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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.


Cover Functional Groups


This chapter focuses on the differences between alkynes and alkenes, particularly those that affect synthetic work. It explains that one difference concerns the CC double bond, which is usually created from saturated intermediates by elimination but is formed in a different way in alkynes. In these, ethene is widely used in building up the higher members and other compounds containing the triple bond. The chapter observes that alkynes are less reactive than alkenes, but with nucleophiles, the relative reactivity is reversed as simple alkenes do not undergo nucleophilic addition while simple alkynes undergo few additions. It discusses the hydrogenation of an alkyne with a poisoned catalyst that stops at the alkene stage.


Cover Organic Chemistry

Conjugation, π-Electron Delocalization, and Aromaticity  

This chapter begins with a discussion on extended π bonds and the concept of conjugation. It stresses that the C=C double bond is made up of a σ bond and a π bond, and the characteristic chemical properties of ethene come mainly from the π bond. The chapter also highlights that two C=C double bonds separated by a single σ bond are also able to interact by sideways overlap of their π molecular orbitals or MOs (called a conjugative interaction) in a conjugated system. The chapter then introduces stabilization or delocalization energy. It investigates how constituent π and p orbitals of appropriate energy and symmetry within a molecule (or ion) interact to give the new MOs of a conjugated system, and how the conjugation can be described by resonance. Next, the chapter considers the electronic structure of benzene and the nature of aromaticity.


Cover Foundations of Organic Chemistry: Worked Examples

Reactions with electrophiles  

This chapter reviews the addition of HX to C=C, the mechanisms of the reactions of HCI HBr, H2O addition to ethene and propene, carbocations, and cationic polymerization. It discusses the mechanism and stereochemistry of the addition of X2 and XY to C=C and addition to ethene and propene. It also examines the electrophilic aromatic substitution reactions, which includes aromatic compounds, halogenation, nitration, and acylation. The chapter highlights the crowding around the central carbon atom, wherein the larger C-C-C angle in the secondary carbocation keeps the other two carbon atoms further apart than they are in the primary carbocation. It talks about the electron-releasing inducive effect of two alkyl groups on the C+ that favours the secondary C+.