4.1 - Basic Concepts and Hydrocarbons
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Define the term homologous series
A series of organic compounds having the same functional group ad with each successive member differing by CH2.
Define the term functional group
A group of atoms responsible for the characteristics of a compound
What is meant by an aliphatic compound?
A compound containing carbon and hydrogen joined together in straight chains, branched chains or non-aromatic rings e.g. butane
What is meant by an alicyclic compound?
An aliphatic compound arranged in non-aromatic rings or without side chains E.g. cyclohexene
What is meant by an aromatic compound?
A compound containing at least one benzene ring e.g. Benzene
Define the term saturated
A molecule that only has single carbon to carbon bonds
Define the term unsaturated
A molecule that contains at least one carbon doubled bonded to another carbon atom
Define the term structural isomer
Compounds with the same molecular formula but different structural formulae e.g. butane and 2-methylpropane
What forms can structural isomers occur in?
Chain isomers (different chain length) Positional isomers (functional groups in different positions Functional group isomers (Completely different functional groups)
Do structure isomers have the same PHYSICAL properties?
No they don’t!/ They possess different physical properties such as BP, MP, and differences in density
Do structure isomers have the same CHEMICAL properties?
Most isomers show SIMILAR chemical properties if the same functional group is present. However, it is best to have a look at each structure and apply any knowledge of the chemical which is given to us in the question
Define heterolytic fission
The unequal breaking of a covalent bond, in which one bonding atom receives BOTH electrons from the bonding pair, forming OPPOSITELY CHARGED IONS.
Define homolytic fission
The equal breaking of a covalent bond, in which each atom receives ONE electrons from the bonding pair, forming 2 radicals.
Define the term radical
A high reactive species with an unpaired electron.
Give an overview of alkanes
• Saturated - Each carbon atom has 4 bonds - Usually aliphatic - General formula of CnH2n+2
Explain the tetrahedral shape and bond angle around each carbon atom in terms of electron pair repulsion
Each carbon atom has 4 bond pairs. So they will repel each other equally. This means that the molecule forms a tetrahedral shape around each carbon.
What bond angle do alkanes have?
109.5
Explain why longer chained alkanes have a higher boiling point than shorter chained alkanes
Between the molecules in an alkene, there are induced dipole-dipole interactions. The longer the carbon chain, the larger the surface area. As the surface area increases, it means that there are more induced dipole-dipole forces and these forces. Therefore, as molecules get longer, it takes MORE ENERGY to overcome the induced dipole-dipole interactions, resulting in a higher BP.
Explain how branching effects the boiling point of alkanes?
Branched chains are less compact than straight chains. This means that they can’t pack closely together and they have a smaller surface contact. This means that they have less induced dipole-dipole interactions, so a lower BP.
Explain the low reactivity of alkanes in terms of bond enthalpy
Alkanes have sigma bonds. These sigma bonds have a high bond enthalpy so are difficult to break
Explain the low reactivity of alkanes in terms of polarity
The bonds in alkenes are non-polar so they don’t attract nucleophiles or electrophiles. This means that alkanes don’t react easily.
What products are produced in complete combustion
CO2 + H2O
What products are produced in incomplete combustion
CO + H2O or C +H2O