Download Chemical Reactions: Combustion, Substitution, and Addition with Hydrocarbons and more Lecture notes Organic Chemistry in PDF only on Docsity!
Lesson 9 Chemical reactions with alkanes, haloalkanes and alkenes.
Click to revise reaction pathways
Saturated hydrocarbon = a compound that has single carbon to carbon bonds (C-C) and is composed of hydrogen and carbon atoms only. Unsaturated hydrocarbon = a compound that has one or more double carbon to carbon bonds (C=C) or even a triple carbon to carbon bond and is composed of hydrogen and carbon atoms only.
All alkanes and alkenes undergo combustion with oxygen to produce carbon dioxide and water. In fact hydrocarbons will undergo combustion in oxygen to produce CO 2 and H 2 O. a) 2C 2 H 6 (g) + 7O 2 (g) 4CO 2 (g) + 6H 2 O(g)
b) C 2 H 4 (g) + 3O 2 (g) 2CO 2 (g) + 2H 2 O(g)
Alkanes undergo reactions known as substitution reactions where a hydrogen is substituted for a chlorine or some other halogen. This usually occurs in the presence of UV light.
Haloalkanes can the be used in further substitution reactions to produce other beneficial compounds. Chloroethane, for example, can undergo a substitution reaction with NaOH to produce ethanol
Ethanol can also be produced via a substitution reaction between chloroethane and water in the presence of a catalyst.
Not only alcohols can be produced via substitution reactions with haloalkanes but amines as well via reactions with ammonia.
Addition reactions. As the name implies addition reactions involve the addition of a small molecule across the double bond of an alkene.
The reaction above, where water is used as a reactant is sometimes referred to as a hydration reaction.
Alkenes can also undergo addition reactions to form long chain polymers. This type of reaction is known as addition polymerisation. Alkenes can attach to each other across the double bond.
Eg Polyvinyl chloride (PVC) is a durable and versatile plastic. It is made from chloroethene monomers. Monomers are the small molecules that join to form long molecules, generally known as polymers.
- Write a balanced chemical equation for the combustion reaction of octane. 2C 8 H 18 (l) +25 O 2 (g) 16CO 2 (g) + 18H 2 O(g)
- For each of the reactions below identify X a) X = 2-chlorobutane
b) X = but-2-ene CH 3 c) X = prop-2-ene
trans-pent-2-ene reacts with Cl 2 in an addition reaction. Name all the possible isomers that are possible and give write their structural formulae. 2, 3-dichloro pentane
Styrene is a plastic commonly used for plastic and plastic cutlery. The repeating unit in the polymer chain is shown on the right. Draw the monomer of this polymer. What type of reaction forms this plastic? Addition polymerisation
Identify each species involved in the reaction pathways shown below. Identify the type of reaction that takes place at each step.
a) A = 2-chloropropane, formation of A is an addition reaction, B = propene
