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Chapter

Cover Chemistry3

Carboxylic acids and derivatives  

Nucleophilic acyl substitution and α-substitution reactions

This chapter focuses on carboxylic acids and derivatives, which are a large family of compounds that have similar structures as they all contain a C=O bond joined to an electronegative atom, typically oxygen, nitrogen, or a halogen atom. Esters, acid anhydrides, amides, and acyl chlorides are called carboxylic acid derivatives because they can be prepared from carboxylic acids. The chapter describes a general mechanism for a nucleophilic acyl substitution reaction and explains why carboxylic acid derivatives react with nucleophiles in substitution reactions rather than addition reactions. It discusses keto–enol tautomerism in carboxylic acid derivatives and the factors that influence the stability of keto and enol forms. It also shows how to predict the structure of a product derived from a nucleophilic acyl substitution, an α-substitution, or a carbonyl–carbonyl condensation reaction of a carboxylic acid derivative.

Chapter

Cover Elements of Physical Chemistry

Molecular orbital theory: heteronuclear diatomics  

This chapter looks at the molecular orbital theory (MO theory) of heteronuclear diatomic molecules and ions, which introduces the possibility that atomic orbitals on two atoms contribute unequally to the molecular orbital. It points out how polarity can be expressed in terms of the concept of electronegativity. It also examines the bonding molecular orbital of a heteronuclear diatomic molecule or ion which is composed mostly of the atomic orbital of the more electronegative atom. The chapter describes the electron distribution in the covalent bond between the atoms in a heteronuclear species, which is considered not symmetrical between the atoms as it is energetically favourable for a bonding electron pair to be found closer to one atom rather than the other. It mentions the polar bond, which is a covalent bond in which the electron pair is shared unequally by two atoms.

Chapter

Cover Pharmaceutical Chemistry

The Carbonyl Group and its Chemistry  

Matthew Ingram

This chapter discusses the nature of the carbonyl group and the chemistry it can undergo. The chemistry of the carbonyl group can be found in lots of situations: in the body, in the environment, in manufacturing, and in pharmaceutical applications. At the heart of the chemistry of the carbonyl group is the carbonyl bond, a double bond comprising one σ and one π bond, which joins carbon and oxygen. The chapter points out the difference in electronegativity between carbon and oxygen, citing a dipole moment that exists between the two atoms. The carbonyl group is central to pharmaceutical chemistry and is present in many drug molecules and is present in many different types of compound.

Chapter

Cover Organic Chemistry

Atoms, Molecules, and Chemical Bonding—a Review  

This chapter presents an overview of organic chemistry and looks at the compounds of carbon. It argues that there are hugely more compounds of carbon than of all other elements combined. The chapter then discusses the special properties of the element, and the characteristics of the carbon atom. It begins the study of organic chemistry by reviewing the nature of atoms and, in particular, their electronic structures. The chapter also looks at valence electrons and ionic and covalent bonds. It then explains the method of representing atoms which gave prominence to their valence electrons and facilitated comparisons between different elements. The chapter then demonstrates the periodic table by looking at the Lewis representations of atoms. Finally, the chapter analyzes several scales to quantify electronegativity. It also considers bond polarity and an introduction to resonance.

Chapter

Cover Making the Transition to University Chemistry

The Halogens  

This chapter discusses the halogens, also known as either Group 17 or Group VII. It also notes the exception of featuring astatine due to its high radioactivity. The physical properties of the halogens range between the melting points, boiling points, atomic radius, ionic radius, electronegativity, ionization energy, and dispersion forces. Additionally, the oxidizing ability of the halogens decreases in positivity, while the reducing ability of the halide ions increases. Fluorine is known to be exceptionally strongly oxidizing. Aqueous halide ions are tested by adding aqueous silver nitrate acidified with dilute nitric acid. An equilibrium is set up when chlorine dissolves in water.

Chapter

Cover Making the Transition to University Chemistry

Bonding and Molecular Shape  

This chapter discusses bonding and molecular shape of electrons. A covalent bond occurs when atoms share a pair of similar electrons. Modern theories on covalent bonding are dominated by molecular orbital theory. Polar covalent bonds occur when different atoms share the electron pair unequally due to electronegativity. With benzene being the most familiar molecule of the bonding, delocalization happens when more than two atoms are involved in the bonding. The valence-shell electron-pair repulsion (VSEPR) theory can help us to visualize the shapes of simple molecules. Additionally, ionic bonding occurs when an atom transfers an electron to another atom and the ions formed a crystal lattice electrostatically.

