Alkanes Flashcards
Generic formula for alkanes
C(n)H(2n+2)
Describe the bonding of alkanes
Single covalent sigma bond
Fully saturated
Can rotate
What is a sigma bond
End to end overlap of orbitals
Single covalent bond
Describe the shape of alkanes
Tetrahedral (4 bonds per carbon atom)
Bond angle in alkanes
109.5
What effect does increasing the length of the carbon chain have on boiling point? Why?
BP increases
More surface contact points so stronger London forces
What affect does increasing branching have on boiling point? Why?
Decrease BP
Less compact, weaker and fewer London forces
Less surface contact points, weaker London forces
Describe the reactivity of alkanes and state why
Lack of reactivity
Due to strong sigma bonds and lack of polar bonds
Why are alkanes used as fuels?
Readily available
No toxic byproduct when combusted
Easy to transport
What may form in incomplete combustion?
CO or C
(not both)
+H2O
Give an example of a substitution reaction with alkanes
+ Halogen
Halogen substitutes H
State steps in radical substitution
Initiation
Propagation
Termination
Explain radical substitution
A Halogen radical substitutes a H in a hydrocarbon
Describe initiation
Covalent bond in Halogen is broken by homolytic fission is presence of UV radiation
What occurs during initiation?
Photodissociation