6 - Organic I Flashcards
homologous series definition
series of hydrocarbons with the same general formula
which organisation sets out how to name organic compounds
IUPAC
general formula for alkanes
Cn H2n+2
how to make fuel
1) crude oil goes to fractional distillation
2) cracking with 650°C and alumina catalyst
3) fractional distillation again
4) reforming
what does reforming mean
converting long chain hydrocarbons to branched or cyclic isomers to make them more easily combustible
what is reforming
chambers lined with solid catalysts like Pd, Pt or Rh
why are branched/cyclic molecules easier to combust
- can’t pack together easily
- weaker london forces
- more volatile
which pollutants are formed by combusting fuels
- CO from incomplete combustion
- Sulfur Oxides
- Nitrous Oxides
- unburned hydrocarbons
why are sulfur oxides bad
- So2 reacts with H2O in the air to form H2SO2, sulfurous acid
- weak acid but strong enough to harm plants and fish
why are nitrous oxides bad
- NO causes acid rain
- NO2 causes respiratory issues
why is carbon monoxide bad
binds with haemoglobin to form carboxyhaemoglobin which prevents binding of oxygen
what is a radical
a species with an unpaired electron
how is a radical formed
homolytic fission of a covalent bond
steps of alkane + halogen
1) initiation: Br - Br –> 2Br° using UV light
2) propagation: CH4 + Br° –> CH3° + HBr
CH3° + Br2 –> CH3Br + Br°
3) termination: 2CH3° –> C2H6
2Br° –> Br2
CH3° + Br° –> CH3Br
issues of halogen substitution
- low yield because you cannot prevent multiple substitutions, or prevent where substitutions take place
- a mixture of products is formed
general formula of alkenes
CnH2n
what bonding is present in alkenes and how does that affect their reactivity
- pi and sigma bonds
- pi bonds have side on overlap. This drags electrons at an angle, making it weaker and easier to break
why do alkenes have geometric isomers?
restricted rotation around the C=C bond
what is an electrophile
electron pair acceptor
reduction of alkenes
- add H2
- nickel catalyst
- 150°C
- saturates the alkene. used to make margarine from vegetable oils, to saturate the fats
oxidation of alkenes
- KMno4 (aq)
- H2SO4 (aq)
- makes diol
carbocation stability highest to lowest
3°
2°
1°
draw the mechanism for electrophilic addition of HBr to propene
check
draw the mechanism for ethene + steam
check
draw the mechanism for propene and bromine water
check
how are ions formed?
heterolytic bond fission of a covalent bond
how can you dispose of waste polymers
- recycle
- incinerate
- leave to decompose
- use as feedstock for cracking
how do scientists limit problems of polymer disposal?
- create biodegradable polymers
- remove toxic gases produced by incineration of polymers
what is a nucleophile
electron pair donor
what bonds do halogenoalkanes form
- london forces
- dipole dipole due to difference in electronegativity of halogens and carbon
what is SN1
- nucleophilic substitution 1
- 1 thing in rate equation
- tertiary halogenoalkanes
- forms carbocation
what is SN2
- nucleophilic substitution 2
- 2 things in rate equation
- primary halogenoalkanes
- forms intermediate
draw the mechanism for SN1
check
draw the mechanism for SN2
check
draw the mechanism for halogenoalkanes + KOH (aq)
check
mechanism for halogenoalkanes + AgNO3 (aq) in ethanol
- nucleophilic substitution
- NO3- is too stable so H2O is the nucleophile
- H20 is not negative so is a weak nucleophile so slow reaction
- silver halide formed so white ppt. seen
- check mechanism
mechanism for halogenoalkane + KCN (ethanol)
- nucleophilic substitution
- can’t be aqueous as OH- is a better nucleophile
- makes a nitrile, increasing the carbon chain by 1
- check mechanism
mechanism for halogenoalkane + NH3 (ethanol)
- nucleophilic substitution
- ammonia is a good nucleophile so it donates electrons to a H, forming NH4 +
- poor yield due to multiple substitutions
mechanism for halogenoalkane + KOH (ethanol)
- elimination
- makes alkene
- check mechanism
- OH- acts as a base
which halogenoalkane has the fastest hydrolysis rate and why
- iodoalkane
- longer and therefore weaker bonds
- lower activation energy
do tertiary or primary halogenoalkanes have faster hydrolysis rates and why
- tertiary have higher rate than primary
- tertiary always do SN1 which is faster
- in SN2 you release halogen and add nucleophile at the same time, so has higher activation energy
how can you compare rates of halogenoalkane hydrolysis
add aqueous silver nitrate in ethanol
