist shown, it is possible to calculate the association constants for such systems from the dielectric constants of the solutions. If the solvent has a high dielectric constant and is polar, information technology may solvate the polar solute dipoles thus preventing association which forms aggregates. Consequently, the association constants for polar species in solution are e'er dependent on the solvent used.

Read full chapter

URL:

https://www.sciencedirect.com/scientific discipline/article/pii/B978012804697500004X

Basic Coordination Chemistry

Vasishta Bhatt , in Essentials of Coordination Chemistry, 2016

1 Introduction

The coordination compounds establish their applications long earlier the institution of coordination chemistry. Bright blood-red coloured alizarin dyes were nether applications even before the fifteenth century. This bright red dye, now characterized as a chelated complex of hydroxyanthraquinone with calcium and aluminium metal ions, is shown in Effigy 1.

Figure 1. Structure of alizarin dye.

Subsequently, in the sixteenth century, the formation of a well-known fellow member of today's coordination chemistry family unit, the tetraamminecupric ion [Cu(NH3)4]+2, was recorded upon contact between contumely alloy and ammonium chloride. Add-on of Prussian blueish Feiv[Fe(CN)6]three·xH2O increased the utilise of coordination compounds in dyes and pigments. A platinum complex Thousand2[PtCl6] offered an application for the refinement of platinum metal. Thus, before the coordination chemical science was structured, the coordination compounds, complexes and chelates found their applications.

A systematic investigation of construction and bonding in coordination chemical science began with the inquisitiveness of Tassaert (1798), which was extended by distinguished chemists like Wilhelm Blomstrand, Jorgensen and Alfred Werner [1] until the end of the nineteenth century. In the events, Werner's coordination theory (1893) became the base of the modernistic coordination chemistry. It is worth noting that the electron was discovered subsequent to Werner's theory.

The bonding in compounds like CoCliii and NH3 were hands understood and explained and hence such compounds were regarded every bit elementary compounds. For instance, the +3 formal oxidation of cobalt in cobalt chloride is balanced past 3 uni-negative chloride ions and the coexistence of these ionic moieties to grade a molecule is understood and explained. Similarly, the valence beat (n  =   2) of nitrogen (N   =   7) contains five electrons and 4 orbitals (2s, 2p x , 2p y and 2p z ). Keeping an electron pair in 1 of these orbitals while the other 3 remains half filled, an opportunity for three hydrogen atoms to contribute i electron each for the formation of a covalent bond with nitrogen, can too be explained. Thus an ammonia molecule has 3 North single bondH covalent bonds and ane lone pair of electrons over the nitrogen cantlet. It is worth noticing hither that all the valencies of all the atoms in both the molecules are fully satisfied and hence in that location is no further telescopic of bonding.

A 'circuitous' situation arises when one comes to know that the molecule CoCl3 can encompass six ammonia molecules, resulting into a tertiary contained entity. This situation was fully understood and explained by Werner's coordination theory, followed past naming the entity as 'complex'.

ane.one Definitions

Coordination compounds are the compounds containing one or more than coordinate covalent bonds.

Coordinate covalent bonds are the covalent bonds in which both the bonding electrons are contributed by one of the bail partners. Figure 2 distinguishes the covalent bonds from the coordinate covalent bond in NHthreeBFiii. While the 3 Bsingle bondF covalent bonds are formed due to the sharing of electron pairs resulting from contributions of both boron and fluorine atoms, an Nsingle bondB bond is formed due to the donation of a lonely pair of electrons from nitrogen into the empty orbitals of boron. The coordinate covalent bail is shown by an arrow with its caput pointing towards the direction of the donation of an electron pair, as shown in Effigy 2.

Figure two. Bonding in NHthreeBF3.

A complex is a molecule/ion containing a central metallic atom/ion surrounded by a definite number of ligands held by secondary valences or coordinate covalent bonds.

Primary valency refers to the charge over the metallic ion east.thousand. Co(Three) has +3 charge, which tin can be balanced by −iii charge-forming compounds like CoCl3. The primary valency is ionic and is satisfied in the 2d coordination sphere, as shown in Figure 3.

Effigy 3. First and second coordination spheres in [Co(NH3)6]Cl3.

Secondary valency is the number of empty valence orbitals, as illustrated for [Co(NH3)vi]Cl3 in the figure. The Co(III) ion has six empty valence orbitals. Hence its secondary valency is six. Secondary valency is a coordinate covalent valency, and it is satisfied in the kickoff coordination sphere of the metal ion, equally shown in Figure 4.

