This chapter focuses on the wide variety of species that are classified as acids and bases. It first explains the Brønsted -definition, in which an acid is a proton donor and a base is a proton acceptor. The discussion on the characteristics of Brønsted acids covers the periodic trends in aqua acid strength, simple oxoacids, anhydrous oxides, and polyoxo compound formation. The chapter also introduces the Lewis definition of acids and bases which deals with reactions involving electron-pair sharing between a donor (the base) and an acceptor (the acid). This broadening enables the extension of the discussion on acids and bases to include species that do not contain protons and reactions in nonprotic media. Furthermore, the chapter introduces a molecular orbital description of hydrogen bonding. Lastly, it discusses the nonaqueous solvents and -describes some of the most important applications of acid–base chemistry.
Chapter
Acids and bases
Chapter
Acids and bases
This chapter focuses on acids and bases. The broadest definition of acids and bases is the Lewis definition. In this scheme, a Lewis acid is an electron-pair acceptor while a Lewis base is an electron-pair donor. Meanwhile, the Brønsted–Lowry concept is probably the second most commonly employed description of acids and bases, although in aqueous solution it is by far the most widely used. In this scheme, an acid is defined as a proton donor and a base as a proton acceptor. It is important to note that the concept of Lewis acidity and basicity incorporates the Brønsted–Lowry approach as a special case. The chapter then looks at element oxides and hydroxides, as well as the Lewis acidity of the heavier p-block elements. It also considers hard and soft acids and bases.
Chapter
Acids and bases to Aufbar principle
This chapter discusses acids and bases and the Aufbau principle. In the Brønsted definition, acids and bases function as proton donors and acceptors in a complementary manner. Compounds which are able to function both as Brønsted acids and bases are described as amphoteric. G.N. Lewis defined acids and bases in terms of electron-pair donation and acceptance. A base in an electron-pair donor and acid is an electron-pair acceptor. The chapter then looks at Lewis basicity trends, before considering actinides, alkali metals and alkaline earth metals, allotropy, the alternation effect, amorphous solids and anhydrous compounds, and aprotic solvent. The Aufbau principle states that the lowest energy (most stable) orbitals are occupied first and in a manner consistent with the Pauli exclusion principle, i.e. with two electrons with opposite spins in each singly degenerate orbital.
Chapter
Activation of ligands
This chapter analyses the general reactivity of the ligand, which defines elementary reactions in catalysis that involve metal sites and action of metalloenzymes at the atomic level. It looks at factors controlling the attack of hydroxide at organic carbonyl compounds which are of direct relevance to the action of the zinc-containing enzymes carboxypeptidase and carbonic anhydrase. It also mentions the factors that favour the protonation and reduction of coordinated dinitrogen, which are important to the understanding of the action of the nitrogenases. The chapter considers the interaction between a metal and a ligand that reveal several types of bonding. It outlines how the ligand is more susceptible to attack by nucleophiles and bonds within the ligand that may be prone to cleavage.
Chapter
Activity effects
This chapter addresses activity effects. The experimental evidence from almost a century of precise measurements of equilibrium constants shows that, in dilute solutions, they are essentially constant only when compared at constant ionic strength. By excluding the contributions from uncharged species, the ionic strength clearly reflects coulombic interactions. It is important to realize where activity corrections apply, and where they do not. Since interionic attractions can lower the energetics of ions, they can affect the numerical values of the equilibrium constants. However, activity effects have no direct influence on the mass and charge balance equations. Similarly, activity effects do not change the equivalence volume in a titration, but can change the shape of the titration curve. The chapter then looks at ionic interactions and non-ionic interactions.
Chapter
Agostic interactions to angular overlap model
This chapter begins by discussing agostic interactions, which formally increase the total valence electron count by two and may be viewed as a means of making the electron deficient molecule conform more closely to the Effective Atomic Number Rule. The interaction has approximately the same strength as a hydrogen bond. The occurrence of agostic interactions may be demonstrated unambiguously by neutron diffraction studies or circumstantial evidence may be accumulated from spectroscopic data. The chapter then looks at the angular overlap model, which is based on a very approximate form of molecular orbital theory. It is useful for accounting for the geometries of transition metal complexes and the relative positions of ligands in the spectrochemical series.
