4.1.2- Alkanes Flashcards
What is an alkane?
A saturated hydrocarbons containing C-H bonds only
What is general formula of alkane?
Cn H2n+2
Are alkanes bonds polar? Why/ why not?
Nonpolar because carbon and hydrogen have similar electronegativities
What is shape of angle of an alkane?
Tetrahedral
109.5 degrees
Describe the sigma bond in alkane
The sigma bond is a covalent bond which has a direct overlap of the electron clouds of the bonding atoms
What type of intermolecular forces do alkanes have? Why?
London force -> induced dipole-dipole interaction, because bonds are nonpolar
What happens to the boiling point as alkane chain length increases? Why?
The boiling point increases because there is more surface area and so more number of induced dipole-dipole interaction. Therefore more energy required to overcome the attraction
Does a branched molecule has a lower or higher boiling point compared to equivalent straight chains? Why?
The branched molecule has a lower boiling point because they have fewer surface area and hence less induced dipole-dipole interactions
Are alkanes soluble in water? Explain
Insoluble because hydrogen bonds in water are stronger than alkanes’ London forces of attraction
How reactive are alkanes?
Very unreactive
What reactions will alkanes undergo?
Combustion and reaction with halogens
What type of reaction is combustion?
Oxidation reaction
What is complete combustion?
Combustion that occurs with plentiful supply of air
What are products of complete combustion of alkanes?
Carbon dioxide and water
What is colour of bunsen burner flame during complete combustion?
Blue flame
What is incomplete combustion and what are products formed with alkanes?
Combustion in a limited supply of oxygen
Products: water, carbon dioxide and carbon monoxide
What type of hydrocarbon are most likely to undergo incomplete combustion?
Longer chains
What is environmental impact of carbon monoxide?
It is toxic/ poisonous
What is the environmental impact of soot (carbon)?
Asthma, cancer, global dimming
How are haloalkanes formed from alkanes?
Radical substitution
In presence of what does alkane react with halogens?
UV light
What are the three stages of free radical substitution?
Initiation- breaking halogen bond to form free radicals
Propagation- chain part of reactions where products are formed but free radical remains
Termination- free radicals removed, stable products formed
