Organic Chemistry Flashcards
Factors that affect the melting points of organic compounds
- molar mass
- branched + straight chain isomers
- functional groups
How does the molar mass affect the melting point of an organic compound
the greater the molar mass, the greater the strength of LDFs, which increases the melting point
How does the branching or straight chain isomers affect the melting point of an organic compound
the branches reduces the surface area of contact between molecules, which decreases the strengths of LDFs and thus decreases the melting point
How does the functional group affect the melting point of an organic compound
certain functional groups contain hydrogen bonding (alcohols, amides, carboxylic acids) and other dipole-dipole (ketones, aldehydes) and alkanes, alkenes have LDFs
Homolytic bond fission
a covalent bond between 2 atoms in a molecules breaks with each atom taking one electron from the bond
- forms radicals
Heterolytic bond fission
a covalent bond between 2 atoms in a molecule breaks with one atom taking both bonding electrons
- forms ions
What are the reactions with alkanes
combustion (complete&incomplete) and free radical substitution
Outline combustion with alkanes
complete combustion: in excess oxygen and carbon dioxide and water are produced
incomplete combustion: in lack of oxygen and carbon/carbon monoxide and water is produced
Outline free radical substitution
3 stages: initiation, propagation and termination
initiation: forming a radical
propagation: reacting a radical with non-radical
termination: forming a non-radical with 2 radical
What is the general equation for radical substitution
alkane + halogen → halogenoalkane + hydrogen halide
Why can alkenes undergo substation reactions and not alkanes
Molecules which contain π-bonds can undergo addition because they are unsaturated and since only the weaker π-bonds are broken rather than the strong sigma bonds addition reaction happens faster
- alkenes are more reactive than alkanes
Outline first step of free radical substitution
- Initiation (formation of radicals through homolytic bond fission + UV)
Br2 —> Br• + Br•
Outline second step of free radical substitution
- Propagation (reacting a radical with a non radical)
Br• + C2H6 —> HBr + C2H5•
C2H5• + Br2 —> C2H5Br + Br•
Outline last step of free radical substitution
- Termination (forming non-radicals from radicals)
Br• + Br• —> Br2
What is the general equation of free radical substitution
alkene + halogen –> halogenoalkane + hydrogen halide
What is the general formula of hydrogenation
alkene + hydrogen –> alkane
What are the conditions of hydrogenation
nickel catalyst + 150°C
What is the general formula of halogenation
alkene + halogen –> dihalogenoalkane
What is an example of halogenation
bromine test
What is the general formula of hydrohalogenation
alkene + hydrogen halide –> halogenoalkane
- weakest hydrogen halide bond reacts faster
What is the general formula of hydration
alkene + steam –> alcohol
What are the conditions for hydration
H2SO4 catalyst + heat + high pressure
What is the general formula of addition polymerisation
alkene –> polyalkane
List all the reactions of alkenes
- hydration
- hydrogenation
- combustion
- free radical substitution
- halogenation
- hydrohalogenation
- addition polymerasation
What are the different types of alcohol
- primary: the carbon to which the hydroxyl group is attached is attached to only 1 carbon
- secondary:the carbon to which the hydroxyl group is attached is attached to 2 carbons
- tertiary: the carbon to which the hydroxyl group is attached is attached to 3 carbons
Outline the oxidation of alcohols for primary alcohols
primary alcohols can form aldehydes
- further oxidised to carboxylic acids
What are the conditions for the oxidation of primary alcohols
- acidified potassium manganate/dichromate
- heat
Outline oxidation of secondary alcohols
they form ketones and water
Why do tertiary alcohols not oxidise
there no H atoms directly bonded to the C-OH
What is the general formula of esterification
alcohols + carboxylic acids –> ester + water