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Chapter

Cover Pharmaceutical Chemistry

Properties of Aliphatic Hydrocarbons  

Andrew J. Hall

This chapter details how molecules that have short or long chains or more complicated arrangements of carbon atoms can be produced. Hydrocarbons are compounds made solely of carbon and hydrogen atoms, in which each carbon forms four covalent bonds. The chapter highlights the importance of hydrocarbons in everyday lives as they are a source of energy used to heat and light homes, power vehicles, and provide many of the plastic items being used. The chapter talks about the abundance of hydrocarbons in nature, such as flavours or fragrances produced by plants, insect pheromones, and natural rubber and lipids. It explores the properties of the aliphatic hydrocarbons: the alkanes, alkenes, and alkynes.

Chapter

Cover Chemistry3

Benzene and other aromatic compounds  

Electrophilic substitution reactions

This chapter considers benzene as one of the most fascinating organic molecules. Six carbon atoms in benzene are linked in a planar hexagon and, as each carbon atom is bonded to only one hydrogen atom, benzene is an unsaturated hydrocarbon. The chapter determines what aromatic, antiaromatic, and nonaromatic compounds are and give examples of each. It identifies reagents and reaction mechanisms to explain how benzene undergoes halogenation, nitration, sulfonation, Friedel–Crafts alkylation, and Friedel–Crafts acylation. It also talks about how the electronic and steric effects of substituents on benzene rings influence the rates and regioselectivities of electrophilic substitution reactions and how substituents on benzene rings can be converted into other substituents by redox reactions or by forming diazonium ions.

Chapter

Cover Making the Transition to University Chemistry

Hydrocarbons: Alkenes  

This chapter focuses on alkenes, which are known to be unsaturated hydrocarbons with a carbon-carbon double bond. Ethene is known to be the simplest alkene, this is closely followed by propane. Alkenes undergo electrophilic addition reactions. This involves the addition of hydrogen halides, acidified water, and halogens. The chapter explains the Markovnikov's rule wherein the alkene and adduct are unsymmetrical. This is something which two isomers could form. Markovnikov's rule refers to the more stable carbocation forms carrying a positive charge with three bonds. The chapter also explicates the addition of a neutral molecule to ethene which is largely similar to the electrophilic addition of molecules under acidic conditions.

Chapter

Cover Aromatic Chemistry

Polycyclic arenes  

This chapter discusses polycyclic arenes. The fusion of benzene rings leads to an array of polycyclic arenes, of which naphthalene, anthracene, and phenanthrene are the best known. Other compounds in the series include chrysene, pyrene, tetracene, and coronene. Many polycyclic aromatic hydrocarbons are found in coal tar, and are formed when plant materials are partially combusted. Some are procarcinogens, that are oxidized within the body to the true cancer-promoting compounds. Very large polycyclic systems are known, and graphite consists of planes derived from an infinite linear fusion of benzene nuclei. Naphthalene is much more easily hydrogenated than benzene, but the reduction only proceeds as far as 1,2,3,4-tetrahydronaphthalene (tetralin). Meanwhile, anthracene can be synthesized in several ways, two of which parallel the constructions of naphthalenes.

Chapter

Cover Making the Transition to University Chemistry

Hydrocarbons: Arenes  

This chapter discusses arenes, a type of hydrocarbon. Benzene is known to be the archetypal arene as it features the original Kekulé structure with alternating double and single bonds. The electrophilic substitution reactions of benzene go in line with the high electron density above and below the benzene ring. Nitration is a particularly vital reaction undergone by benzene. This involves a nitrating mixture of concentrated nitric acid and sulfuric acid. Additionally, the electrophilic substitution of Friedel–Crafts acylation involves reagents of acyl chloride and aluminium chloride , the latter which acts as a Lewis acid. On the other hand, the electrophilic substitution of halogenation pertains to how benzene needs a catalyst for halogenation.

Chapter

Cover Making the Transition to University Chemistry

Hydrocarbons: Alkanes  

This chapter tackles the concept of alkanes, a type of hydrocarbon. It defines a hydrocarbon as containing hydrogen and carbon only. Alkanes are saturated hydrocarbons. Crude oil is an example of a complex mixture of hydrocarbons, most of which are alkanes. Fractional distillation allows for the separation of the mixture and relies on the different fractions with varying boiling points. The chapter explores the mechanism for radical chain reaction and photochemical halogenation which occur through the reaction of an alkane with a halogen. Finally, the combustion of alkanes is considered to be the most significant reaction commercially since it is also a radical chain reaction.

Chapter

Cover Organic Chemistry

Organic Compounds: their Functional Groups, Intermolecular Interactions, and Physical Properties  

This chapter highlights that a molecule of an organic compound generally consists of what we call a functional group and a hydrocarbon residue. It notes that the distinctive properties of the compound are principally due to the functional group. The functional group consists of a few atoms bonded together and they react as a unit. Consequently, organic compounds are classified and named according to their functional groups. The chapter identifies the principal classes of organic compounds covered in this book and looks at how to name them. It assesses how some properties of a compound can only be understood in terms of large assemblies of molecules and the physical interactions between them (as opposed to properties of individual isolated molecules). The chapter also studies the elements of organic nomenclature, and further elaborates on the intermolecular interactions and physical properties of organic compounds.