Chapter

Cover Inorganic Chemistry

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

Cover Making the Transition to University Chemistry

Transition Metals 1  

This chapter discusses the halogens, also known as either Group 17 or Group VII. It also notes the exception of featuring astatine due to its high radioactivity. The physical properties of the halogens range between the melting points, boiling points, atomic radius, ionic radius, electronegativity, ionization energy, and dispersion forces. Additionally, the oxidizing ability of the halogens decreases in positivity, while the reducing ability of the halide ions increases. Fluorine is known to be exceptionally strongly oxidizing. Aqueous halide ions are tested by adding aqueous silver nitrate acidified with dilute nitric acid. An equilibrium is set up when chlorine dissolves in water.

Chapter

Cover Organometallics and Catalysis

Homogeneous Catalysis with Organometallic Transition Metal Complexes  

This chapter stresses that alkaline earth elements are more electronegative than the alkali metals and that their M–C bonds are more covalent. It emphasizes that alkaline earth compounds are Lewis acids and can coordinate two or more neutral ligands. This Lewis acidity is responsible for their high reactivity. The chapter then presents the bonding characteristics of Beryllium, as the alkaline earth element with the smallest radius. It shows the synthesis of magnesium and the formation of Grignard reagents. It also reviews how the metal–halogen exchange and C–H metallation. Next, it examines the structures of magnesium reagents and the reactions of magnesium reagents. The chapter then analyses the organometallic derivatives of the heavier alkaline earth metals — calcium, strontium, and barium.

Chapter

Cover Foundations of Organic Chemistry: Worked Examples

Reactions with radical intermediates  

This chapter discusses the formation and nature of radicals, chain reactions, the use of fish-hook arrows, the halogenation of hydrocarbons, and the radical polymerization of alkenes. It looks at single bonds between two electronegative elements which are relatively weak, as the result of the interelectron repulsion between the nonbonded pairs of electrons on adjacent atoms. It also mentions chloroform (CHCl3), which was one of the first general anaesthetics to be discovered. Its usage has declined due to serious side-effects, and in fact anaesthetics used today are more effectiveand less toxic. The chapter highlights radical polymerization. This proceeds by addition of a radical to a multiple bond of the monomer. The chapter cites double bond that is retained in the polymer.

Chapter

Cover Foundations of Organic Chemistry: Worked Examples

Acids and bases  

This chapter discusses equilibria and factors effecting acidity and basicity of organic compounds and other areas of chemistry, such as electronegativity of the atom that bear the charge. It examines delocalization, resonance, inductive effects, indicators, and interactions between molecules and ions. It also deals with the protonation on the carbonyl oxygen atom that gives the more stable, delocalized protonated form of the COOH group. The chapter mentions the inductive electron-withdrawing effect of the C=O that helps to weaken the adjacent O-H bond and carboxylic acids that are more acidic than alcohols, whose anions are not stabilized by delocalisation. It refers to Tenormin, which is a drug used in the treatment of high blood pressure, angina, and abnormal heart rhythms.

Chapter

Cover Inorganic Chemistry in Biology

The p-block  

This chapter focuses on the p-block of elements, wherein the filling of three p-orbitals is being completed using six electrons in each series. It explains how elements become more electronegative as the p-orbitals fill as there is a driving force to accept electrons to reach a stable configuration of the noble gases. It also mentions the d-block elements that are essential components of many of the metalloenzymes that catalyse bond cleavage and overcome intrinsic low reactivity. The chapter discusses electrons that are supplied by the FE(II) form of ferredoxin and the ammonia produced for the synthesis of organic compounds required for cell growth. It describes enzyme that contains both an Fe protein and MoFe protein.

Chapter

Cover Essentials of Inorganic Chemistry 2

Zintl isoelectronic relationships  

This chapter examines Zintl isoelectronic relationships. The chapter starts by noting how many binary compounds are formed between the Group 1 and 2 elements and Groups 13–15. The Zintl concept utilizes isoelectronic relationships in order to provide some insight into the solid state structures adopted by such compounds. The chapter highlights that the electronegativity differences between the atoms are sufficiently large in these compounds that, to a first approximation, an ionic formulation is reasonable. The isoelectronic relationship is then used as a basis for rationalizing the manner in which the Group 13–15 elements aggregate in the solid state. Next, the chapter explains that many of the anionic species observed in Zintl phases in the solid state are not observed as stable solution species. This is because their large negative charges make them very nucleophilic and therefore sensitive to the slightest traces of moisture.

