Alkanes Flashcards
What are structural isomers
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAMolecules with the same moleculer formula but different structural formula
What are the 3 ways to have a structural isomer to something
Chain isomers
Position isomers
Functional group isomers
What are chain isomers
Chain isomers have the same molecular formula but a different arrangement of the carbon skeleton. For example butane and 2 methyl propane have the same molecular formula of C4H10
What are position isomers
Have the functional group of the molecule in the different position of the carbon chain For example Propan-1-ol and Propan-2-ol
What are functional group isomers
Have the same molculer formula but the molecules have a different functional group. For example Hexene and Cyclohexane
What are the features of Alkanes
CH4 molecules have a tetrahedral shape because they contain 4 bonding pairs and 0 lone pairs
Carbon and hydrogen have very similar electronegativity values so the C-H bond is nonpolar
Features of alkanes (2)
CH4 is described as a non polar molecule
Induced dipole dipole bonds exist between the molecules of CH4
What are the physical properties of alkanes
The london forces are broken between the alkane molecules during boiling
The bonds between the atoms require too much more energy to overcome and are not broken during boiling
Why does the boiling point of alkanes decrease as branching between molecules increases
When there is more branching theres fewer points of contact so there are weaker induced dipole dipole forces so lower boiling points as less energy is required to overcome
How does a sigma bond form
By a head on overlap of the two atomic orbitals directly in a line between 2 bonded atoms
What are the products made with the complete combustion of alkanes
CO2 and H20
What are the products made with the incomplete combustion of alkanes
CO + H20
Carbon
Why is carbon monoxide dangerous
A toxic gaseous product that is odorless and colorless
What is a mechanism
A sequence of steps showing the path taken by electron in a reaction
How is a curly arrow used in reaction mechanisms
Used to describe the movement on an electron pair during a reaction
What is homolytic fission
The breaking of a covalent bond with one of the bonded electrons going to each atom forming 2 radicals
What are the alkanes reaction mechanism
Radical substitution
What is a radical
A species with an unpaired electron which are extremely reactive
What is the conversion used in radical substitution
Alkane—->Haloalkane
What condition is necessary for an alkane to react with chlorine or bromine
UV light
Why is the reaction described as a substitution reaction
1 hydrogen has been replaced with a halogen
What are the 3 steps used in radical substitution
Initiation
Propagation
Termination
What are the features of the initiation reaction
It creates radicals by breaking the bond between halogen by homolytic fission
It has a halogen to match the atom being substituted
NOT PART OF OVERRAL EQUATION
What is an example of an initiation reaction
Cl2—-> Cl*
* is radical
What happens during propagation
The radical “takes” an atom
A radical is conserved
There is a change in the overral equation
What is an example of propagation reactions
Cl+ CH3CH3—-> CH3CH2+HCL
CH3CH2+CL2–>CH3CH2CL+CL
CH3CH2* acts as an intermediate
Why are propagation reactions described as chain reactions
The Cl* radical is used in step 1 but regenerated in step 2
What happens during termination
2 radicals reacts to form stable molecules
What are examples of termination reactions
2Cl—> Cl2
Cl + CH3CH2* —> CH3CH2CL
CH3CH2+CH3CH2—>CH3CH2CH2CH3
What is the general formula of an alkane
Cn H2n+2
What happens to the boiling point as the alkane chain length increases
The boiling point increases because there is more surface area so there is a higher number of IDD interactions . Therefore more energy is required to overcome these interactions
What is complete combustion and what is the colour of the bunsen burner fame during it
Combustion that occurs with plentiful supply of air
The colour is blue
What is incomplete combustion
Limited supply of oxygen
What is the environmental impact of soot
Asthma
Cancer
Global dimming
