Organic Chemical Reactions

How are organic liquids heated?

- flammable + low boiling point = can be combusted + can be evaporated and so open flame should NOT be used

- INSTEAD use a water bath

What does it mean to heat under reflux?

- heating a solution with an attached condenser which cools the vapour and allows it to condense back into the reaction flask

- used with reagents with low melting points to prevent them from escaping

alkane + halogen

- type: substitution

- name: halogenation (free radical halogenation)

- product: haloalkane + hydrogen halide

- reaction condition: in presence of UV light or heat

- slow reaction as alkanes are unreactive

haloalkane + NaOH (aq) or KOH (aq)

- type: substitution

- name: hydrolysis

- product: alcohol + sodium halide

- reaction conditions: heat under reflux in dilute alkali solution

- faster reaction due to added polarity

alkene + hydrogen

- type: addition

- name: hydrogenation

- products: alkane

- reaction condition: alkene dissolved in an organic solvent with a Pt, Pd or Ni catalyst in a hydrogen atmosphere

- addition reactions are faster than substitution reactions

alkene + halogen

- type: addition

- name: halogenation

- products: haloalkane

- rapid decolorisation of bromine by an alkene at room temperature is used to distinguish an alkene from an alkane

alkene + hydrogen halide

- type: addition

- name: hydrohalogenation

- products: haloalkane

- reaction conditions: no water may be present

alkene + water (steam)

- type: addition

- name: hydration

- products: alcohol

- reaction condition: steam and a suitable acid catalyst eg. H3PO4 or H2SO4

haloalkane to alkene + hydrogen halide

- type: elimination

- name: dehydrohalogenation

- reaction conditions: hot concentrated solution of NaOH or KOH in an ethanol solvent i.e in absence of water (amount of water produced in the second reaction is insufficient to cause hydrolysis)

alcohol to alkene + water (steam)

- type: elimination

- name: dehydration

- reaction condition: acid catalysed dehydration - heating of alcohol with an excess of concentrated H2SO4 or H3PO4

alkane to alkane + alkene

- type: elimination

- name: cracking - breaking up large hydrocarbons into smaller and more useful hydrocarbon

- thermal cracking: high pressure, high temperature, no catalyst

- catalytic cracking: low pressure, low temperature, catalyst

alcohol + carboxylic acid

- type: condensation

- name: esterification

- products: ester + water

- reaction conditions: gentle heating and acid catalyst eg. H2SO4

Alkanes/alkene/alcohol + oxygen

- type: combustion

- products: H2O and CO2

-exothermic