Organic chemistry = chemistry of compounds containing CARBON
(exception: CO, CO2, CS2, carbonates, bicarbonates, cyanides)
examples:
ethanol (grain alcohol)
ethylene glycol (automobile antifreeze)
acetone (nail polish remover)
sucrose (table sugar)
glycerol tripalmitate (fat)
riboflavine (vitamin B2)
cysteine (amino acid)
chloroform (solvent)
C2H6O
C2H6O2
C3H6O
C12H22O11
C51H98O6
C17H22N4O6
C3H7NO2S
CHCl3
 composition of organic compounds: C, H, N, O, S, halogens
Structure of organic compounds is more complex than those of inorganic.
Physical properties
inorganic compounds
high melting points
most inorganic compounds are soluble in water
not soluble in organic liquids
most inorganic compounds conduct an electric current
organic compounds
low melting points
most organic compounds are insoluble in water
are soluble in organic liquids
don´t conduct electricity
A unique feature of CARBON:
1) ability to bind to other carbon atoms to give chains and rings of various lengths
(e.g. polyethylene plastic (PE) contains thousands of carbon atoms bonded together!)
2) tetravalence (covalence of four: it has four valence-shell electrons) makes possible the branching of chains and
the fusion of several rings
3) formation of quite stable single, double and triple bonds
4) formation of strong covalent bonds with many other atoms  existence of many different compounds
Classification of organic compounds
1) hydrocarbons
2) derivatives of hydrocarbons
1) hydrocarbons = compounds containing only two elements: C and H
- form the framework of all organic compounds
- two main classes:
1. aliphatic hydrocarbons (no benzene ring, see below)
a) saturated
- alkanes
- cycloalkanes
= CnH2n+2
= CnH2n
b) unsaturated - alkenes
- alkynes
= CnH2n
= CnH2n-2
2. aromatic hydrocarbons (one or more benzene ring)
- benzene and derivatives
- fused-ring aromatic hydrocarbons
2) derivatives of hydrocarbons = hydrocarbons containing one or more functional groups (C, H + other element(s))
functional group = the part of a molecule having a special arrangement of atoms that is largely responsible for the
chemical behavior of the parent molecule
 classes of compounds which react similarly (see later)
Important prefixes:
met1
et2
prop3
cyclo- = ring in a structure
but4
pent5
hex6
hept7
oct8
non9
dec10
Chemical formulas of organic compounds:
a) molecular formula - very brief one (information about the number of different atoms present in the molecule, no
information about the structure!)
b) full structural formula - all bonds are described
c) condensed structural formula - very useful, the best one !
example: ethanol (prefix et- = 2 carbons, an = derivative of an alkane, ending -ol = alcohol)
a) C2H6O
b)
H
H


HCCOH


H
H
c) CH3CH2OH
isomers = compounds that have the same molecular formula but differ in physical properties (because differ in the
structure)
example: C2H6O can be
a) ethanol (= alcohol)
or
b) dimethyl ether (= ether)
CH3  CH2  OH
CH3  O  CH3
important terms:
constitution = the type and the arrangement of both atoms and bonds in a molecule; it doesn´t describe spatial
arrangement
conformation = any of the large number of possible shapes of a molecule resulting from rotation of one part of the
molecule about a single bond
configuration = the spatial arrangement of atoms or groups in a molecule
saturated hydrocarbon = hydrocarbon in which there are no carbon-carbon double or triple bonds (all carbon atoms
are bonded to the maximum number of hydrogen atoms)
Valence of elemens in organic compounds
CARBON
NITROGEN
OXYGEN
SULPHUR
HYDROGEN
HALOGENS
remember:
always tetravalent
trivalent
bivalent
bivalent
monovalent
monovalent
* all carbon bonds are equivalent
* properties of organic compounds depend on their structure
* bonds in organic compounds are mostly covalent: nonpolar (C - C, C - H) or polar (bond between
C and halogen, N or O)
Types of bonds:
1) single  saturated hydrocarbons
2) multiple (double or triple)  unsaturated hydrocarbons
3) cumulative
4) conjugated
Types of reactions:
a) according to the external changes
1) substitution (replacement)
2) addition (multiplicity of chemical bond is lowered)
3) elimination (new multiple bond is often formed, small molecule is released)
4) rearrangement (of atoms and bonds in the molecule)
b) according to the bonding changes
1) bond splitting
- homolytic  formation of radicals
