Hydrocarbons and Halogenoalkanes

A sigma bond is a covalent bond formed by the end-on overlap of two atomic orbitals lying along the axis of the bond

A pi bond is a covalent bond formed by the sideways overlap of two parallel atomic orbitals lyingperpendicular to the axis of the bond

Sigma bonds (as the end-on overlap is much moreefficient than side-on overlap)

The process of mixing atomic orbitals in an atom to generate a set of new atomic orbitals called hybrid orbitals

• sp³ bonding is when the three 2p orbitals and one 2s orbital mix to form degenerate hybrid orbitals
• Alkanes

• sp² bonding is when the 2s orbital and two 2p orbitals mix to form hybrid orbitals
• Alkenes

chain reaction

• Initiation
• Propagation
• Termination

Ultraviolet light provides energy for the reaction to start. Homolytic fission of Cl or Br occurs. This creates free radicals (atoms or groups or atoms with an unpaired electron) which are highly reactive.

• Each chlorine radical that is produced goes on to attack a methane molecule removing a hydrogen atom from it to form HCl and a methyl radical: Cl^. + CH₄ ---> HCl + CH₃^.
• The methyl radical then attacks a chlorine molecule to form chloromethane and another chlorine radical: CH₃^. + Cl₂ ---> CH₃Cl + Cl^.
• In each of the propagation steps one radicalsenders the reaction and another radical is generated . These steps sustain the reaction.

• Reactions in which radicals are used up and noT regenerated eg 
• CH₃^. + Cl^. ---> CH₃Cl
• CH₃^. + CH₃^. ---> CH₃CH₃
• Cl^. + Cl^. ---> Cl₂

• Dehydration of alcohols
• Base-induced elimination of hydrogen halides from monohalogenoalkanes

By passing them over hot aluminium chloride or using concentrated sulphuric acid or orthophosphoric acid

Alkanes

Dihaloalkanes

Monohalogenoalkanes

Alcohols

• Hydrogenation
• Nickel or platinum

Halogenation

Hydrohalogenation

• Hydration
• Acid

Marokovinikov's rule states that when H-X or H-OH adds onto an unsymmetrical Allende the major product is the one in which the H atom ends up attached to the carbon atom of the double bond which already has the greater number of hydrogen atoms bonded to it

• A cyclic ion intermediate
• A carbocation intermediate
• A carbocation intermediate

• Primary - halogen atom on carbon attached to 1 other carbon atom
• Secondary - halogen atom on carbon attached to 2 carbon atoms
• Tertiary - halogen atom on carbon attached to 3 carbon atoms

Nucleophilic substitution

Alkenes

Alcohols

Ethers

Nitriles (which can be hydrolysed to carboxylic acids)

Amines