Organic chemistry
Organic Compounds
• Organic Compounds - any
covalently bonded compound
containing carbon
• except carbonates CO3-, carbon
monoxide CO, carbon dioxide CO2
and acetates C2H3O2-
A. Organic Nomenclature
General Characteristics of
Organic Molecules
•Carbon always forms 4 covalent bonds
due to its hybridization of its s and p
orbitals
Structure of Organic
Molecules
Stabilities of Organic
Molecules
• Carbon forms very strong bonds
between H, O, N, and halogens.
• Carbon also forms strong bonds with itself.
• Therefore, C can form stable long chain or ring
structures.
• Bond strength increases from single to double to
triple bond.
• Bond length decreases in the same direction.
Hydrocarbons
• Hydrocarbons - Organic compounds
that contain only carbon & hydrogen
•Alkanes - contain only single covalent bonds
•Alkenes - contain one or more carbon - carbon
double bond
•Alkynes - contain one or more carbon-carbon triple
bond
Saturated & Unsaturated
Hydrocarbons
• Saturated hydrocarbons – contain only
single carbon-carbon bonds (alkanes)
• Unsaturated hydrocarbons – contain double
carbon-carbon bonds (alkenes)
or triple carbon-carbon (alkynes) bonds
Formulas
• Alkanes = CnH2n+2
• Alkenes = CnH2n
• Alkynes = CnH2n-2
Nomenclature
• Must memorize prefixes
• To name, look at the
formula for the
hydrocarbon
• Determine if it is an
alkane, alkene, or
alkyne
• Use the prefix for the
number of carbons
• Add ending (ane, ene,
yne)
Prefix
# of carbon
atoms
Meth-
1
Eth-
2
Prop-
3
But-
4
Pent-
5
Hex-
6
Hept-
7
Oct-
8
Non-
9
Dec-
10
Structural Formulas
• “Lazy” way to write the Hydrogens
• Instead of drawing the bonds, just state
how many hydrogens are attached
• NOTE: The bonds are between
CARBONS in a parent chain, and not
hydrogens!
Structural Formula
Lewis Structure
B.
the first ten alkanes
CH4 - methane
C2H6 - ethane
C3H8 - propane
C4Hl0 - butane
C5H12 - pentane
C6H14 - hexane
C7H16 - heptane
C8H18 - octane
C9H20 - nonane
C10H22 - decane
C.
the general formula is CnH 2n +2
1.
D.
where n stands for the number of carbons
Branched chain saturated hydrocarbons
1.
must name the longest straight chain
2.
number the straight chain so the branches
have the lowest number
3
list the branches in alphabetical order
e.g.
3-ethyl 2 methyl hexane
e.g.
3-ethyl 2 methyl hexane
Draw back bone for compound = in this case it is hexane
C
C-C-C-C-C-C
1
2
3
4
5
6
C
C
Number the carbons
Attach branch group
Make sure all C have 4 bonds
Designate the Location
Designate the location (number of the carbon on
the parent chain) for each attached group
2-methyl
1
2
3
4
2 - methyl pentane
5
Some Simple Alkanes
2-methylpentane
•2,2-dimethylbutane
3-ethylhexane
•2,3-dimethylbutane
E.
homologous series - differs from its neighbors
by only methylene group (CH2)
II. Types of formulas
A. Structural formulas - shows the
structure of a molecule
B. Condensed structural formulas
III.
cyclic hydrocarbon
A. named with the prefix cyclo
e.g. cyclohexane
Drawing and Naming Cycloalkanes
Cycloalkanes are represented by polygons. A
triangle represents cyclopropane, a square
represents cyclobutane, a pentagon represents
cyclopentane, and so on.
Alkenes and Alkynes
•
Unsaturated
– contain carbon-carbon double and triple bond
to which more hydrogen atoms can be added.
•
•
Alkenes: carbon-carbon double bonds
Alkynes: carbon-carbon triple bonds.
IV.
alkenes - doubled bonded hydrocarbons considered
to be unsaturated
a.
the double bond is located between two C
i.
ethene
H- C = C - H
I
H
b.