Figure 4. Secondary valency of Co(III) in [Co(NH3)6]Cl3.

Coordination number is a property of the metal ion representing the total number of donor atoms direct attached to the central cantlet. In the higher up case, the coordination number of Co(3) is six, as six nitrogen donor atoms are direct connected to the central metal ion (cobalt(III)).

Ligand is whatsoever cantlet, ion or neutral molecule capable of donating an electron pair and bonded to the cardinal metal ion or atom through secondary valency.

Dentate character is a property of a ligand representing a number of analogous atoms.

In the case of [Co(NHiii)6]Cl3, ammonia, NH3 the ligand contains i donor cantlet (N). Hence its dentate character is one and is classified equally a monodentate ligand. Similarly, chloro (Cl) is an anionic, monoatomic and monodentate ligand, while hydroxo (OH) is a diatomic, monodentate and anionic ligand. Aquo (OHii) represents a neutral triatomic monodentate ligand. A few pop ligands and their characteristics are shown in Effigy 5.

Figure 5. Structures and characteristics of a few important ligands.

Due to a college dentate character of ligands, a diversity of complexes known as chelate is as well formed sometimes. Chelate is a chemical compound formed when a polydentate ligand uses more than than one of its coordinating atoms to form a airtight-ring structure, which includes the key metal ion. Five- and half dozen-membered rings are known to provide extra stability to the chelates. The process of chelate formation is known as chelation. A polydentate ligand involved in chelate germination is also known as a chelating ligand. Chelates generally exhibit higher stability than coordinating complexes.

A polydentate ligand may exist attached to the cardinal metal ion through more than i kind of functional grouping. The number and kind of linkages past which the metallic ion is attached with the ligands can thus become a benchmark for the classification of chelates. The covalent bonds are formed by the replacement of one or more than H-atoms, while coordinate covalent bonds are formed by the donation of an electron pair from the ligands. Some of the chelates involving a multifariousness of polydentate ligands and linkages are shown in Figure vi. The coordinate covalent linkages are shown by thin, thread-similar bonds.

Effigy 6. Structures and characteristics of a few chelates.

Polynuclear complex is a complex with more than i metal cantlet/ion. These metal ions are sometimes bridged through appropriate ligands, resulting into the formation of a bridged polynuclear complex.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B978012803895600001X

Introduction

Huangxian Ju , ... Feng Yan , in Immunosensing for Detection of Poly peptide Biomarkers, 2017

ane.3.3 Covalent binding

Covalent bonds are generally formed between side-chain-exposed functional groups of proteins and suitably modified transducer surface, resulting in an irreversible binding and producing a high surface coverage [ 71,72]. One of the nigh unremarkably used methods for covalent immobilization is to couple the antibody randomly via their free amino groups to an activated sensor surface (Fig. 1.5). Chemic coupling agents, such every bit carbodiimides and succinimidyl esters, may be used to actuate carboxylic acids on sensor surfaces. Amines or alcohols can be activated by isothiocyanates, epoxides, glutaraldehyde (GA), or other aldehydes. Oxidation of alcohols is achieved with periodate to yield aldehydes, which react readily with amines. In addition, conversion of alcohols to a highly reactive ester by cyanogen bromide allows for further reaction with amines of antibody. For example, the ultrasonication treatment of carbon nanotubes (CNTs) in full-bodied acid condition can produce abundant carboxyl groups on their surface. When CNTs are modified on the electrode surface, the carbodiimide/Due north-hydroxysuccinmide system is commonly applied to link antibodies with the activated carboxyl groups [60].

Fig. 1.5. Schematic illustration of covalent immobilization of antibodies to sensor surfaces via their gratis amino groups. Reaction (a) involves activation of carboxylic acids (COOH), achieved with carbodiimides and succinimyl esters. Reaction (b) shows amine surfaces (NH2), which can be activated using isothiocyanates, epoxides, or aldehydes. Reaction (c) shows alcohol surfaces that tin can be activated using periodate oxidation, isothiocyanates, epoxides, aldehydes, and cyanogen bromide.

