• Organic chemistry is a branch of chemistry that studies compound
based on carbon.
• In particular it deals with hydrocarbons rather than metal carbonates or
• It was once thought that organic molecules could only be made by
living things and not in the lab, hence the name.
• Hydrocarbons are compounds that contain mostly H and C. Other
common elements are oxygen, nitrogen and the halogens.
• Biochemistry can be thought of as a specialized branch of organic
• Hydrocarbons are a major source of energy in fuels and foods
(petroleum, coal, natural gas, protein, carbohydrates, fats) and
are the basis of drugs, materials (fabric, plastic), detergents, dy
es and explosives.
• Carbon is in group 4 and always forms covalent bonds. As it
has 4 valence electrons it will form 4 covalent bonds to
complete its valence shell.
• In organic molecules, oxygen will always form 2 covalent
bonds, hydrogen 1 bond, halogens 1 bond and nitrogen 3
• Carbon can form single and multiple bonds to
other carbons which result in different
• When carbon forms bonds to other elements
these make the compounds behave in certain
ways. These groups of atoms are called
FUNCTIONAL GROUPS and determine the
physical and chemical properties of an organic
Introduction to Hydrocarbons
• The simplest class of organic molecules is the
• There are four major classes of hydrocarbons: alkanes,
alkenes, alkynes, and aromatics.
Alkanes contain only single bonds.
• These compounds are also called saturated hydrocarbons
because they have the largest possible number of hydrogen
atoms per carbon.
• Example: ethane (C2H6).
Alkenes contain at least one carbon-carbon double bond.
• They are also called olefins.
• Example: ethene (C2H4).
Introduction to Hydrocarbons
• Alkynes contain a carbon-carbon triple bond.
• Example: EThyne (C2H2)
• Aromatic hydrocarbons have carbon atoms
connected in a planar ring structure.
• The best known example is benzene (C6H6).
• Alkenes, alkynes and aromatic hydrocarbons are
all examples of unsaturated hydrocarbons.
Names and Boiling points of alkanes
• The name of the alkane varies according to the number of C atoms present in
• A series of organic compoun
ds with the same general for
mula, but that vary by a sin
gle –CH2 atom
• Ex. Methane, Ethane, Propan
• We can make a table of members of a homologous series
of straight-chain alkanes.
• Successive members differ by one CH2 unit.
• The names each end in -ane.
• The prefix assigned indicates the number of carbon atoms.
• Example: CH4 is the alkane with a single carbon atom; it is
• The next member of the series is C2H6, with two carbon
atoms; it is called ethane.
• The formulas for alkanes may be written in a notation called
condensed structural formula.
• This notation shows which atoms are bonded to one another
but does not require that we draw in all of the bonds.
• Notice that each carbon in an alkane has four single bonds.
• Organic compounds can be thought of as a carbon and hydrogen c
hain attached to one or more functional group.
• Carbon can form long chains that have the same functional group(s
) and only differ by the number of carbons and hydrogen's present.
• This means the mass and properties vary in a regular and predict
• We call a group of compounds like this a HOMO-LOGOUS
• CH3OH, C2H5OH, C3H7OH, C4H9OH
• The General formula is CnH2n+1OH
Homologous series can be thought of as families of
organic compounds where:
• Successive compounds differ by a -CH2- unit.
• The compounds all have a general formula ex.
• They have similar chemical properties.
• Physical properties change in a regular manner
– as mass changes so do Vander Waals forces
and sometimes the polarity of the molecules.
HOMOLOGOUS SERIES: PROPERTIES
Alkane Boiling Point
Methane, CH4 -164
Ethane, C2H6 -89
Propane, C3H8 -42
Butane, C4H10 -0.5
Pentane, C5H12 36
Hexane, C6H14 69
Heptane, C7H16 98
Octane, C8H18 125
• Note the trend in b.p. is p
redictable due to increase
in Vander Waals’ forces
with mass but it is not line
ar – the increase in chain
length is proportionally
greater for the small
• Other physical properties
that vary predictably are
density and viscosity.
• With organic compounds it’s important to know
the difference between empirical, molecular,
structural and full structural formulas.
• Empirical: simplest ratio of atoms ex. CH3 for
• Molecular: actual number of atoms ex. C2H6
• Structural (condensed): shows overall structure
in one line ex. CH3CH2CH2COOH
• Full structural (displayed): shows every bond
and atom ex.
• Skeletal Formula
• A group of CnH2n+1 can be represented by R.
• So an alcohol can be represented by R-OH.
• Benzene (C6H6) can be represented by:
• Compounds containing benzene are known a
s the aromatic compounds.
• Nomenclature means naming and there are IUPAC rules
for naming organic compounds.
• The number of carbons determines the start of the name
Number of C atoms Stem Side Chain
1 meth methyl
2 eth ethyl
3 prop propyl
4 but butyl
5 pent pentyl
6 hex hexyl
Benzene ring benz phenyl
• Rule 1: Determine the longest continuous chain t
hat provides the root name.
• Rule 2: If alkyl substituents are present as branc
hed chains the name for the branch will b deter
mined by the no. of carbon atoms the suffix will c
hange from ‘–ane’ to ‘ –yl.’
• Rule 3: when no. the longest carbon chain the p
osition of any substituent must be lower .
• When there are several different substituents arr
ange them in alphabetical order prior to root na
• Rule 5: Use a comma to separate numbers.
• Rule 6: Use a hyphen to separate the no. an
• Rule 7: The no. of multiple substituents are
shown by di, tri, tetra, pent prefixes.
• Rule 8: Successive words are merged in on
Prefixes for side chains
Side chain Prefix in IUPAC name Example
-CH3 Methyl- 2-methylpropane
-C2H5 Ethyl- 3 ethylpentane
-C3H7 Propyl- 4-propylheptane
-F,-Cl, -Br, -I Fluoro-, chloro-, bromo-
-NH2 Amino- 2-aminoethanoic acid
• Alkanes contain hydrogen, carbon and all bonds
• They follow the formula CnH2n+2 for ex.
• CH4 is methane
• CH3-CH3 is called ethane
• CH3-CH2-CH3 is propane
• CH3CH2CH2CH3 is butane
• Alkenes also contain only C and H but contain at
least 1 double bond.
• The formula is CnH2n.
• The start of the name denotes the number of car
bons followed by a number to show which carbo
n the double bond is on followed by the ending
• CH2=CH-CH2-CH3 is but-1-ene.
• CH3-CH=CH-CH3 is but-2-ene.
ALKENES, ALKYNES, SATURATION
• Alkynes contain a C=C triple bond.
• Alkanes are SATURATED as they only
have single bonds.
• Alkenes and alkynes are UNSATURATED
as they contain multiple bonds. These
bonds are stronger and mean that the
molecules can react more.
• Alkenes are very important in the
petrochemical industry as they are the
starting place to make many other
Ester Functional group
• When the alkyl group of alcohol has replaced the
H of carboxylic acid.
C2H5COOH + HOCH3 → C2H5COOCH3
CH3CH2CH2COOC2H5 Name it ?
Amide Functional group
They are acid derivatives when the –OH of acid is
replaced by –NH2
Propanamide N-methylpropanamide N,N-dimethylpropanamide
Primary amine Sec. Amine Tert. Amine
AMine functional group
• When H atom of ammonia are replaced by
alkyl group then amines are formed.
NH3 -H +CH3 NH2CH3