- heterolytic  formation of ions
2) formation of new bonds
important terms:
(free) radical = an atom or group of atoms with an unpaired valence electron
iont = charged particle (cation or anion)
reagent = a substance reacting with another substance (in a laboratory = compounds used in chemical analysis or
experiments)
electrophile = an ion or molecule that is electron deficient and can accept electrons (either positive ions, e.g. NO2+,
or molecules with a positive charge on a particular atom); they tend to attack negatively charged parts of a
molecule; electrophiles are often reducing agents and Lewis acids
nucleophile = an ion or molecule that can donate electrons (either negative ions, e.g. Cl-, or molecules that have
electron pairs, e.g. NH3); they tend to attack positively charged parts of a molecule; nucleophiles are often
oxidizing agents and Lewis bases
alkyl (group) = a group obtained by removing a hydrogen atom from an alkane, e.g. methyl group CH3 , derived
from methane CH4; ending -yl
aryl (group) = a group obtained by removing a hydrogen atom from an aromatic compound,
e.g. phenyl group C6H5 , derived from benzene C6H6
aromatic compounds
- contain one or more planar cycle
- number of delocalized electrons is 4n + 2 (n = 0, 1, 2, ...) = Hückel rule
- can form two or more resonance structures (= representation of the structure of a molecule by two or more
conventional formulae, e.g. benzene)
Nomenclature of organic compounds
1) trivial names - originally assigned to compounds on the basis of their origin or properties; the structure of the
compound cannot be derived from the trivial name
2) systematic names - express the structure of the compound (IUPAC)
a) substitutional principle - the name of the compound is derived from the name of the basic unbranched
hydrocarbon - MOST SUITABLE
b) radical-functional principle - the structure is characterized by a single typical group of atoms, to which the
rest of the molecule is attached
example:
number of C
number of
substituents
number of C
a) ethanol
b) ethyl alcohol
1
methmono
2
ethdi
11
undec-
3
proptri
4
buttetra
12
dodec-
5
pentpenta
6
hexhexa
13
tridec-
the other important prefixes:
n= normal, single unbranched chain
iso= carbon C2 of single unbranched chain binds methyl group
neo= carbon C2 of single unbranched chain binds two methyl groups
7
hepthepta
8
octocta
20
icosa-
9
nonnona
10
decdeca
Numbering of the hydrocarbon chain
1) find the longest unbranched chain containing the most main functional goups that can be indicated by specific
ending
2) or find the longest unbranched chain containing the most double bonds
(double bonds take precedence over triple bonds)
3) or find the longest unbranched chain
4) the main functional groups, multiple bonds and the other substituents must obtain the lowest-number locants as
possible
5) the root of the name of the compound is that of the hydrocarbon with the ending givin the degree of unsaturation
6) the ending expressing the presence of the main functional group is the last part of the compound name (the
presence of additional functional groups is expressed by the prefixes)
7) the root is preceded by prefixes indicating the presence of other hydrocarbon rests or non-hydrocarbon
components in the molecule: these prefixes are listed alphabetically
8) the presence of several identical components is indicated by the multiple prefixes: bi-, tri-, tetra, etc., for simple
substituents, and bis-, tris-, tetrakis-, etc., for complex substituents
9) each prefix and suffix is preceded by the locant giving the position on the parent hydrocarbon; the numbers are
separated from the rest of the word by a hyphen
10) the spatial arrangement is given by special affix placed prior to the
whole name of the compound
The cyclic main chain is selected so that number 1 corresponds to the main characteristic group and the numbers
increase in the direction yelding the lower locants for the multiple bonds and the other substituents.
If the cyclic skeleton contains a heteroatom (N, O, S), then it is prefered in the assignment of locants, even over the
main characterictic group.
The numbering of polycyclic skeletons is governed by special rules.
main functional group = group with the highest position in the „Table of functional groups“ ordering the groups
according to their „nomenclature importance“