Chapter

Cover Inorganic Chemistry in Biology

The d-block - redox chemistry  

This chapter explains the d-block of elements as a family of metals with similar characteristics that represent the transition between the highly electropositive s-block metals and the electronegative p-block non-metals. It discusses the behaviour of d-block elements as ions in solution and relates this to coordination and redox chemistry. It also examines transition elements that exhibit variable oxidation states, such iron that exist in oxidation states of II, III, IV, and VI. The chapter describes the octahedral arrangement of the six d electrons that can be in two dispositions and the possible dichotomy that plays an important role in iron-protein chemistry. It mentions a pair of Fe(II) and Fe(III) ions that behave like an isolated metal centre.

Chapter

Cover NMR Spectroscopy in Inorganic Chemistry

Factors influencing the chemical shift and coupling constants  

This chapter surveys the chemical factors that influence the chemical shift and the magnitude of coupling constants. Shielding is influenced by the fields generated by circulation of ground state electrons around the nucleus (diamagnetic term) and by electrons mixed in from excited states (the paramagnetic term). The diamagnetic contribution is usually small and dominates for light elements, resulting in (usually) small chemical shift ranges for these elements. The paramagnetic term dominates for heavier elements and is often large, resulting in large chemical shift ranges for these elements. The chemical shift is influenced by many, often competing factors, including oxidation state, electronegativity, coordination number, and bonding to other atoms. Meanwhile, scalar coupling constants are influenced by similar factors and by geometric factors, particularly interbond and dihedral angles. If all other factors are kept constant, scalar couplings between different isotopes of the same elements scale with gyromagnetic ratio.

Chapter

Cover Periodicity and the s- and p-Block Elements

Periodicity in the properties and structures of the elements  

This chapter examines the properties of the elements themselves and provides an understanding of the origin of the observed periodic trends. The first, and perhaps most important, point to note is that the p-block is the only part of the periodic table which contains non-metals. Moreover, within the p-block, the metals are found in the bottom left-hand corner while the so-called metalloids or semi-metals lie along a diagonal from top left to bottom right with the non-metals occupying the top right. There is, therefore, a trend from metallic to non-metallic character as we move from bottom left to top right. This pattern correlates precisely with the trend seen for the element electronegativity discussed in the previous chapter. A final point of interest while dealing with the elements themselves concerns the so-called binding energies (or atomization energies), which relate to the magnitude of the interatomic forces which bind the elements together.

Chapter

Cover Organometallics and Catalysis

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

Cover Periodicity and the s- and p-Block Elements

Compounds of the s- and p-block elements  

This chapter assesses s- and p-block element compounds and their properties. It begins by looking at halides, which is a large and diverse group of compounds, particularly in terms of the variety of structural types encountered. Halides include fluorides and chlorides. The chapter then considers ionic compounds, element oxides, and element hydrides. All the hydrides are molecular covalent species, but the trends in melting and boiling points are worthy of comment. In Group 14, one sees a progression to higher melting and boiling points as the group is descending resulting from the increasing van der Waals forces between the molecules. This is also largely the case for the Group 16 hydrides but with the obvious exception of H2O. The explanation for this feature is the extensive intermolecular hydrogen bonding between oxygen lone pairs and hydrogen, this being that much greater for the lighter element oxygen due to its high electronegativity.

Chapter

Cover Periodicity and the s- and p-Block Elements

Periodicity in the properties of s- and p-block atoms  

This chapter discusses a range of properties of isolated atoms of the s- and p-block elements which will introduce the ideas of periodicity. It begins by looking at the idea of effective nuclear charge, which is useful in understanding many aspects of periodicity; but in order to utilize and appreciate the concept fully, a quantitative scale is desirable whereby we can look at values and trends in values for the valence electrons of the elements in which we are interested. The chapter then considers ionization energies and electron affinities. The ionization energy is the energy required to completely remove an electron from an atom in the gas phase, while the electron affinity of an atom is defined as the energy change which occurs when an electron is added to an atom (or ion). The chapter also studies covalent and ionic radii; electronegativity; orbital energies and promotion energies; and relativistic effects.

Chapter

Cover Essentials of Inorganic Chemistry 1

Effective atomic number rule to exchange energy  

This chapter assesses the effective atomic number rule. The effective atomic number rule applies to molecules where covalent bonding is strong and all the valence orbitals are being used in either homo- and hetero-polar covalent bonds or are occupied by non-binding electron-pairs. If the molecule is unable to achieve the octet or 18-electron configurations by virtue of donation from the ligands, then element–element bonds may be formed. The chapter then looks at electrode potential, before considering electron affinity and deficiency. The electron affinity is the negative of the electron capture enthalpy, while an electron deficient molecule has fewer valence electrons involved in covalent bonds than the number of orbitals available. The chapter also studies electronegativity, the electroneutrality principle, electropositivity, entropy, and exchange energy.