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
Amines
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.
Book
Jon McCleverty
Chemistry of the First Row Transition Metals introduces this field of chemistry. The reactivity and structural properties of first-row transition metals and their compounds depend on the electronic configuration of the d electrons of the metal. The book describes the most significant structures, reactions, and other important properties of co-ordination, organometallic and solid-state compounds, and also sketches the role of first-row transition metals in biology.
Chapter
Saturated heterocycles and stereoelectronics
This chapter focuses on saturated heterocycles and stereoelectronics. What are the ‘special chemical features’ of saturated heterocycles? Putting a heteroatom into a ring does two important things. Firstly, the heteroatom makes the ring easy to make by a ring-closing reaction, or (in some cases) easy to break by a ring-opening reaction. Secondly, the ring fixes the orientation of the heteroatom—and, in particular, the orientation of its lone pairs—relative to the atoms around it. This has consequences for the reactivity and conformation of the heterocycle which can be explained using the concept of stereoelectronics. The chapter then considers the reactions and conformation of saturated heterocycles.
Chapter
Organic chemistry 1: functional groups
This chapter studies functional groups, which can be classified according to the number of bonds a given carbon has to elements of greater electronegativity. The functional group level is the number of these bonds. Reactions can be classified according to the change in functional group level. The outcome of a reaction can be rationalized by considering where the highest energy electrons are to be found, and what low energy vacant molecular orbitals are available. Within a particular functional group level, there is often a general order of reactivity for different functional groups. Ultimately, transformations from one functional group to another may take place via different mechanisms depending on the particular reagents and reaction conditions.
Book
Nathan Lawrence, Jay Wadhawan, and Richard Compton
Foundations of Physical Chemistry presents a grounding in the field of physical chemistry. The early chapters cover the structure of atoms, ions and molecules, reactivity, kinetics, and equilibria. The final chapter gives an insight into more advanced areas, drawing on real-world examples.
Chapter
Selectivity I: Chemoselectivity and protecting groups
This chapter evaluates chemoselectivity and protecting groups. In a chemoselective reaction, one functional group within the molecule reacts, leaving further potentially reactive functionality unaffected. Many of the principal transformations involved in functional group interconversions (FGIs) were introduced in the third chapter of this text. The reactions may involve addition, substitution, elimination, reduction, and oxidation. There are now a plethora of mild and selective reagents available to effect specific transformations. As a general rule, when there are two functional groups of unequal reactivity within a molecule, the more reactive can be made to react alone. However, it may not be possible to react the less reactive functional group selectively.
Book
Jeremy Robertson
Protecting Group Chemistry provides an overview of the general methods that are used to block the reactivity ofi.e. protectspecific functional groups, thus allowing others, present within the same molecule, to be manipulated unambiguously. An introductory chapter outlines protecting group strategy, relevant aspects of functional group reactivity, temporary protection, and introduces the concept of protecting group devices as an aid to unifying the wide range of available methods. The rest of the book is divided on the basis of broad classes of the experimental conditions that lead to cleavage of each protecting group (acid/electrophile, base/nucleophile, oxidising or reducing agent).
Chapter
Reactivity of macrocyclic complexes
This chapter assesses the reactivity of macrocyclic complexes. It looks at axial substitution reactions and reactions of the coordinated macrocyclic ligand. The chapter also considers demetallation and metal exchange reactions, as well as metal-centred oxidation and reduction reactions. Finally, the chapter covers ligand-centred redox processes. Numerous examples are known in which macrocyclic ligands undergo this type of redox process. Direct hydrogenation reactions of both free ligands and metal complexes are possible, although reactions of the free ligands are perhaps more common. Oxidation of a coordinated macrocyclic ligand is also a more commonly observed process, and it is convenient to distinguish between oxidation processes which involve the addition of oxygen atoms and those which involve the loss of hydrogen atoms.
Chapter
Effects on reactivity
This chapter evaluates the effects on reactivity. When two independent molecules collide in solution or in the gas phase, there is in principle no geometrical restriction on interactions between their orbitals, apart from any imposed by their intrinsic symmetries. Through-space interactions between two orbitals on the same molecule, on the other hand, are subject to the geometric constraints imposed by its structure. In the trivial case, we do not expect two groups to react with each other if they are on opposite faces of a rigid ring-system because the molecular geometry keeps them apart. Even when the groups concerned can get close, apparently within easy bond-forming distance, stereoelectronic effects may effectively prohibit reaction. Through-bond interactions also lead to many important reactions; these interactions are very clearly under stereoelectronic control.
Chapter
Radical reactions
This chapter explores radical reactions. Stereoelectronic effects on radical reaction arise from geometrical preferences for optimal orbital-orbital interactions, in the same way as the effects on ionic reactions discussed in the previous chapters. The geometries of the relevant orbital-orbital interactions are the same as in the corresponding ionic reactions because the orbitals involved are the same. What is different is that the interacting orbitals contain an odd number of electrons. Meanwhile, stereoelectronic effects on reactivity are generally simpler than for ionic reactions because the reactions are simpler. The chapter then looks at the stability of radicals and reactivity, before examining intramolecular reactions and reactions involving diradicals.