Another approach is to use bifunctional cross-linking reagents [73]. The cross-linking reagents comprise two unlike reactive groups, thereby providing a means of covalently linking 2 dissimilar target groups on the sensor surface and protein biomolecules. A broad variety of these linkers such as (three-aminopropyl)triethoxysilane (APTES) [74], (3-glycidoxypropyl)-trimethoxysilane (GPTMS) [75], 3-mercaptopropyltrimethoxysilane (MPTMS) [76], diazonium cation [77], and various thiol derivatives [78–80] are commercially available to cover a wide range of functional groups necessary. For instance, the silanization reaction of APTES at the hydroxyl group-containing substrate (east.yard., drinking glass, electrode, and microwell plate) can provide amino groups at the surface. Then antibodies can be coupled to the substrate via the cantankerous-linking of GA (Fig. ane.6).

Fig. one.six. Schematic analogy of immobilization of antibiotic by the bifunctional cantankerous-linking reagents of APTES and GA.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780081019993000013

CRYSTAL Structure OF THE METALLIC ELEMENTS

W. STEURER , in Physical Metallurgy (Fourth Edition), 1996

two.ane.1. The covalent bail

The covalent bond may be described in terms of the more qualitative VB (valence bond) theory by overlapping diminutive orbitals occupied by unpaired valence electrons ( fig. 1). Its strength depends on the degree of overlapping and is given by the exchange integral. In terms of the more quantitative LCAO–MO (linear combination of atomic orbitals – molecular orbitals) theory, molecular orbitals are constructed past linear combination of diminutive orbitals (fig. 2). The resulting bonding, non-bonding and anti-bonding molecular orbitals, filled up with valence electrons co-ordinate to the Pauli exclusion principle, are localized betwixt the bonding atoms with well defined geometry. Generally, covalent bonds can be characterized as strong, directional bonds. Increasing the number of atoms contributing to the bonds increases the number of molecular orbitals and their energy differences become smaller and smaller. Finally, the discrete energy levels of the molecular orbitals condense to quasicontinuous bands separated past energy gaps. Since in a covalent bond each cantlet reaches its particular stable noble gas configuration (filled beat out) the energy bands are either completely filled or empty. Owing to the localization of the electrons, it needs much energy to lift them from the last filled valence band into the empty conduction ring. The archetype example of a crystal congenital from only covalently bonded atoms is diamond: all carbon atoms are bonded via tetrahedrally directed sp3 hybrid orbitals (fig. 3). Thus the crystal structure of diamond results as a framework of tetrahedrally coordinated carbon atoms (fig. four).

Fig. 1. Schematic structure of the atomic s-, p- and d-orbitals

(from Vainshtein et al. [1982]).

Fig. ii. (a) Bonding and (b) anti-bonding molecular orbitals of the H2 molecule, (c) Schematic cartoon of the building of the most important molecular orbitals from atomic orbitals and (d), (e) examples of molecular orbitals (bonding: σ, π and anti-bonding σ*, π*)

(from Vainshtein et al. [1982]).

Fig. iii. Hybridization of (a) one s- and three p-orbitals to (b) sp3–hybrid orbitals (c) which are directed along tetrahedron axes

(from Vainshtein et al. [1982]).

Fig. iv. The structure of diamond cF8–C, space group Fd 3 ¯ m, No. 227, 8a: 0 0 0, ¾ ¼ ¾. All carbon atoms are tetrahedrally coordinated, they occupy the positions of a face up-centered cubic lattice and 1 half of the centers of the 8th cubes.

Read full chapter

URL:

https://www.sciencedirect.com/science/commodity/pii/B9780444898753500053

Supramolecular Receptors

J. Gawroński , ... U. Rychlewska , in Comprehensive Supramolecular Chemistry 2, 2017

Abstract

Dynamic covalent bail germination between master amines and aldehydes is the basis of synthesis of macrocyclic imines under thermodynamic equilibrium weather condition. With the use of chiral vicinal diamines and aromatic di- or trialdehydes, a variety of chiral imine macrocycles or cages can be readily obtained with high yields. The imine macrocycles are rigid, while the imine reduction products, oligoamines, are flexible. Triangular [iii  +   three] cyclocondensation–reduction products are versatile chiral hexaamines with numerous applications for chiral discrimination in NMR spectroscopy and for asymmetrical catalysis. These and related aza-macrocycles display tendency toward formation of supramolecular complexes.

Read full chapter

URL:

https://world wide web.sciencedirect.com/scientific discipline/article/pii/B9780124095472125211