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Hydrocarbons and Fuels. Alkanes, Alkenes, and Alkyne, Halogen derivatives, Aromatic Hydrocarbons, Petrol, Alternative fuels,. Index. Carbon chemistry introduction. Alkanes and Alkenes. Alkynes. Halogen derivatives, CFC’s. Aromatic hydrocarbons. Fuels. - PowerPoint PPT Presentation
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Hydrocarbons and FuelsAlkanes, Alkenes, and Alkyne, Halogen derivatives, Aromatic
Hydrocarbons, Petrol, Alternative fuels,
IndexCarbon chemistry introduction
Alkanes and Alkenes
Alkynes
Halogen derivatives, CFC’s
Aromatic hydrocarbons
Fuels
Organic Chemistry, the Chemistry of Carbon
Originally chemical compounds were divided into 2 classes:Inorganic or Organic
Organic compounds were derived from living things. It was believed that they contained a ‘vital force’ and couldnot be made from inorganic compounds.
Carbon has the ability to CATENATE, formingcovalent bonds with its own atoms.
CCH H
Organic ChemistryOrganic chemistry is basically the study of compounds containing carbon
(with the exclusion of oxides and carbonates)
There are so many compounds containing carbon that a whole branch of chemistry is devoted to their study.Organic molecules may be as simple as methane,
CH4
or more complicated such as cholesterol
HO
Alkanes and AlkenesAlkane general formula
Alkene general formula
C n H 2n+2
C n H 2n
Structural formula
Name No C’s
MethEthPropButPentHexHeptOct
12345678
CH3CH2CH3 CH3 (CH2)2CH3
Straight Chain
CH3CH2CH3
Branched Chains and unsaturated
Condensed formula
C C C
H
H
H
H
H
H
H
HC C CHH
H
C HHH
H
H
Molecular formula C3H7
Naming Compounds of Carbon
1. Identify the longest chain2. Identify the ‘branches’ and name them.3. Number the carbon atoms on the longest chain, at the end giving
the lowest numbers for the branches.4. Write the branches in alphabetical order.5. If there are more branches with the same name
use di, tri etc
1. Identify the longest chain, that contains a double bond.2. Identify the ‘branches’ and name them.3. Number the carbon atoms on the longest chain, starting from
the end nearest the double bond. Pick the lowest number to describe the position of the double bond.
4. Write the branches in alphabetical order.5. If there are more branches with the same name
use di, tri etc
Alkanes
Alkenes
Naming Organic Compounds
H
H
C
H
H
C
CH2
H
C
H
H
C
H
H
C
H
H
C
CH2
CH3
C
H
H
CH3 CH2
CH3
1. Decide on the type of compound (ie. consider functional group)
2. Select the longest chain
3. Name the compound with the branched chains in alphabetical order.
alkane
10 C’s decane
7-ethyl-3-methyldecane
H
H
C
H
H
C
CH2
H
C
H
H
C
H
H
C
H
H
C
CH2
CH3
C
H
H
CH3 CH2
CH3
1. Decide on the type of compound (ie. consider functional group)
2. Select the longest chain
4. Name the compound with the branched chains in ascending order.
alkene
7 C’s heptene
hept-2-ene3. Number the C atoms so that the functional group has the lowest number
5,5-dimethylhept-2-ene
H
H
C
H
C2H5
C
H
H
C
H
CH3
CH3
C C
H
=
1. Decide on the type of compound (ie. consider functional group)
2. Select the longest chain
3. Name the compound with the branched chains and halogen in alphabetical order.
halogen (chloroalkane)
5 C’s pentane
3-chloro-2,2-dimethylpentane
H
H
C
H
CH3
C
H
Cl
H
C
H
H
CH3
C
H
C
H
STRUCTURAL ISOMERISM
There are two types1. Chain isomerism.Here the isomers have different arrangements of carbon atoms or different chains. For example there are two compounds with the molecular formula C4H10
H
H
C
H
H
H
H
C
H
HC
H
H
C H
H
C
H
H
C
CH3
H
H
H
C
butane 2-methylpropane
Here, you can see that 2-methylpropane has a side chain.
2. Position Isomerism. Here the isomers have the same carbon skeleton and functional group but the position of the functional group is different.
H
H
C
H
H
H
H
C
Cl
HC H
H
C
H
H
Cl
H
C
H
HC
1-chloropropane 2-chloropropane
H
H
C
H
H
H
H
C
OH
HC H
H
C
H
H
OH
H
C
H
HC
propan-1-ol
propan-2-ol
Reaction of AlkenesReaction with Hydrogen, hydrogenation, an addition reaction
Reaction with halogens,
+ H-H
Propene Propane
1,2 dibromopropanecolourless
C C CH
HH
H H
HC C CH
HH
H H
HHH
C C CH
HH
H H
H+ Br-Br
Orange/red
C C CH
HH
Br Br
HHH
Reaction with Hydrogen Halides
+ H-I
2 -iodopropane
1 -iodopropane
or
Normally the H from thehalide attaches to the C which already has themost hydrogen’s.
