Ch. 22 Hydrocarbon Compounds

Ch. 22 Hydrocarbon Compounds

CH. 22 HYDROCARBON COMPOUNDS 22.1 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

Carbon atoms have 4 valence electrons Hydrogen atoms have 1 electron Carbon atoms will make 4 bonds Hydrogen atoms will only make one bond REPRESENTING HYDROCARBONS PROPERTIES OF HYDROCARBONS

Nonpolar molecules Will not mix with water Mix with other nonpolar molecules Tend to be gas or liquid (with low BP) at room temperature Combustible in presence of oxygen and heat

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 compound NAMING STRAIGHT CHAIN ALKANES IUPAC: International Union of Pure and Applied Chemistry Name ends with suffix

ane Prefix indicates the number of carbon atoms Note: the prefixes for the first 4 carbons are different than the prefixes used for inorganic compounds! 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 space

PRACTICE Draw complete structural formulas for straight chain alkanes with a) Three carbon atoms b) Four carbon atoms c) Seven carbon atoms Name each of them. PRACTICE

Draw the complete structural formula for a) Ethane b) Nonane c) Methane PRACTICE How many single bonds are there

in a propane molecule? How many single bonds are there in a butane molecule? 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 groups

Methyl Ethyl Propyl Butyl Pentyl, etc. PRACTICE Name this compound using the IUPAC system. *Notice that the longest chain is not written in a straight line.

PRACTICE Name the following compounds. PRACTICE Draw the structural formula for 3ethyl-2,4-dimethylhexane.

Draw the structural formula for 2,3-dimethylbutane. Draw the structural formula for 3,4-diethyl-2,5-dimethyloctane. 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 bond ALKENES Alkene: a hydrocarbon with at

least one double bond Naming Find 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 number Any substituents are named the same as with alkanes 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 prefix End the name in yne Name substituents as with alkanes PRACTICE Draw a complete structural formula for

each of the following hydrocarbon compounds. Ethane Ethene Ethyne Propane Propene Propyne 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 differ

STEREOISOMERS Stereoisomers: atoms are joined in same order, but in different arrangements in space Cis-trans isomers Enantiomers 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 bond 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 enantiomers The enantiomers have identical physical properties but can have different chemical reactions

PRACTICE 22.4 HYDROCARBON RINGS Cyclic Hydrocarbons AROMATIC HYDROCARBONS

Aromatic compounds contain a benzene ring Non-aromatic compounds are called aliphatic Benzene Resonance increases stability Two forms are extremes, the true

bonding is an average 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 group SUBSTITUTED AROMATIC COMPOUNDS With 2 substituent groups on a benzene ring numbering becomes part of the name

The different constitutional isomers have different properties 22.5 HYDROCARBONS FROM EARTHS CRUST Natural Gas

Source of low-mass alkanes 80% methane, 10% ethane, 4% propane, 2% butane 4% contains nitrogen, higher mass hydrocarbons, and helium Combustion requires O2 gas Methane burns with a hot, clean flame 22.5 HYDROCARBONS FROM EARTHS CRUST

Petroleum More complex compounds than in natural gas Mostly straight or branched-chain alkanes

Includes some aromatic compounds and sulfur-, oxygen-, or nitrogencontaining compounds Petroleum refining begins with distilling crude oil into fractions by boiling point BIOREMEDIATION Using oil-eating microbes (mostly bacteria) to clean up an oil-spill

Microbes digest crude oil into mostly CO2 and H2O Takes time to work Most effective along shorelines after other means of cleaning 22.5 HYDROCARBONS FROM EARTHS CRUST

Coal Classified by hardness and carbon content Mostly condensed aromatic hydrocarbons with high mass

Leaves more soot when burned Forms in multiple stages from pressure and heat over time Peat lignite bituminous anthracite

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