Module 1- Basic concepts and Hydrocarbons Flashcards
Define Hydrocarbons.
Hydrocarbons are organic compounds that contain only carbon and hydrogen atoms.
Define Unsaturated Hydrocarbons.
An Unsaturated hydrocarbon is a hydrocarbon contain carbon-to-carbon multiple bonds.
Define an Aliphatic Hydrocarbon.
An Aliphatic hydrocarbon is an hydrocarbon with carbon atoms joined together in straight or branched chains.
Define an Alicyclic Hydrocarbon.
An Alicyclic hydrocarbon is an hydrocarbon with carbons joined together in a ringed structure.
What is meant by the term “A homologous series’?
A homologous series is a series of organic compounds with the same functional group but with each successive member differing by CH2.
What is a Functional group?
A functional group is the part of the organic molecule responsible for its chemical reaction.
What is an alkyl group?
An alkyl group is an alkane with a hydrogen atom removed.
Name three stages in Free Radical substitution>
The three stages of free radical substitution are:
Initiation, Propagation and Termination.
What happens during the initiation stage of free radical substitution?
The radicals are produced at this stage. It always involves the breaking of a covalent bond by UV radiation. Because two of the same radicals are formed by the splitting this is called homolytic fission.
What happens during the propagation stage of free radical substitution.
This stage keep the reaction going because it produces radicals, making it a chain reaction.
What happens during the termination stage of free radical substitution?
This ends the chain reaction because radicals are tied up. The products of chain reactions are difficult to predict because the reactions are difficult to control.
Give five reasons why petrol is considered a “good fuel”?
Its vapour mixes easily with air/ oxygen and ignites at low temperatures.
as a liquid, it is easily transported and easy to store.
it leaves little or no residue after it is burned.
when it burns,it releases large amounts of energy and large volumes of gas that can drive a car piston.
the structures of the hydrocarbons in the petrol mixture can be altered to burn more smoothly.
What are the three main types of fossil fuel.
The three main fossil fuels are coal,oil and natural gas.
What is crude oil made up of?
Crude oil is mostly a mixture of alkanes with different boiling points.
Explain the process of cracking.
Cracking uses a high temperature and a catalyst to break up longer chain alkane molecules in alkenes and either more useful alkanes and hydrogen. It is a type of thermal decomposition.
Define Radical substitution.
Radical substitution is a type of substitution reaction in which a radical replaces a different atom or group of atoms.
Define the term mechanism.
Mechanism is a sequence of steps showing the path of electrons in a reaction.
Define the term initiation.
Initiation is the first step in a radical substitution in which the free radicals are generated by ultraviolet radiation
Describe what happens in the first propagation step.
In the first propagation step, methane reacts with a chlorine radical. A single C-H bond is broken by homolytic fission forming a .CH3 methyl radical. Hydrogen chloride, HCl is also formed.
Describe what happens in the second propagation step.
In the second propagation step, the methyl radical reacts with a chlorine molecule. The organic product is chloromethane is formed together with a further chlorine radical. The chlorine radical can be used again in the first propagation step.
Define the term termination in relation to radical substitution.
Termination is the step at the end of a radical substitution when two radicals combine to form a molecule.
Describe what happens during the termination stage.
In the termination stage, two radicals combine to form a molecule. There are a number of possible termination steps. This is because of the large numbers of radicals in the reaction mixture.
Define a pi-bond
A pi-bond is the reactive part of a double bond formed above and below the plane of bonded atoms by sideways overlap of p orbitals.
Where is a sigma bond found in the formation of a double bond?
A sigma bond is formed directly between two carbon atoms by the overlap of orbitals. Each carbon contributes one electron to the electron pair in the sigma bond.
Where is the pi-bond found in the formation of a double bond.
The pi-bond is formed above and below the plane of the carbon atoms by sideways overlap of p orbitals . Each carbon atom contributes one electron from a p- orbital to the electron pair in the pi bond.
