Organic Chemistry:
Chemistry of Carbon Compounds
Why so many C compounds?
• Carbon atoms can bond with other carbon
atoms in chains, rings, and networks.
• Bonds are covalent.
Lewis Diagram of C
•
•C•
•
Carbon has 4 unpaired electrons.
It can form 4 covalent bonds.
Bonding Capacity of H, O, etc.
• H can form only 1 bond.
• O and S like to form 2 bonds.
• The halogens (F, Cl, Br, I) form only 1
bond.
• N and P form 3 bonds.
Properties of Covalent
Substances
•
•
•
•
•
•
(also called molecular substances)
Low melting & boiling points
Poor conductors of heat & electricity
May be soft or brittle
Generally nonpolar
Tend to dissolve in nonpolar solvents
React more slowly than ionic compounds
Chemical Formulas
• show kind & number of atoms.
CH4, CH3OH, CH3Cl, CH2Cl2
Structural Formulas
• Show kind & number of atoms.
• Also show bonding patterns and
approximate shapes of molecules.
• 2-D rep of 3-D object so structural formulas
aren’t totally realistic.
H
H–C–H
H
Structural Formulas
• – A single line represents one pair of
electrons (a single bond).
• = A double line represents two pairs of
electrons (a double bond).
•  A triple line represents three pairs of
electrons (a triple bond).
Shape
• The 4 unpaired electrons around the C
atom are located at the corners of a
tetrahedron.
• 109.5 apart.
Vocabulary Interlude
• Saturated: organic compounds containing
only single bonds.
• Unsaturated: organic compounds
containing one or more double or triple
bonds.
Vocabulary
• Hydrocarbons: organic compounds
containing only C and H.
• Homologous Series: a group of compounds
with related structures and properties. Each
member of the series differs from the one
before it by the same additional unit.
Condensed Structural Formula
• Shows kind & number of atoms
• Shows some structural information, but not
all the details.
H H H
H–C–C–C–H
H H H
Becomes
CH3CH2CH3
Alkanes
• Homologous series of saturated hydrocarbons.
• Release energy when burned.
CH4
H
H–C–H
H
C2H6
H H
H–C–C–H
H H
• Or CH3CH3
Alkanes or CnH2n+2
• C3H8
H H H
H–C–C–C–H
H H H
CH3CH2CH3
th
4
straight-chain alkane
C4H10
H H H H
H–C–C–C–C–H
H H H H
Or CH3CH2CH2CH3
Alkanes: base unit
CH4
CH3CH3
or C2H6
CH3CH2CH3
or C3H8
CH3CH2CH2CH3
or C4H10
CH3CH2CH2CH2CH3
or C5H12
Difference between each is CH2
Naming straight-chain Alkanes
• All alkanes have the suffix –ane.
• The prefix depends on the number
of C’s.
Prefix
Meth
Eth
Prop
But
Pent
Hex
Hept
Oct
Non
Dec
# of C atoms
1
2
3
4
5
6
7
8
9
10
Formula
Name
CH4
Methane
C2H6
Ethane
C3H8
Propane
C4H10
Butane
C5H12
Pentane
Properties of Alkanes
• Change systematically with number of C’s
• As the number of C’s increases, the boiling
point increases.
Branched-chain alkanes
• Beginning with butane, C4H10, there is more
than 1 way to arrange the atoms.
H
H–C–H
H H
H–C–C–C–H
H H H
Isomers
• Compounds with the same molecular formula
but different structural arrangement, and
therefore, different chemical properties.
• The more C atoms there are in the formula,
the more isomers there will be.  More
possible ways to arrange them.
Isomers
• Different structures, different properties.
• Isomers have different chemical and
physical properties.
Naming branched-chain alkanes
• Find the longest continuous chain or backbone of
C atoms. (Bends don’t count!)
• The base name is derived from the number of C’s
in the longest chain.
• Branches are named in the prefix. Branches are
also named by the number of C atoms. The
“branch” part of the name ends in “yl.”
• The location of the branch is shown by assigning
numbers to the C’s in the backbone. Number from
the end that gives the lowest number for the
branch.
• There may be more than 1 of the same type of
branch. Use di, tri, etc.
H
H–C–H
H H
H–C–C–C–H
H H H
Longest continuous chain has 3
carbon atoms – propane.
Branch has 1 carbon – methyl.
Branch has to be at C-2.
(Only give the number if
necessary.)
Methyl propane
C4H10
CH3CH(CH3)CH3
H
H–C–H
H–C–H
HH H
H–C–C–C–C–H
H H
H
H–C–H
H
Longest continuous chain has 6
carbon atoms. It’s a hexane.
Branch is 1 carbon long – methyl.
Branch is located at C-2.
2-methyl hexane
C7H16
CH3CH(CH3)CH2CH2CH2CH3
H
H–C–H
H H H
H– C–C–C–C–H
H
H
H–C–H H–C–H
H
H
Longest continuous chain has
6 carbon atoms: hexane
Branch is 1 carbon long: methyl
Branch is located at C-3
3-methyl hexane
C7H16
CH3CH2CH2CH(CH3)CH2CH3
CH3(CH2)2CH(CH3)CH2CH3
Alkenes
• Another homologous series of hydrocarbons.
• Each member contains one double covalent
bond between C atoms.
So alkenes are unsaturated.
• General formula = CnH2n
Naming Alkenes
• Names are derived from the name of the
alkane chain with the same number of C
atoms. Replace the –ane ending of the
alkane name with –ene.
1st member is C2H4, ethene.
H
H
C=C
H
H
Naming Alkenes
• Location of double bond is specified by
numbering C atoms in backbone. Give
bond the lowest possible number.
1-butene
H
HH
C=C–C–C–H
H H H H
2-butene
H H HH
H–C–C=C–C–H
H
H
C4H8
C4H8
CH2CHCH2CH3
CH3CHCHCH3
Naming Branched-Chain Alkenes
• Parent chain = longest chain that contains
the double bond.
• Also, position of double bond, not branches,
determines numbering of backbone.
• Give 1st C in bond lowest possible #.
Alkynes
•
Homologous series of unsaturated
hydrocarbons that contain one triple bond.
•
Each member contains one triple carboncarbon bond.
–
•
Alkynes are unsaturated.
General formula = CnH2n-2
Naming Alkynes
• Use the corresponding name from the
alkane series and change the –ane to –yne.
• If necessary, number the carbon atom at
which the triple bond occurs.
H–CC–H
C2H2
ethyne
CHCH
H
H–CC–C–H
H
C3H4
propyne
CHCCH3
HH
H–CC–C–C–H
HH
C4H6
1-butyne
CHCCH2CH3
H
H
H–C–CC–C–H
H
H
C4H6
2-butyne
CH3CCCH3
Organic Halide
• One or more of the hydrogen atoms in an alkane is
replaced with a halogen (F, Cl, Br, or I).
• Not hydrocarbons! Often called halocarbons.
• Use prefixes to specify substituent: fluoro, chloro,
bromo, iodo
• If more than one, use di, tri, etc. to specify # of
substituents.
• If necessary, give locations by numbering C-atoms
in backbone.
Naming Halides
CH3Cl
H
H–C–Cl
H
chloromethane
CH3CHFCH3
H H H
H–C–C–C–H
H F H
2-fluoropropane
C3H7F
Naming Halides
CH3CCl2CHClCH3
H Cl H H
H–C–C–C–C–H
H Cl Cl H
2,2,3-trichlorobutane
C4H7Cl3