4.1.1 Basic concepts & 4.1.2 Alkanes Flashcards
Hydrocarbon
contains H and C only
staturated
contains only C-C single bonds
unsaturated
contains at least one c=c double or triple bond
Aliphatic
contains C atoms joined in straight or branched chains - not a benzene ring
Alcytic
aliphatic molecule that contains C atoms joined in a ring but not a benzene ring
Aromatic
contains at least one benzene ring
Alkanes general formulae
CnH2n+2
how to draw skeletal formualae
dont draw carbons or H
ethane structural formulae
CH3CH3
how is a sigma bond formed
by overlapping orbitals between bonding atoms
can sigma bonds rotate
yes they can freely rotate
how is a Pi bond formed
formed by overlapping P orbitals above and below bonded atom
can Pi bonds rotate
No
what bonds make a double bond
Pi and sigma
what bond makes a single bond
Sigma
Bond fission definition
breaking covalent bonds
Homolytic fission definition
where covalent bond breaks and one of the bonding electrons moves to each atom forming 2 radicals
radical
species with at least one unpaired electron
a fish
hook arrow representing movement of 1 electron
Heterolytic fission
covalent bond breaks and both bonding electrons go to one of the atoms forming an anion and a cation
what does a curly arrow represent
movement of a pair of electrons when a covalent bond is broken or formed
mechanism definition
shows which covalent bonds are being broken and made
3 types of reactions
substitution
addition
elimination
substitution reaction
1 element is replaced by another in a molecule
addition reaction
where theres fewer products than reactants
elimination reaction
where theres one more product than reactants
what state are the first 4 alkanes
gases
what happens to the boiling point as the alkane gets bigger and why
increases as number of carbons increases due to there being more IMF that need more energy to overcome
strongest IMF in an alkane
London forces
do larger molecules have stronger or weaker london forces and why
stronger as they have more electrons
why do branched alkanes have lower melting points than straight chained alkanes
straight chained have more points of contact so there’s more london forces so more energy is required to overcome the IMF
what does complete combustion of an alkane form
carbon dioxide and water
what does incomplete combustion of alkane form
Carbon monoxide and water
Free Radical substitution steps
initiation
propagation
termination
chlorination of methane initiation step
Cl2 -> 2Cl*
chlorination of methane propagation step
Cl* + CH4 -> CH3* + HCl
CH3* + Cl2 -> CH3Cl + Cl*
what is the termination
add the radicals together to make Cl2
CH3Cl
C2H6
Limitations of free radical substitution
further substitutions can occur creating unwanted products from the radicals
