221 Hydrocarbons Organic Chemistry includes almost all carbon compounds Not limited to compounds found in living cells Hydrocarbon organic compound made of only hydrogen and carbon atoms hydrocarbons ID: 595471
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Ch. 22 Hydrocarbon CompoundsSlide2
22.1 Hydrocarbons
Organic Chemistry
includes almost all carbon compounds
Not limited to compounds found in living cellsHydrocarbon: organic compound made of only hydrogen and carbon atomsSlide3
hydrocarbons
Carbon atoms have 4 valence electrons
Hydrogen atoms have 1 electron
Carbon atoms will make 4 bonds
Hydrogen atoms will only make one bondSlide4
Representing hydrocarbonsSlide5
Properties of hydrocarbons
Nonpolar molecules
Will not mix with water
Mix with other nonpolar moleculesTend to be gas or liquid (with low BP) at room temperatureCombustible in presence
of oxygen and heatSlide6
Alkanes
Hydrocarbons with all single covalent bonds
Can be straight chain or branched chain (or ring structure)
Boiling Point and Melting Point increase with number of carbons in a straight chain compoundSlide7
Naming straight chain alkanes
IUPAC: International Union of Pure and Applied Chemistry
Name ends with suffix –
anePrefix indicates the number of carbon atoms
Note: the prefixes for the first 4 carbons are different than the prefixes used for inorganic compounds!Slide8
Drawing structural formulas
Start with the number of carbon atoms, linked by single bonds
Fill in as many hydrogen as necessary
Condensed structural formulas can be used
to save time and spaceSlide9
Practice
Draw complete structural formulas for straight chain alkanes with
Three carbon atoms
Four carbon atoms
Seven carbon atomsName each of them.Slide10
Practice
Draw the complete structural formula for
Ethane
Nonane
Methane Slide11
Practice
How many single bonds are there in a propane molecule?
How many single bonds are there in a butane molecule?Slide12
Branched-chain Hydrocarbons
One carbon atom is bonded to 3 or 4 other carbon atoms
Branches are named as substituent groups
The longest continuous carbon chain is the parent alkane (provides number of carbons for the name prefix)
Hydrocarbon substituents are called alkyl groupsMethylEthylPropylButylPentyl, etc.Slide13Slide14Slide15Slide16
Practice
Name this compound using the IUPAC system. *Notice that the longest chain is not written in a straight line.Slide17
PRactice
Name the following compounds.Slide18
Practice
Draw the structural formula for
3-ethyl-2,4-dimethylhexane.
Draw the structural formula for 2,3-dimethylbutane.
Draw the structural formula for 3,4-diethyl-2,5-dimethyloctane.Slide19
22.2 Unsaturated hydrocarbons
Saturated compound: contains the maximum number of hydrogen atoms per carbon atom (2n+2)
Unsaturated compound: contains at least one double or triple bondSlide20
Alkenes
Alkene: a hydrocarbon with at least one double bond
Naming
F
ind the longest continuous carbon chain that contains the double bond (this is the parent alkene)Name the parent alkene by the number prefix and end in –ene
Number the parent chain so that the double bond has the lowest possible numberAny substituents are named the same as with alkanesSlide21Slide22
Alkynes
Alkyne: a hydrocarbon with at least one triple bond
Naming
Number the parent chain so that the triple bond has the lowest possible number on the longest continuous chain
Name the parent chain with the number prefixEnd the name in –yneName substituents as with alkanesSlide23
Practice
Draw a complete structural formula for each of the following hydrocarbon compounds.
Ethane
Ethene
EthynePropanePropenePropyne Slide24
22.3 Isomers
Isomers have the same molecular formula but different structures
Constitutional (structural) isomers: same molecular formula but the atoms are arranged differently
Physical properties (BP, MP) differ
Chemical reactivities differSlide25
stereoisomers
Stereoisomers: atoms are joined in same order, but in different arrangements in space
Cis-trans
isomersEnantiomers Slide26
Cis-trans isomers
Cis-trans
isomers are most commonly found in compounds with double bonds (alkenes)
Cis configuration: similar groups are on the same side of the double bond
Trans configuration: similar groups are on opposite sides of the double bondSlide27
enantiomers
Occurs when a central atom (C) has four different atoms or groups attached
When this central atom is carbon, it is called an asymmetric carbon
Groups attached to an asymmetric carbon can form mirror images of each other
When these mirror images are not superimposable, the two forms are called enantiomersThe enantiomers have identical physical properties but can have different chemical reactionsSlide28Slide29
PracticeSlide30
22.4 Hydrocarbon Rings
Cyclic HydrocarbonsSlide31
Aromatic hydrocarbons
Aromatic compounds contain a benzene ring
Non-aromatic compounds are called aliphatic
BenzeneResonance increases stability
Two forms are extremes, the true bonding is an averageSlide32
Substituted aromatic compounds
A compound with substituents added to benzene ring use benzene as the parent hydrocarbon
When the benzene ring is a substituent, it is called a phenyl groupSlide33
Substituted aromatic compounds
With 2 substituent groups on a benzene ring numbering becomes part of the name
The different constitutional isomers have different propertiesSlide34
22.5 Hydrocarbons from earth’s crust
Natural Gas
Source of low-mass alkanes
80% methane, 10% ethane, 4% propane, 2% butane4% contains nitrogen, higher mass hydrocarbons, and helium
Combustion requires O2 gasMethane burns with a hot, clean flameSlide35
22.5 Hydrocarbons from earth’s crust
Petroleum
More complex compounds than in natural gas
Mostly straight or branched-chain alkanesIncludes some aromatic compounds and sulfur-, oxygen-, or nitrogen-containing compounds
Petroleum refining begins with distilling crude oil into fractions by boiling pointCracking breaks down larger hydrocarbons into smaller, more useful hydrocarbonsSlide36Slide37
bioremediation
Using oil-eating microbes (mostly bacteria) to clean up an oil-spill
Microbes digest crude oil into mostly CO
2 and H2O
Takes time to workMost effective along shorelines after other means of cleaningSlide38
22.5 Hydrocarbons from earth’s crust
Coal
Classified by hardness and carbon content
Mostly condensed aromatic hydrocarbons with high massLeaves more soot when burned
Forms in multiple stages from pressure and heat over timePeat lignite bituminous anthracite