I
H
change the ane ending to ene
c.
in very large molecules you must give a number
where the double bond begins
e.g. 2- butene
d.
If there are more than one double bond the ene
is preceded by number of double bonds
1.3 pentadiene
V.
Alkynes - triple bonded hydrocarbons - also unsaturated
A.
the triple bond is located between the two C
1.
ethyne
H-C= C-H
B.
change the ane ending to yne
C.
must also indicate where the triple bond starts
e.g. 2-pentyne
Naming Alkenes and Alkynes
When the carbon chain has 4 or more C atoms,
number the chain to give the lowest number to the
double or triple bond.
1
2 3 4
CH2=CHCH2CH3
1-butene
CH3CH=CHCH3
2-butene

CH3C CCH3
2-butyne
Endings
• Alkanes (all C-C single bonded parent
chain) end in –ane
– Methane CH4
– Ethane C2H6
– Propane C3H8
• Attached carbon groups (substituents) end
in –yl
– Methyl CH3 – Ethyl CH3CH2– Propyl CH3CH2CH2 –
3-ethylpentane
VII alkyl halides
The attachment of a Halogen to a carbon group
(F, Cl, Br, I)
Chloro methane
dicloro, difluoro methane
2 – bromo butane
VII. alcohols - contain OH groups
A.
ethanol
B.
change the e to ol
C.
methane to methanol
VIII Ketones - contains double bonded oxygen
located anywhere but the end
A.
change to e to one
B.
propane to propanone
IX
X
XI
aldehydes - contains double bonded oxygen only
at the end
A.
change e to al
B.
ethane to ethanal
carboxylic Acid - contain a double bonded oxygen
and a hydroxylgroup
A.
change to e to oic acid
B.
ethane to ethanoic acid
ethers
A.
two alkyl groups attached to an oxygen
B. dimethyl ether
Aromatic Compounds and
Benzene
Aromatic compounds contain benzene.
Benzene, C6H6 , is represented as a six
carbon ring with 3 double bonds.
Two possible resonance structures can be
drawn to show benzene in this form.
H
H
H
H
H
H
H
H
H
H
H
H
When Benzene rings are attached to groups that have higher priorities – it is
known as a phenyl group (C6H5-)
Functional Groups
Functional Groups
Class
Alcohol
Functional group
R – OH
Ether
R — O — R’
Aldehyde
O
||
R—C—H
Ketone
O
||
R — C — R’
Carboxylic acid
O
||
— C — OH
Ester
O
||
R — C — O — R’
Amine
R’
|
R — N — R’’
CO2H
I
N
C
R
E
A
S
I
N
G
O
-CH
O
C
-OH
C=C
R-,C6H5-,Cl-, Br-, NO2
Isomers
• Straight chain alkanes: An alkane
that has all its carbons connected in a
row.
Branched chain alkanes: An alkane that has a
branching connection of carbons.
• Isomers: Compounds with same molecular formula
• but different structures.
F.
structural isomers
1.
same molecular formula put differ in
structural formula
2.
4 carbon alkane has two possible isomers
3.
C5H12 has 3 isomers
4.
C6H14 has 5 isomers
5.
C10H22 has 75
•Carbons in butane (C4H10) can be
arranged in two ways; four carbons in a
row (linear alkane) or a branching
(branched alkane). These two structures
are two isomers for butane.
•Different isomers are completely different
compounds. They have different structures,
different physical properties such as melting
point and boiling point, and may have different
physiological properties.
Learning Check
• Draw all possible structural isomers of C5H12
pentane
2-methlyl butane
2,2 – dimethyl propane
Example
•
•
•
•
•
Name C3H8
This falls under the equation CnH2n+2
Therefore it is an alkane
Since n=3 we will use the prefix prop
Since it is an alkane we will use the
ending ane
• propane
Example
• What is the formula for octene?
• Since the ending is -ene we know that it
is an alkene (CnH2n)
• Since the prefix is oct we know there
are 8 carbons
• C8H16
Example
•
•
•
•
Name C5H12
5 carbons = pent
CnH2n+2 = alkane (ane)
pentane