Chapter
The alkaline and alkaline earth metals
This chapter focuses on Alkaline metal ions (sodium and potassium ions) and alkaline earth metal ions (magnesium and calcium ions), which play important roles in a plethora of physiological processes. It discusses the mechanisms that are responsible for steering and control of the ion concentrations in the extracellular space and the cytosolic cell compartments. It describes the four main transportation routes for alkaline and alkaline earth metal ions and tackles ion channels — the membrane-bound proteins which are gated by chemical, mechanical, electric, or light stimuli. The chapter also explains the concept of exchange kinetics. Furthermore, it looks at the biomineralization of calcium with special reference to its impact on the stabilization of bone structures through the formation of hydroxyapatite.
Chapter
Amides
This chapter discusses enamines. It explains the process of achieving enamine through regaining neutrality by losing a proton adjacent to the iminium moiety. Additionally, these compounds rarely serve as nucleophiles or bases on nitrogen. The chapter discusses the formation of enamines from amine and aldehyde or ketone. It highlights how electrophiles are required to be quite reactive as enamines are moderately nucleophilic. The chapter adds the hydrolysis of enamine which is an effort to regenerate the original secondary amine and reveal the carbonyl group. Also, it explores the tautomerism of using imines as enamines and vice versa.
Chapter
Amines
This chapter introduces the features of nitrogen. It recognises nitrogen as the most abundantly gas in the world despite its lack of reactivity. Next, the chapter highlights the flexible organic compounds which can be combined with the presence of nitrogen. It looks into neutral nitrogen, trivalent nitrogen, and common organonitrogen functional groups. The chapter also discusses the components of saturated nitrogen compounds. It highlights the importance of nitrogen in organic chemistry and the significance of organonitrogen chemistry in the evolution of life. In terms of modern life, organonitrogen chemistry is linked to natural products such as DNA, peptides, proteins, alkaloids, man-made pharmaceuticals, fibres, and dyes.
Chapter
Ammonium compounds
This chapter focuses on amines. Saturated amines are regarded as the simplest organonitrogen compound. The chapter highlights the importance of amines as they occur widely in nature and are used often as building blocks for more complex compounds and co-reagents in numerous organic reactions. The chapter notes nitrogen acting as nucleophile or base to facilitate the reactions on the nitrogen lone pair. Additionally, the chapter discusses the interplay between nucleophilicity and basicity alongside the reactions of amines. It concludes amines as bases that are readily protonated. Next, amines are also powerful nucleophiles following their reactivity with alkyl halides, carboxylic acid derivatives, aldehydes, ketones, and nitrous acid.
Chapter
Appendix I
Answers to exercises
Chapter 1
(a) D3h, (b) C4v, (c) C3v, (d) C2h, (e) D6h, (f) C2v, (g) C2v? (h) D3h, (i) C3v, (j) D5h...
Chapter
Appendix II
Character tables for selected point groups
C
E
C = 2
A
1
1
, R, , ,
B
1
–1
x, R, R
Chapter
Applications
This chapter assesses the many potential applications of the f-elements and their compounds. By volume, the main applications of the rare earths are in metallurgy and alloys, and in permanent magnets. The unique optical and magnetic properties of the lanthanoids are key to many of the applications of these elements. For example, Eu and Tb are used as phosphors in fluorescent lighting, and the Nd:YAG laser is the most widely used IR laser. Complexes of Gd are used as contrast agents in MRI imaging. There is a constant challenge in rare earth technology to find uses for the more abundant elements (La and Ce) that are inevitably produced alongside elements such as Nd that are in high demand but available in lower abundance. Meanwhile, the use of U in nuclear reactors is the main application of the actinoids. However, there are also smaller-scale applications based on their radiochemical properties.
Book
Robert de Levie
Aqueous Acid-Base Equilibria and Titrations uses new theoretical developments which have led to more generalized approaches to equilibrium problems; these approaches are often simpler than the approximations which they replace. Acid-base problems are readily addressed in terms of the proton condition, a convenient amalgam of the mass and charge constraints of the chemical system considered. The graphical approach of Bjerrum, Hȩgg, and Sillén is used to illustrate the orders of magnitude of the concentrations of the various species involved in chemical equilibria. Based on these concentrations, the proton condition can usually be simplified, often leading directly to the value of the pH. In the description of acid-base titrations, a general master equation is developed. The text provides a continuous and complete description of the entire titration curve, which can then be used for computer-based comparison with experimental data. Graphical estimates of the steepness of titration curves are also developed, from which the practicality of a given titration can be anticipated. Activity effects are described in detail, including their effect on titration curves. The discussion emphasizes the distinction between equilibrium constants and electrometric pH measurements, which are subject to activity corrections, and balance equations and spectroscopic pH measurements, which are not. Finally, an entire chapter is devoted to what the pH meter measures, and to the experimental and theoretical uncertainties involved.
