Chapter 12-Alkanes Flashcards
(18 cards)
what is the general formula of alkanes
CnH2n+2
what is a sigma bond
a bonded formed from overlap of orbitals directly between bonding atoms, they are free to rotate
what shape and what is the bond angle of alkanes
tetrahedral with bond angle of 109.5 as they have 4 bonded pairs that repel equally
what happens to the boiling point as chain length increases
it increase because
- more electrons and points of contact between molecules
- the london forces strength increases
- more energy needed to break bonds
what happens to the boiling point as branching in isomers of alkanes increases
they decrease
- fewer points of contact
-london force strength decreases
-less energy needed to break
are alkanes soluble
they are non polar so do not dissolve only mix with nonpolsr solvents
are alkanes reactivity high or low
low
as the sigma bonds are hard to break and little difference in electronegativity
what is produced in a complete combustion of alkanes
CO2 and H2O
are alkanes good fuels
yes
what are the products of incomplete combustion
carbon monoxide and water
what are the 3 steps of radical substition
initiation
propagation
termination
what is initiation
UV radiation provides energy for homolytic fission of chlorine molecules producing highly reactive chlorine radicals
what is propagation
free radicals react with unreactive alkanes, breaking a C-H bond and forming a new radical and a halogenoalkane, while also regenerating the initial free radical.
why is radical substition desribe as a chain reaction
as the chlorine radicals regenrate
what is termination
this is when the reaction stops as their is no longer a supply of radicals
what are the limitations of radical substitions
it has a limitation for organic synthesis because of a large mixture of products can be formed
how are structural isomers of alkanes made
during substitions they can be put into different postions changing the strucutal formula
what do you put to indicate a radical
a .