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 Polar Rearrangements

Carbocation induced alkyl and hydride shifts  

This chapter recounts the accumulation of structural information by early investigations in the nineteenth century of components of essential oils of plants to establish basic family likeness. It analyses the volatile and fragrant compounds that were found to be unsaturated hydrocarbons and their oxygenated derivatives contain carbon atoms. It also talks about Hans Meerwein, who generalised the carbocationic mechanism to account for some terpenic rearrangements. The chapter examines the fate of the rearranged carbocation which depends on the structure of the molecule and involves quenching by elimination or addition of a nucleophile. It talks about a rearrangement that may occur to give a more stabilized carbocation and become a basis of the biological construction of complex terpene molecules.

Chapter

Cover Chemistry for the Biosciences

Hydrocarbons: the framework of life  

This chapter introduces organic chemistry, the chemistry of carbon and carbon-containing compounds. Carbon has an important structural role in organic compounds because of its high valency. Organic compounds have a simple hydrocarbon framework, to which are attached more specialized groups of atoms. The chapter then looks at the three different types of hydrocarbon: alkanes, which contain only single carbon–carbon bonds; alkenes, which contain at least one double carbon–carbon bond; and alkynes, which contain at least one triple carbon–carbon bond. A special hydrocarbon group is the aryl group, which is derived from an aromatic hydrocarbon by the removal of one or more hydrogen atoms. Finally, the chapter explores the physical and chemical properties of the hydrocarbons.

Chapter

Cover Radical Chemistry: The Fundamentals

Autoxidation - a case study  

This chapter deals with the aspects of autoxidation, complexities that are important with particular substrates. It also looks at the ramifications of autoxidation in biological systems. The chapter outlines the chain-propagating steps for autoxidation, which include the abstraction of hydrogen from substrate. It also mentions the durability of commercial products in the case of hydrocarbons, such as might be enhanced by the minimization of the number of relatively weak tertiary C-H bonds in the molecular structure. The chapter details how initial hydrogen abstraction forms a stabilized pentadienyl radical which that combines with oxygen at a terminal carbon. It looks at the resulting peroxyl radical that abstracts hydrogen from a second skipped diene and gives a hydroperoxide.

Chapter

Cover Alicyclic Chemistry

Polycyclic systems  

This chapter refers to bi- and polycyclic hydrocarbons that are named according to the way in which the component rings are fused to each other. It describes heptane, also known as norbornane, as one of the best studies bicyclic systems. It also discusses the derivatives of the hydrocarbon, which have several interesting properties that partly arise from strain present in the structure and provide a useful framework for testing aspects of reactivity and mechanistic pathways. The chapter highlights features of the reactions of 2-norbornyl derivatives, which includes the occurrence of skeletal rearrangement in which the 2-norbornylcation is an intermediate. It analyses the basis of Bredt's rule, which implies that an elimination process in a bridged structure should always avoid the formation of an alkene at a bridgehead.

Book

Cover Pharmaceutical Chemistry

Chris Rostron and Jill Barber

Pharmaceutical Chemistry opens with an examination of the importance of pharmaceutical chemistry. It then turns to organic structure and bonding and stereochemistry and drug action. The next chapter looks at aliphatic hydrocarbons. There follows a chapter on alcohols, phenols, ethers, organic halogen compounds, and amines. Other topics covered include the carbonyl group, aromatic chemistry, inorganic chemistry, nucleic acids, and proteins and enzymes.

Chapter

Cover Organic Chemistry

Organic structures  

This chapter discusses the process of interpreting organic structures and drawing organic molecules. Organic chemistry is the study of compounds that contain carbon. Nearly all organic compounds also contain hydrogen; most also contain oxygen, nitrogen, or other elements. Organic chemistry concerns itself with the way in which these atoms are bonded together into stable molecular structures, and the way in which these structures change in the course of chemical reactions. The chapter then looks at hydrocarbon frameworks and functional groups. It also considers how carbon atoms carrying functional groups can be classified based on oxidation levels, before explaining the process of naming compounds.

Chapter

Cover Foundations of Organic Chemistry

Reactions with radical intermediates  

This chapter addresses homolytic reactions which involve radical intermediates. A radical has an odd unpaired electron and is normally uncharged. Radicals are electron-deficient in the sense that the atom carrying the unpaired electron is one electron short of a stable outer shell, such as carbon or chlorine with seven electrons instead of eight. The formation of radicals at the beginning of a reaction is called the initiation. The reaction then continues by the propagation steps, in which a radical reacts with a molecule to give another radical as one of the products. The propagation steps can go on and on to make a chain reaction, until two radicals combine to form a stable compound (termination reaction). The chapter then looks at the halogenation of hydrocarbons; catalytic hydrogenation; and the cracking of hydrocarbons. It also considers the radical polymerization of alkenes; enzyme-catalyzed radical reactions; and radical reactions in the gas phase.