FC16 - Alkanes Flashcards
What are hydrocarbons?
Compounds containing hydrogen and carbon only
What is a functional group
An atom or group of atoms that gives a compound its characteristic chemical properties
What is a homologous series
A series of compounds that have the same general formula but each successive member differ by an additional CH2 unit
What does saturated mean
A compound that contains only single bonds between carbon atoms
What does unsaturated mean
A compound that contains at least one double or triple bond between carbon atoms
What is the general formula of alkanes?
CnH2n+2
Define Alkanes
Saturated hydrocarbon with no specific functional group
General formula for a cyclic alkane
CnH2n
What does homolytic fission form and describe them
Radicals - species with an unpaired electron
Why are radicals so reactive
Because they readily acquire electrons to form non - radicals
What does heterolytic fission form
Ions
Describe homolytic fission
The breaking of a covalent bond where one electron from the bond remains with one of the atoms and the other electron remains with the other atom that formed the bond
Describe heterolytic fission
The breaking of a covalent bond where both electrons forming the bond remain with one atom so the other atom forming the bond loses both forming electrons
Why is there a low yield of reactions involving radicals
Radical substitutions lead to many side reactions, these include substitution at different positions on the hydrocarbon and further substitutions. This leads to many different byproducts so the yield of the desired product would be low
Define structural isomerism
Compounds with the same molecular formula but different structural formula
Define volatility
How readily a liquid vaporises, low boilng point = high volatility
Why does more branching of the same isomer result in higher volatility?
More branching means weaker London forces as there is a smaller surface area for contact, and so less energy is needed to overcome these forces therefore higher volatility
What products in complete combustion of an alkane
Carbon dioxide + water
What products in incomplete combustion of an alkane
Carbon monoxide + water
What products in very incomplete combustion of an alkane
’ Carbon + water
When does incomplete combustion occur and why is it bad?
When there is limited availability of oxygen. Bad because Carbon monoxide is an odourless, colourless toxic gas that can be fatal in high concentrations
Describe simply what happens in the halogenation of alkanes
U.V. Light breaks halogen-halogen bond (not c-h bond as c-h bond is stronger), bi-product is always hydrogen halide, in main product - one H is replaced with halogen
Define aliphatic compounds
organic compounds with no benzene ring (C6H6)
Define alicyclic compounds
aliphatic compounds with at least one ring of carbon atoms that are not benzene rings
Define aromatic compounds
organic compounds with at least one benzene ring
What is a benzene ring
cyclic alkane (6 carbons), with 3 double bonds inside (C6H6)
