Homologous FamiliesHomologous Families

Properties & UsesProperties & Uses

Properties of Properties of AlkanesAlkanes Change Change systematicallysystematically with number of C’s with number of C’s

As the number of C’s increases, the As the number of C’s increases, the boiling pointboiling point increases. increases. The molecules get heavier & harder to The molecules get heavier & harder to

change into the gas phase.change into the gas phase. IMF (van der Waals/Dispersion) increasesIMF (van der Waals/Dispersion) increases

Properties of AlkanesProperties of Alkanes

Low ReactivityLow Reactivity Except readily undergo combustion – fuelsExcept readily undergo combustion – fuels Nonpolar – Don’t dissolve well in water.Nonpolar – Don’t dissolve well in water. Low melting pts & boiling pts.Low melting pts & boiling pts.

M.P. & B.P. increase with molecular massM.P. & B.P. increase with molecular mass High vapor pressuresHigh vapor pressures

Properties of Properties of Alkenes & AlkynesAlkenes & Alkynes

Nonpolar – low solubility in HNonpolar – low solubility in H22OO Fairly low M.P. & B.P.Fairly low M.P. & B.P. More reactiveMore reactive than alkanes than alkanes

Multiple Bond Multiple Bond sitesite of reactivity. of reactivity.

USES:USES: Ethene causes fruits to ripen; used as starting material in the Ethene causes fruits to ripen; used as starting material in the

synthesis of polyethylene.synthesis of polyethylene. Ethyne, or acetylene, is used as a fuel in welding torches.Ethyne, or acetylene, is used as a fuel in welding torches.

CycloalkanesCycloalkanes Ring structures with general formula:Ring structures with general formula:

CCnnHH2n2n

Naming CycloalkanesNaming Cycloalkanes Parent ChainParent Chain

Use the cycloalkane as the parent chain if it has a Use the cycloalkane as the parent chain if it has a great number of carbonsgreat number of carbons than any alkyl substituent. than any alkyl substituent.

Otherwise, use the alkyl chain as the parent and Otherwise, use the alkyl chain as the parent and cycloalkane as substituent.cycloalkane as substituent.

Numbering the CycloalkanesNumbering the Cycloalkanes Start with a substituted carbon so it has the lowest Start with a substituted carbon so it has the lowest

number and go in direction of lowest numbers.number and go in direction of lowest numbers. When two or more alkyl groups are present, number When two or more alkyl groups are present, number

according to alphabetical order.according to alphabetical order.

Aromatic HydrocarbonsAromatic Hydrocarbons Contain one or more benzene ringsContain one or more benzene rings Have strong, pungent odorsHave strong, pungent odors Produced by substitution on benzene ringProduced by substitution on benzene ring

Hydrocarbons from EarthHydrocarbons from Earth

Natural GasNatural Gas Composed of 80% methane, 10% ethane, 4% Composed of 80% methane, 10% ethane, 4%

propane, and 2% butanepropane, and 2% butane• Separated by Separated by liquefractionliquefraction

Readily undergo Readily undergo CombustionCombustion

• FrackingFracking utilizes water to extract oil and natural gas utilizes water to extract oil and natural gas from shale and tight-rock formations.from shale and tight-rock formations.

Creates Creates micro-fracturesmicro-fractures that are held together by the that are held together by the grains of sand.grains of sand.

Hydrocarbons from EarthHydrocarbons from Earth

PetroleumPetroleum Refining process starts with the distillation of Refining process starts with the distillation of

petroleum (crude oil) to divide it into petroleum (crude oil) to divide it into fractions fractions according to their according to their boiling pointboiling point..

• CrackingCracking is a controlled process by which is a controlled process by which hydrocarbons are hydrocarbons are broken down broken down into smaller, more into smaller, more useful molecules. useful molecules.

Needs high Needs high heatheat and a and a catalystcatalyst in the absence of oxygen. in the absence of oxygen. Used for Used for high yield high yield of gasoline and starting material for a of gasoline and starting material for a

variety of chemical synthesis reactions.variety of chemical synthesis reactions.

Fractional DistillationFractional Distillation

Fractional DistillationFractional Distillation Separates a mixture into a number of Separates a mixture into a number of different different

partsparts fractional fractional

Works because different substances in the Works because different substances in the mixture have mixture have different boiling pointsdifferent boiling points

Gases condense at the top, liquids in the middle, Gases condense at the top, liquids in the middle, solids settle to the bottomsolids settle to the bottom

Hydrocarbons with small molecules make better Hydrocarbons with small molecules make better fuels: fuels: volatilevolatile, , flow easilyflow easily and are and are easily ignitedeasily ignited

In the Laboratory…In the Laboratory…

http://www.chem-ilp.net/labTechniques/FractionalDistillationlAnimation.htm

Boiling Point and Carbon ChainBoiling Point and Carbon Chain

Hydrocarbons from EarthHydrocarbons from Earth

CoalCoal Formed from Formed from decayed plants decayed plants over millions of over millions of

years. First stage is the formation of years. First stage is the formation of peatpeat..

Consists largely of Consists largely of aromatic compounds aromatic compounds of of large molar mass.large molar mass.