alkanes

Question 1

describe the bonding in alkanes

Answer 1

-single,saturated
-sigma bond between two carbon atoms by the direct single overlap of orbitals directly between bonding atoms
-allows free rotation of the sigma bond

Question 2

explain relationship between carbon chain length and boiling point

Answer 2

-as carbon chain length increases so does the boiling point
-because more surface contact between molecules (more electrons)
- so more london forces between molecules
-more energy needed to overcome these london forces

Question 3

how does branching effect boiling point?

Answer 3

-more branching, lower boiling point
-less points of surface contact between molecules
-fewer london forces between molecules
-less energy needed to break weaker london forces

Question 4

why are alkanes relatively unreactive?

Answer 4

c-c and c-H sigma bonds are non-polar and strong covalent
-high bond enthalpy

Question 5

what happens when alkanes are burned with a limited supply of oxygen?

Answer 5

incomplete combustion
produces CO and H2O

Question 6

define radical

Answer 6

species with unpaired electrons

Question 7

what are the limitations of radical substitution?

Answer 7

-further substitution means mixture of haloalkanes produced
-may be reactions at different points in a carbon chain creating structural isomers

Question 8

how to avoid further substitution?

Answer 8

use an excess of alkane

Question 9

initiation formula

Answer 9

molecule with UV to 2x radicals

Question 10

propagation formula

Answer 10

radical + molecule makes radical + molecule

Question 11

termination formula

Answer 11

radical + radical makes a molecule

Question 12

what type of fission is initiation?

Answer 12

homolytic fission