Alkanes Flashcards
What is bond fission?
Breaking of bonds
What does a covalent bond consist of?
Covalent bond consists of a shared pair of electrons
When a covalent bond breaks a bond can break two ways:
Homolytic fission
Heterolytic fisson
What is homolytic fission?
Equal sharing of the electrons in the covalent bond.
Each participant in the bond receives an electron when they split.
Forms two free radicals
How is a free radical shown?
Dot by the element
Why are free radicals extremely reactive?
The unpaired electron results in a strong tendency to pair up with another electron from another substance.
The reaction of one free radical can lead to a chain reaction as there is the formation of another free radical.
When does homolytic fission usually occur?
In situations where there is little or no ionic character in the covalent bond
The movement of an individual electron is shown as..
Single headed arrow
The movement of an electron pair is shown as..
Double headed arrow
What is a free radical?
An atom containing an unpaired electron due to the splitting of a covalent bond in homolytic fission.
What is heterolytic fission?
Unequal sharing of electrons of the covalent bond, so that both electrons go to one atom.
What is formed in heterolytic fission?
Two charged particles - Ions
When does heterolytic fission usually occur?
When a covalent bond has a degree of polarity
Why are alkanes useful?
Very un reactive apart (except combution)
Non corrosive with metals - good lubricating oils
Harmless to skin
At room temp:
Unaffected by concentrated mineral alkalis (e.g NaOHaq)
Unaffected by oxidising agents (e.g Potassium Manganate VII)
Do not react with the most reactive metals
Why are alkanes very unreactive?
C-C and H-C bonds evenly share electrons as the electronegativities of C and H are v. close. This means the bond is strong and hard to break.
Alkanes are not polar so do not attract other polar or ionic substances.
