Basic Organic - Alkanes And Alkenes Flashcards
Alkene
C=C -ene
Alcohol
-OH hydroxy- /-ol
Haloalkane
-halogen chloro- bromo- iodo-
Aldehyde
-CHO -al
Ketone
-C(CO)C- -one
Carboxylic acid
-COOH oic acid
Ester
-COOC- oate
Acyl Chloride
-COCl -oyl chloride
Amine
-NH2 amino- -amine
Nitrile
-CN
Molecular formula
Number and type in molecule
Eg C2H6O
Empirical
Simplest whole number ratio
Eg C6H12O6= CH2O
Displayed formula
Relative positions drawing bonds between atoms
Structural formula
Arrangements of atoms in molecule
Eg CH3CH2CH2CH3
Structural isomers
Compounds with the same molecular formula but different structural formulae
Isomers w same function group- same function group different position
Isomers w different func groups eg ketones and aldehydes
Bond fission
Breaking covalent bonds
Homolytic or heterolytic fission
Homolytic fission
Each take one of the shared paired electrons forming radical
Cl• for example
Heterolytic fission
One of the bonded atoms take both electrons
Forms positive and negative ions
Addition reactions
Two reactants join together to form one product
Substitution
An atom or group of atoms are replaced
Elimination
Removal of a small molecule from larger forming 2 products
Alkanes
Used as fuel
CnH2n+2
Bonding in alkanes
Saturated hydrocarbons held together via single covalent bonds
Covalent bonds= sigma bonds result of 2 overlapping orbitals
Bond angle is 109.5
Boiling points in alkanes
Increase as chain length incr more electrons / greater sa therefore Greater London forces more energy required
Branched = lower bp fewer surface points of contact therefore London forces are weaker
Alkane reactions
Don’t react with most due to sigma bond strength and non polar molecules/bonds
Combustion forming CO2 and H2O
Reaction with halogens using UV light
Bro I nation of alkanes
- Initiation- bromine molecule broken via Homolytic fission v reactive Br radicals
- Propagation Br• reacts with a C-H bond forming •CH3 radical and HBr
•CH3 reacts with Br2 and forms a new Br• - Termination- Br• form Br2 or •CH3 forms C2H6 or forms CH3Br
Limitations of radical substitution
Further substitution takes place so difficult to form one organic compound
Can substitute until CBr4 or form monosubstiuted isomers by sub at different positions in the chain
Structure and bonding of Alkene
Unsaturated hydrocarbons
CnH2n
Sigma bonds and pi bonds
120 bond angle
Pi bonds
Overlap of 2p orbitals one from each carbon involved in double bond
Electron density is conc in this bond
Prevents carbon atoms rotating
Stereoisomers
E/z cis/trans
Same structural formula different arrangement of atoms in space
Cahn Ingold rules
If higher priority on the same side = z isomers
If higher priority on different = e isomers
Higher priority = higher atomic number
Reactivity of Alkene
React more readily due to the bond enthalpy of Oi bond is weaker so broken more readily
Addition reactions of Alkene
With hydrogen (nickel catalyst)
Halogens
Hydrogen halides
Steam (acid catalyst)
Electrophilic addition with Alkene a
Pi bond has high electron density which attracts electrophiles
HBr + Alkene pi bond attracted to positive hydrogen breaks
HBr breaks via heterolytic fission and Br- attracted to carbocation
Markownikoffs rule
Secondary carbocation forms the major product in contrast to the primary as it is more stable
Addition polymerisation
Monomer - Alkene
Polymer - poly(Alkene)
High temp and catalyst required
Disposing of waste polymers
Lack of reactivity of polymers makes it hard to dispose and are non biodegradable
Recycle- plastics chopped into flakes and reused
PVC recycling - solvents dissolve
Waste polymers as fuels