Chapter
Aqueous solution species
This chapter focuses on two particular aspects of the chemistry of the second and third row d-block metals in aqueous solution: species present in solution and redox behaviour. It explores the increase in electron withdrawing power of the metal centre which is associated with an increase in oxidation state and is reflected in the fact that the hexaaqua ion of vanadium does not exist in a solution. It also discusses the loss of protons through the polarization of O-H bonds in coordinated water. This leads to the formation of hydroxo ligands and the concomitant generation of dinuclear species. The chapter describes the dramatic effect that the change in ligand has on the relative case of iron(III) reduction. It mentions the use of potential diagrams as a valuable method of displaying the redox behaviour of different species containing a particular element.
Chapter
Atomic structure
This chapter provides foundations for an explanation of the trends in the physical and chemical properties of all inorganic compounds. The chapter begins with a discussion on the origin of matter in the solar system and then considers the development of understanding of atomic structure and the behaviour of electrons in atoms. It reviews the structures and properties of atoms, acknowledging that these are crucial in understanding the behaviour of molecules and solids. The chapter also qualitatively introduces quantum theory and uses the results to rationalize properties such as atomic radii, ionization energy, electron affinity, and electronegativity.
Chapter
Atomic structure
This chapter examines the atomic structure. The concept of atoms dates back over 2000 years, while modern concepts of atomic theory date back 250 years. The simplest model for atomic structure based on Ernest Rutherford's conclusions is the Bohr model, a model put forward by the Danish physicist Niels Bohr in 1913. The Bohr model of atomic structure consists of electrons (negatively charged) revolving around the nucleus (positively charged) at certain (quantized) fixed distances in a set of orbits. Erwin Schrödinger then emphasized the wave nature of electrons using wave mechanics. The wave equation solutions for electrons in atoms require the quantum numbers n (principal quantum number), l (azimuthal or angular momentum quantum number), and ml
(magnetic quantum number). A fourth quantum number, ms
, describes spin. The chapter then looks at the electronic structure and the periodic table.
Chapter
Atomic structure
Matthew Almond, Mark Spillman, and Elizabeth Page
Edited by Elizabeth Page
This chapter discusses topics which are related to atomic structure, starting with electromagnetic waves and matter. Chemists frequently make use of spectroscopic techniques to study materials. Such techniques rely on the interaction between electromagnetic waves and matter. As well as its speed, an electromagnetic wave is also described by its wavelength and its frequency. For mostly historical reasons, spectroscopists also frequently make use of another related quantity known as the wavenumber. The chapter then considers Albert Einstein's explanation of the photoelectric effect, which is observed when electromagnetic radiation of a sufficiently high energy strikes a metal surface. It also looks at hydrogenic emission spectra and the Rydberg equation; quantum numbers and atomic orbitals; and multi-electron atoms and the periodic table.
Chapter
Atomic structure and the form of the periodic table
This chapter provides an overview of ideas on atomic structure which lead to an understanding of why the periodic table has the form that it does. The periodic table was initially constructed based on a consideration of atomic weight (nowadays referred to as relative atomic mass) and periodic trends in the chemical behaviour of the elements. It was therefore arrived at empirically, and only later were the underlying reasons for its structure understood with the development of quantum theory in the early twentieth century. The chapter then looks at the Schrödinger wave equation, which is used to describe the behaviour or properties of electrons in atoms. It also considers wavefunctions for the hydrogen atom; the energies of orbitals; and polyelectronic atoms. Ultimately, the chapter explains some of the key features of the periodic table, particularly in terms of the relative positions of the s-, p-, and d-blocks.
Chapter
Back donation to Born-Haber cycle
This chapter begins by examining back donation, base metal, bond energies, and bond order. The bond dissociation energy for a diatomic covalent molecule is the change in internal energy, where the parent molecule and product atoms are in their ground electronic states. For polyatomic molecules, there is more than one bond dissociation energy and one must be careful to specify exactly the dissociation process being referred to. Meanwhile, bond order is a prediction from theoretical considerations of the relative strength of a bond. The chapter then explains the Born–Haber cycle, a cycle of reactions based on the first law of thermodynamics, or Hess’s law, which is used to calculate the lattice energy of an ionic compound.
