organics 2 Flashcards
Name the fractions and their uses
Refinery oil - cooking
Gasoline - cars
Kerosene - aircraft
Diesel - trains
Fuel oil - ships
Bitumen - road surfacing
alkane general formula
CnH (2n+2)
alkene formula
CnH2n
properties of short alkanes
volatile
low boiling point
flammable
properties of long alkanes
viscous
high boiling point
not flammable
Hydrocarbon + oxygen ->
-> carbon dioxide + water
what is cracking
thermal decomposition of of long chain alkane to short chain alkane and alkene
two type of cracking
catalytic and steam
which hydrocarbon are used for polymers
alkenes
why are alkenes used to form polymers
the double bonds can break to form two bonds = bond with adjacent molecules
why are alkenes unsaturated
double c bond
bromine water + solution of alkenes colour change
orange to colourless
list alkene addition reactions
alkene + oxygen
alkene + hydrogen
alkene + halogen
alkene + water
alkene and oxygen reaction
Alkenes can be involved in combustion reactions with oxygen. The outcome of these reactions is similar to when other hydrocarbons react with oxygen.
E.g. Ethene (C2H4) + oxygen (O2) → carbon monoxide (CO) + carbon (C) + water (H2O)
Because their combustion is incomplete, they burn with smoky flames.
alkene and hydrogen reaction
When a nickel catalyst is present, alkanes can be formed by combining hydrogen with an alkene.
E.g. Ethene (C2H4) + hydrogen (H2) → ethane (C2H6)
Adding hydrogen atoms across a carbon-carbon double bond is called hydrogenation.
alkene and water reaction
When a phosphoric acid catalyst is present, alcohols can be formed by reacting alkenes with steam.
E.g. Ethene (C2H4) + steam (H2O) → ethanol (C2H5OH)
alkene and halogen reaction
Alkenes, unlike alkanes, will react when shaken with bromine water. This causes the solution to change colour from orange-brown to colourless.
Alkenes react with bromine to produce dibromoalkanes.
E.g. ethene (C2H4) (colourless) + bromine (Br2) (orange-brown solution) → dibromoethane (CH2BrCH2Br) (colourless).
This can be used as a test to distinguish between alkenes and alkanes.
