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21 (c) FUELS & Hydrocarbons Intro to Organic Chemistry
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Learning Outcomes
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Learning Outcomes
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Learning Outcomes
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Learning Outcomes
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Learning Outcomes
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Hydrocarbon A compound that contains only carbon and hydrogen
Main sources: Coal Natural gas (methane) Petroleum (crude oil) Fossil Fuels
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Let’s make a hydrocarbon!
6 Carbons 14 hydrogens 19 single bonds Do the carbons always have to be in a straight line? Do they all have the same shape? / take up the same space? Can the carbons be arranged in a ring/circle? Does the number of carbons present affect the number of hydrogens?
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Let’s make a hydrocarbon!
Can you draw it?
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Representing Hydrocarbons
3D Model Full structural formula Condensed structural formula (x2) Formula or CH3CH2CH2CH3 C4H10
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Representing Hydrocarbons
3D Model Full structural formula Condensed structural formula (x2) Formula or CH3CH2 (CH3)CH2CH3 C4H10
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b Vocabulary! Chain a series of carbons that are connected in a line Spine the longest chain of carbons in the molecule Branch when one carbon is bonded to more than 2 other carbons, it forms a branch
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Identify the SPINE and BRANCHES:
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Putting names to structures!
b Putting names to structures! Homologous Series Organic compounds are grouped into families with similar chemical properties called homologous series These families have different surnames!
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Organic Families- The Alkanes
b Organic Families- The Alkanes Organic Chemistry Family Tree Alkanes
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The Alkanes Saturated Names end in –ane (surname)
Pg 16 Names end in –ane (surname) Made up of carbon and hydrogen Only single carbon-carbon bonds Saturated
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First names Depend on the number of carbons: 1 C: meth- 2 C: eth-
3 C: prop- 4 C: but- 5 C: pent- 6 C: hex- 7C: hept- 8C: oct-
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The Alkanes Example: 3 carbons First name is prop-
All single bonds= ALKANE Surname is –ane Propane
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Rules for Naming Hydrocarbons
Choose the correct ending: -ane, -ene, or –yne Determine the longest carbon chain (spine). Where a double or triple bond is present, choose the longest chain that includes this bond. Assign numbers to each C of the parent chain. For alkenes and alkynes the first carbon of the multiple bond should have the smallest number. For alkanes the first branch (or first point of difference) should have the lowest #. Carbons in a multiple bond must be numbered consecutively. 4. Assign first name according to number of Cs (meth, eth, prop)
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Rules for Naming Hydrocarbons
Determine the correct name for each branch methyl, ethyl, propyl, etc. Attach the name of the branches alphabetically, along with their carbon position, to the front of the parent chain name. Separate numbers from letters with hyphens (e.g. 4-ethyl-2-methyldecane) When two or more branches are identical, use prefixes (di-, tri-, etc.) Numbers are separated with commas. When identical groups are on the same carbon, repeat the number of this carbon in the name. (e.g. 2,2-dimethylhexane)
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Name the following alkanes:
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Name the following alkanes:
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Question! Does the number of Carbons influence the number of hydrogens present in a molecule? naming
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Organic Chemistry Family Tree
Do these belong to the alkane family? Alkanes
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Organic Chemistry Family Tree
Alkenes Alkanes
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Meet the Alkenes Unsaturated Alkenes
b Meet the Alkenes Contain a DOUBLE carbon-carbon bond Unsaturated Names end in –ene (surname) Made up of carbon and hydrogen First names are the same as those for alkanes Alkenes
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The Alkenes Alkenes Pent-1-ene Pent-2-ene
b The Alkenes The position of the double bond is important! Alkenes Pent-1-ene Pent-2-ene
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The Alkenes NO! Pent-3-ene? Pent-2-ene
b The Alkenes The position of the double bond is important! NO! The same molecule! Pent-3-ene? Pent-2-ene
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The Alkenes But-1-ene Hex-3-ene 2-methylhex-3-ene 3-methyl pent-2-ene
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Name the following alkenes:
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Name the following alkenes:
C H C H 3 3 C H C C C H C H C H 3 2 C H C H 2 3
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b The Alkenes Is the ratio of carbons to hydrogens the same for alkenes as alkanes? Alkenes
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Cyclohexene- A Cyclic Alkene
b Cyclohexene- A Cyclic Alkene
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b Aliphatic Compound An organic compound that consists of open chains of carbon atoms and closed chain compounds (rings) that resemble them in chemical properties
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Organic Chemistry Family Tree
Do these belong to the alkane or alkene family? Alkenes Alkanes
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Organic Chemistry Family Tree
Alkenes Alkynes Alkanes
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The Alkynes Contain a TRIPLE carbon-carbon bond
Unsaturated Names end in –yne (surname) Made up of carbon and hydrogen First names are the same as those for alkanes and alkenes Alkynes
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Name these Alkynes Propyne Hex-3-yne 4-methylhex-2-ene
b Name these Alkynes Propyne Hex-3-yne 4-methylhex-2-ene 3-ethylhept-1-yne
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b The Alkynes Alkynes Is the ratio of carbons to hydrogens the same for alkynes as alkanes and alkenes?
