Alkenes Flashcards
what general formula does alkenes fit?
alkenes are hydrocarbons that fit the general formula CnH2n
how do alkenes work?
they work like alkanes, except that they have one C=C double-bond in their carbon change
what is the formula for ethene?
C2H4
how many ‘n’ does ethene have?
2
what is the formula for propene?
C3H6
how many ‘n’ does propene have?
3
what is the formula for butene?
C4H8
how many ‘n’ does butene have?
4
what is the formula for pentene?
C5H10
how many ‘n’ does pentene have?
5
how do we know alkenes contain the C=C double bond?
the names of alkenes end in ‘-ene’
how is the double bond written in a structural formula?
’=’
e.g. CH2=CHCH2CH3
what are alkenes?
alkenes are a homologous series of organic molecules, like alkanes but slightly different - however they are still a family of molecules
what three key features do alkenes?
- similar chemical reactions
- trends in physical properties (e.g. boiling points, viscosity or colour)
- the same general formula
what are isomers?
- like alkanes, alkenes also have isomers
- but unlike alkanes, their isomers can differ in more than one way
how can isomers be different?
- different branching of the carbon chain
- different positions of the C=C in the carbon chain
why are alkenes referred to as unsaturated?
because they have a C=C double bond
why are alkenes referred to as saturated?
because they don’t have a C=C double bond
can alkenes combust in oxygen?
yes - to release energy (they can also incompletely combust)
what happens when alkenes react with bromine?
they break the C=C bond and add the bromine atoms in
what type of reaction is alkenes reacting with bromine?
an addition reaction - because you are adding the bromine atoms into the alkene
can alkene and bromine reaction happen without UV light?
yes - because alkenes are more reactive than alkanes
what state does bromine need to be in to react with alkenes?
with pure bromine liquid or bromine water (orange)
what colour does the mixture of bromine and alkenes turn?
from orange to colourless - because bromine is used up in the reaction
what is bromine and alkene reaction used to test for?
the C=C in unsaturated compounds
