unit 4-Alkanes Flashcards
What is a covalent bond?
A shared pair of electrons.
What is a sigma bond?
The overlap of two orbitals, one from each bonding atom.
What is the shape and bond angle of carbons in an alkane & why?
Tetrahedral, 109.5, 4 bonding regions.
How is the boiling point of an alkane affected by its chain length?
As the chain length increases, so does the boiling point.
Why does chain length affect the boiling point of an alkane?
As the chain length increases, the molecules have a larger surface area, meaning more London forces which require more energy to overcome.
Do branched isomers have a higher or lower boiling point than straight chain alkanes?
Lower.
Why do straight chain alkanes and branched alkanes have different boiling points? (2 points)
(1)There are fewer points of contact in branched isomers, giving fewer Londion forces.
(2) The branches make it harder for the molecules to get as close together as straight chain molecules, meaning less surface area, giving weaker London forces.
Why do alkanes not react with most reagents? (3 points)
(1) Sigma bonds are strong.
(2) C-C bonds are non-polar.
(3) C-H bonds can be considered non-polar due to the similarity in electronegativity of C and H.
Why are alkanes used as fuels?
combust easily, easy to transport and don’t release toxic byproducts.
What is the danger of incomplete combustion?
CO is produced, toxic. Binds to haemoglobin irreversibly and prevents transportation of oxygen.
When can alkanes react with halogens?
In the presence of UV radiation (sunlight).
What is a radical?
A very reactive species with an unpaired electron.
What is a structural isomer?
When molecules have the same molecular formula but different structural formula.
What is homolytic fission?
What is a homologous series?
A series of compounds with the same functional group, when each successive member differs by CH2.