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Test Yourself! Questions page 383
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Effect of bonding on the shape of hydrocarbons
Single bonded carbons Shape arises due to the repulsion of bonding electrons Alkanes
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Effect of bonding on the shape of hydrocarbons
Single bonded carbons Shape arises due to the repulsion of bonding electrons Alkanes
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Effect of bonding on the shape of hydrocarbons
Double/triple bonded carbons Alkenes/ alkynes
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Effect of bonding on the shape of hydrocarbons
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Effect of bonding on the shape of hydrocarbons
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Identify the tetrahedral and planar carbons in the following compounds:
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Benzene compounds- one ring to rule them all!
Molecular formula of benzene: C6H6 All carbons are arranged in a ring Can you figure out the structure of benzene?
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b Aromatic Compounds Compounds that contain a benzene ring structure in their molecules
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b Delocalised Benzene 6 electrons in the 3 double bonds of the benzene ring are ‘delocalised’ i.e: they are free to move around inside the whole hexagon
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b Aromatic Compounds Methyl benzene: Ethyl benzene:
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Structural Isomer A structural isomer is a molecule of a substance with the same molecular formula but a different structural formula E.g:C5H12
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Be careful!!
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How many isomers?C6H14
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An isomer is: Definition check!!!
A molecule of a substance with the same molecular formula but a different structural formula
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Definitions you need to know!
Hydrocarbon: a compound that contains carbon and hydrogen only Homologous series: a family of compounds with similar chemical properties Saturated Compound: one in which there are only single bonds between the atoms in the molecule Unsaturated Compound: one that contains one or more double or triple bonds
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Definitions you need to know!
Aliphatic Compound: An organic compound that consists of open chains of carbon atoms and closed chain compounds (rings) that resemble them in chemical properties Aromatic Compound: An organic compound that contains a benzene ring Structural Isomer: Compounds with the same molecular formula but different structural formulas
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To Prepare Ethene and Examine its Properties
Dehydration Reaction: Ethene is formed when a molecule of water is lost from ethanol Tetrahedral → planar carbon Aluminium oxide (Al2O3) is a dehydrating agent and acts as a catalyst → white powder
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To Prepare Ethene and Examine its Properties
Key Steps Glass wool holds the ethanol in place Aluminium oxide placed halfway along boiling tube and heated (do not heat ethanol) Allow bubbles to escape for a short time before using a boiling tube to collect gas → remove air from the system before collecting gas Gas collected through downward displacement of water → gas is less dense than water Discard first tube as it is probably mostly air
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To Prepare Ethene and Examine its Properties
SAFETY Keep gas from the flame- flammable! Raise apparatus and remove delivery tube from the water BEFORE removing the heat. →This prevents suck-back of water → As the vapour inside the boiling tube cools, a vacuum would be created and the water would be sucked back into the tube → The cold water could crack the boiling tube
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To Prepare Ethene and Examine its Properties
1. Physical Properties of Ethene Colourless gas with a sweetish smell Insoluble in water but soluble in cyclohexane (ch4 will explain why) 2. Combustion Burns with a yellow luminous flame When mixed with limewater after burning, it turns milky. → CO2 produced C2H O2 → 2CO H2O
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To Prepare Ethene and Examine its Properties
3. Test for Unsaturation Tests for Unsaturation Decolourises bromine water: red → colourless Decolourises acidified potassium purple → colourless permanganate (KMnO4)
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To Prepare Ethyne and Examine its Properties
CaC H2O → Ca(OH)2 + C2H2
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To Prepare Ethyne and Examine its Properties
Key Steps Water slowly added to calcium carbide → Fizzing observed → White solid formed (calcium hydroxide: Ca(OH)2) Flask gets warm: → Exothermic reaction (heat given out) Acidified copper sulphate solution → Removes impurities like hydrogen sulfide, phosphine and ammonia
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To Prepare Ethyne and Examine its Properties
1. Physical Properties of Ethyne Colourless gas with a sweetish flame Insoluble in water but soluble in cyclohexane (ch4 will explain why) 2. Combustion Burns with a luminous smoky flame Large amount of soot should form as a result of unburnt carbon 2C2H O2 → 4CO H2O
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To Prepare Ethyne and Examine its Properties
3. Test for Unsaturation 4. Major use of ethyne Ethyne also called acetylene Used in oxyacetylene welding and cutting (temps of 3000oC +) Tests for Unsaturation Decolourises bromine water: red → colourless Decolourises acidified potassium purple → colourless permanganate (KMnO4)
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