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Chemistry
Organic Chemistry
Alkenes
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General
formula =
C
n
H
2
n
C_nH_{2n}
C
n
H
2
n
Functional group:
C
=
C
bond
Ethene
(n=
2
)
Propene
(n=
3
)
But-1-ene
(n=
4
)
Cracking
:
Thermal decomposition reaction
, in which an
alkene
(and sometimes
hydrogen
) are produced from an
alkane.
Cracking always produces
short chain
compound with a
C
=
C
bond. e.g. Cracking of
ethane
will give
ethene
and
hydrogen
Butane
→
Ethane
+ Ethene:
C
4
H
10
−
>
C
2
H
6
+
C_4H_{10\ ->}\ C_2H_{6\ }+
C
4
H
10
−
>
C
2
H
6
+
C
2
H
4
\ C_2H_4
C
2
H
4
Hydrocarbons
:
Have
NO double bonds
Do not react with
aqueous bromine
, so the mixture stays
orange.
Unsaturated Hydrocarbons
:
Have
double bonds
React
with
aqueous bromine
, turning the mixture from
orange
to
colourless