Chapter
The effect of surface structure on reactivity
This chapter discusses the effect of the surface structure on reactivity. Since the nature of the surface involved in heterogeneous catalysis is crucial to performance, it is important to consider the structure as a starting point for the discussion of catalytic properties. Generally speaking, surfaces with lower coordination surface atoms have the highest surface free energy, the highest reactivity for adsorption, and the strongest binding for the adsorbate (high adsorption heat). Because the surface is a region of high energy, thermodynamics dictates that there will be a tendency to minimise this energy. In nature, this occurs in several ways, including surface relaxation, surface reconstruction, sintering, and adsorption. The chapter then considers the surface structure of catalysts, as well as the structure dependence and independence of catalytic reactions. The best evidence for the influence of structure on a reaction comes from studies using model catalysts, namely single crystals.
Chapter
Changing the reactivity of catalytic surfaces
This chapter examines the process of changing the reactivity of catalytic surfaces. If we consider any particular reaction then, in principle, it is possible to manipulate the properties of a catalyst for that reaction by any process that alters the properties of its surface. The chapter then looks at the effects of engineering the active phase of the material by placing additives at the surface. In practice, most industrial processes have additives that act as modifiers to the chemistry at the surface. Promoters can be classed as substances which, when added to a catalyst as a minor component, improve one or more of the properties of the material with respect to product formation. Meanwhile, poisons tend to be electronegative elements. At the simplest level, they block sites on the surface and so reduce the total number of centres of activity. The chapter then discusses the process of alloying.
Book
Elaine M. McCash
Surface Chemistry conveys the fundamental concepts of surface chemistry. It describes solid surfaces, their properties at macroscopic and microscopic levels and their interrelation, and reflects the striking advances made in recent years through the study of well-defined single crystal surfaces. It begins with a discussion of the clean surface, its electronic and structural properties and goes on to describe adsorption, desorption, reactions, and reactivity at the surface. In the final section, the growth and properties of ultrathin films is introduced. Starting with the established concepts in terms of kinetics and thermodynamics, the book develops to look at phenomena such as surface dynamics and photochemistry. Important techniques which are applied to surfaces are also covered; this is a concept-driven rather than technique-driven approach.
Chapter
Selectivity III: Stereoselectivity
This chapter assesses stereoselectivity. The biological and physical properties of organic molecules used as drugs, insecticides, plant growth regulators, perfumes, etc., depend to a large extent on the stereochemistry of substituents and functional groups. Stereochemistry also has an important effect on the reactivity of compounds. In a stereoselective reaction, one stereoisomer of a mixture is produced (or destroyed) more rapidly than another, resulting in the formation of a preponderance of the favoured stereoisomer. Stereoisomers have the same carbon framework and the substituents have identical regiochemistry; however, the isomers differ in their three-dimensional spatial arrangement of atoms within the molecule. Stereoisomers containing two or more stereogenic centres are described as being diastereomers (or disastereoisomers). The chapter also looks at stereospecific reactions.
Book
A.J Kirby
Stereoelectronic Effects provides an introduction to this important topic in the study of chemistry. Stereoelectronic effects control the way molecules are put together and especially for the 'rules of engagement' which operate when they meet and react. Understanding them can give us a 'feel' or intuition for what molecules are and what they are capable of. The treatment in this text is deliberately non-mathematical and this unifying treatment shows how to build up a powerful but simple way of thinking about chemistry. Chapters examine the electronic basis of stereoelectronic effects and the effects on conformation and on reactivity. The text also considers substitutions at saturated centres. It also looks at additions and eliminations, rearrangements and fragmentations, and radical reactions.
Book
Thermodynamics of Chemical Processes describes the basic principles which govern reactivity and phase equilibria in chemical systems and contains a number of worked examples and problems. The first chapter considers preamble energy in chemical systems. The second chapter covers enthalpy and thermochemistry. The next chapter is about entropy in chemistry. There follows a chapter on free energy and equilibrium. The last chapter is about phase changes and solutions.
Chapter
Organometallic Compounds of Main Group Elements
This chapter discusses the main group of organometallic compounds which contain metal–carbon σ-bonds generated by orbital overlap along the M–C axis. It reviews the possibility of interaction of the metal with the π-electron systems of unsaturated organic compounds, in particular, when the unsaturated moiety carries a negative charge. The chapter also looks at one important aspect that governs the reactivity of organometallic species: the polarity of the Mδ+ Cδ-bond. It explicates the nature of bond polarity, then studies the concept of electronegativity and ‘group electronegativity’. Towards the end, the chapter turns to the reactivity of main group metal alkyls. It also considers ionic organometallics and lithium ions.
Chapter
Organometallic Compounds of Transition Metals
This chapter looks at the synthesis of lithium. It emphasizes that lithium alkyls are made by reacting alkyl halides with lithium metal. The reaction is facilitated by a solvent that can stabilize the lithium ion, such as diethyl ether. The chapter also demonstrates the synthesis of lithium alkyls by transmetallation, then outlines the structure of lithium alkyls. As strong bases, lithium alkyls are used extensively for the deprotonation of C–H bonds. The addition of chelating donor ligands such as TMEDA has proved beneficial and greatly increases reactivity. Next, the chapter examines the ortho-directing effect and stereo-differentiating lithium reagents. It also considers organometallic compounds of the heavier alkali metals — Na-Cs.