C C CH
HH
H H
H
C C C
H
H
H HH
H
H I
C C C
H
H
H HH
H
H I
Alkyne family CnH2n-2
C2H2
Addition reactions with H2 similar to alkenes.
but two stages are possible
Ethene
CaC2 + 2 H2O Ca(OH)2 + C2H2
Ni Catalyst 150 oC
C CH H
1st
2nd
CCH H
C C HH
C C HH +
+ H2
H2
Ethene
Ethane
H H
Halogen Derivatives
Halogenalkanes and Halogenalkenes
CHCl3
CCl4
CH3CCl3
CCl2=CCl2
CH2=CHClCF2=CF2
2-bromo-2-chloro-1,1,1-trifluorethane Halothane
CCl2F2
Lava lamps, non-polar alkanes and chloroalkanesmixed with polar water.
CCl2H2
Chloroform
Freon
Correcting fluid
Gortex, Teflon
Solvent for grease
Vinyl chloride
Paint Stripper
Degreasing agent
Halogen Derivatives, CFC’s
All CFC’s are very unreactive, are not flammable and not toxic. They are used as flame retardants.
CCl3F
CCl2F2
Chlorofluorocabons CFC’s
e.g. 1,1,1,2-tetrafluoroethane is used as a refrigerant.
Used as a blowing agent to make expanded foam
Recently Hydrofluorocarbons have replaced some CFC’s.
The first refrigerant, and in aerosols.
Ozone destruction O3
CFC’s are very stable, lasting for 100 years in theatmosphere. So over time, CFC’s can reach thestratosphere. Here, UV radiation attacks the CFC’sforming free radicals ( ) .
Free radicals react with O3, the reaction is complex, but one Cl free radical can break down 1 million O3 molecules.
ClO + O Cl + O2
Chlorofluorocabons CFC’s
CCl3F CCl2F + ClU.V.light
Cl + O3 ClO + O2
Aromatic Hydrocarbons
Aromatic carbon molecules contain the benzene ring.
BenzeneF.A. Kekule proposedthe original structure
as a result of a dream.
C6H6
Aliphatic carbon molecules contain the linear chains of carbon ring.
Aromatic carbon molecules containing the benzene ringand aliphatic chains are called Arenes.
The first structures are unstable and the electrons delocalise to form a much more stable structure.
CHCHCH
CHCH CH
Aromatic PropertiesCH3
CH3
CH3
CH3
CH3
CH=CH2
The benzene ring does not contain 3 double bonds, and so does not takepart easily in addition reactions. It is insoluble in water, being non-polar. It burns with a smoky flame as carbon is produced.
Aromatic compounds are used in dyes, herbicides, insecticides fungicides,
Methylbenzene (toluene)
Phenylethene (styrene)C6H5CH2CH
1,2 - dimethylbenzene
1,3 - dimethylbenzene
Aromatic compounds
COOH
OH
Cl
Cl
CHCCl3
Poly-aromatic hydrocarbons PAH
DDTdichlorodiphenyltrichloroethane
COOCH3
Aspirin2-ethanoyloxybenzenecarboxcyclic acid
NHCOCH3
Paracetamol4-hydroxyphenylethanamide
Petrol
Long chain Hydrocarbons tend to burn unevenly in a car engine, causing ‘knocking’. Branched chained hydrocarbons burn more evenly, so prevent’knocking’.
By products from the combustion of petrolare CO, CO2, NOx and unburned Hydrocarbons
The alkane 2,2,4,-trimethylpentane has good antiknock properties
This also has a high octane rating, 100.Straight chain hydrocarbons havea lower octane rating, heptane has anoctane number of 0. Benzene is 106.Unleaded petrol in UK has octane ratingof 95.
Petrol is a blend of different hydrocarbons and this can changedepending on the season. In the winter you would need a petrol which was more volatile. Companies change their blend 3 or 4 times a year.
CC
H
H
H
CH3
CH3
C
H
H
H
C
H
H
C
CH3
H
Petrol
Reforming, this is the process by which straight-chain alkanes undergo a chemical change to change them intonew, smoother burning compounds.High temperatures, pressures and a catalyst are used.Branched-alkanes, cycloalkanes and aromatic compoundsare produced.
Hydrocracking, this takes place at high temperaturesin the presence of hydrogen. Long straight chain hydrocarbons are changed into small branched chain andstraight chain alkanes.
Alternative Fuels, biofuelsBiogas Methane, produced by anaerobic respiration
Ethanol Produced by fermentation, octane rating of 111
MethanolA liquid, made from steam and methane. Octanerating of 114, also ‘clean’ burning. Toxic and corrosive
Hydrogen economy
The dream fuel, but needs electricity to make it.
Fuel Cells 2x more efficient than the internal combustion engine.Requires a source of hydrogen and oxygen.
Did you know?CFC’s where replaced by HFC’s which do not degrade theozone layer. However, they are greenhouse gases 1200x more powerful than CO2.A fridge contains 0.67kg of HFC’s, equivalent to 800 kgof CO2 . For this reason, some fridges now use HC’s, such as butane and propane. These are only 3 to 4x aspowerful a green house gas as CO2.
Did you know?Methane is 23x more powerful a greenhouse gas as CO2. Sewage methane can replace the use of natural gas for the generation of electrical power.
Green house emission
-5 -4 -3 -2 -1 0 1 2 3
Petrol
Diesel
Natural gas
Biogas
Fu
el
Carbon dioxide (kg) / litre of fuel burned
So why does burning biogas give a negative value?