DF - organic reactions *02 Flashcards
Complete combustion
When an organic compound is burnt completely in oxygen
-alkanes, cycloalkanes, alkenes, alcohols
produce carbon dioxide and water
very exothermic
- so make great fuels
equation for complete combustion of alkanes
CH4 (g) + 2O2 (g) –> CO2 (g) + H2O (g)
equation for complete combustion of cycloalkanes
C4H8 (g) + 6O2 (g) –> 4CO2 (g) + 4H2O (g)
equation for complete combustion of alkenes
C4H8 (g) + 6O2 (g) –> 4CO2 (g) + 4H2O (g)
equation for complete combustion of alcohols
CH3OH (l) + 1,1/2 O2 (g) –> CO2 (g) + 2H2O (g)
Incomplete combustion
when there is not enough oxygen organic compounds cannot burn completely
produce carbon monoxide and water
equation for incomplete combustion of alkanes
CH4 (g) + 1/2O2 (g) –> CO (g) + 2H2O
equation for incomplete combustion of cycloalkanes
C4H8 (g) + 4O2 (g) –> 4CO (g) + 4H2O (g)
equation for incomplete combustion of alkenes
C4H8 (g) + 4O2 (g) –> 4CO (g) + 4H2O (g)
equation for incomplete combustion of alcohols
CH3OH (l) + O2 (g) –> CO (g) + 2H2O (g)
addition reactions of alkenes - w/ bromine
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Electrophilic additon
1. the double bond repels the electrons in Br2, polarising Br-Br
2. heterolytic fission of Br2. The closer Br (the +ve one) gives up the bonding electrons to the other Br and sticks to the carbon atom
3. get a +vely charged carbonation intermediate, the Br- now zooms over…
4. …and bonds with the other C atom.
Forms: 1,2-dibromoethane
How do you test for an electrophilic addition with alkene and bromine?
If you add Cl- ions to an ethene and bromine mixture you will also get, CH2BrCH2Cl
this is evidence for electrophilic addition
- once ethene has reacted with bromine to form the carbocation, it can react with either another bromide ion or the chloride ion
addition reaction of alkenes - w/ hydrogen halides
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Electrophilic addition
1. the double bond repels the electrons in HBr, polarising H-Br
2. heterolytic fission of HBr. The H (the +ve one) gives up the bonding electrons to the Br and sticks to the carbon atom
3. get a +vely charged carbonation intermediate, the Br- now zooms over…
4. …and bonds with the other C atom.
Forms: 1-bromoethane (bromoalkanes)
alkene –> alkane ?
adding hydrogen to C=C bonds produces alkanes
needs nickel catalyst, 150degrees and high pressure
OR
needs a platinum catalyst, RTP
ethene –> ethane
ethene will react with hydrogen gas to produce ethane
- needs a catalyst (nickel), temp. 150c and high pressure
OR
- platinum catalyst at RTP