Chapter I
Hydrocarbone Nomenclature and Reaction
Organic compounds are
compounds that could be
obtained from living organisms.
Inorganic compounds are
compounds that came from
nonliving sources.
 Introduction
 Organic Chemistry
The chemistry of the compounds of carbon
The human body is largely composed of organic compounds
Organic chemistry plays a central role in medicine, bioengineering
etc.
 Vitalism
It was originally thought organic compounds could be made only
by living things by intervention of a “vital force”
Fredrich Wöhler disproved vitalism in 1828 by making the organic
compound urea from the inorganic salt ammonium cyanate by
evaporation:
Chapter 1
3
 There are more than 10 million compounds listed in Chemical
Abstracts, and most of these are organic. Fortunately we can classify
them into a few dozen families. This classification is based on structural
entities which have a chemical reactivity that is roughly predictable - socalled functional groups.
functional groups are specific groups of atoms within molecules
that are responsible for the characteristic chemical reactions of
those molecules.
a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon
Alkanes
There are various subdivisions in the classification of hydrocarbons. One family of
hydrocarbons is called the alkanes, or sometimes paraffins (from the Latin parum
affinis, meaning "little affinity" and thus implying a lack of reactivity) or aliphatics
(from the Greek word aleiphar meaning "fat or oil"). They are also called saturated
hydrocarbons.
All alkanes that are open chain (not rings) have the general
formula CnH2n+2, where n is an integer.
Alkanes : CnH2n+2
Name
Methane
Ethane
Propane
Butane
Pentane
Hexane
Heptane
Octane
Nonane
Decane
Molecular Formula
CH4
C2H6
C3H8
C4H10
C5H12
C6H14
C7H16
C8H18
C9H20
C10H22
Classes of carbon and Hydrogen
•
•
•
•
•
Primary carbon : CH3-R
Secondary carbon : R-CH2-R
Tertiary carbon : (R)2-CH-R
Quaternary carbon: (R)4-C
Hydrogens are also referred
to as 1º, 2º or 3º according
to the type of carbon they
are bonded to.
Methane
Alkyl groups
• Alkyl groups are named by dropping the -ane suffix
of the alkanes and adding the suffix -yl. Methane
becomes a methyl group, ethane an ethyl group, etc.
Alkanes
Alkyl groups
‫‪ + ane‬األسم األساسي (المقطع االغريقي)‬
‫‪methane‬‬
‫‪meth + ane‬‬
IUPAC system of nomenclature
1.
Find and name the longest continuous carbon chain.
2.
Identify and name groups attached to this chain.
3.
Number the chain consecutively, starting at the end nearest a substituent
group.
4.
Designate the location of each substituent group by an appropriate number
and name.
5.
Assemble the name, listing groups in alphabetical order.
6.
The prefixes di, tri, tetra etc., used to designate several groups of the same
kind, are not considered when alphabetizing.
7.
Halogen substituent's are easily accommodated, using the names: fluoro (F), chloro (Cl-), bromo (Br-) and iodo (I-) also (-NH2) amino, (-NO2) nitro…
1-
Locate the longest continuous chain of carbon atoms; this chain determines the parent
name for the alkane.
Sometimes, you may need to go around corners and zigzag to find the longest (parent)
chain. (the parent chain is in blue):
•
CH3
If the parent chain for example has 6 carbon atoms, therefore, it is
a derivative of hexane and if it has 4 carbon atoms it is derivative of butane and so on .
H
H3C
CH
CH2
C
CH3CH2CH2CH2CHCH3
CH3CH2CH2CH2CHCH3
CH3
CH2
CH3
18
H2C
CH2
CH3
CH3
2- Number the longest chain beginning with the
end of the chain nearer to the substituent.
Substituent
6 5 4 3 2 1
CH3CH2CH2CH2CHCH3
Substituent
CH3
7 6 5 4
3
CH3CH2CH2CH2CHCH3
2 CH2
1CH3
19
3- Use the numbers obtained by application of rule 2 to
designate the location of the substituent group.
The parent name is placed last; the substituent
group, preceded by the number indicating its
location on the chain, is placed first.
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4. When two or more substituents are present, give each
corresponding to its location substituent a number
on the longest chain.
The substituent groups are listed alphabetically regardless of
their order of occurrence in the molecule.
21
5) When two or more substituents are identical, indicate this
by the use of the prefixes di-, tri-, tetra-, and so on.
22
6) When two substituents are present on the
same carbon, use the number twice.
CH3
H3CCH2
C
CH2CH2CH3
CH2
CH3
3-Ethyl-3-methylhexane
23
7. When two chains of equal length compete for selection as
the parent chain, choose the chain with the greater
number of substituents.
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8. When branching occurs at an equal
distance from both ends of the longest
chain, choose the name that gives the
lower number at the first point of
difference.
25
Drawing alkanes
CH3-CH2-CH2-CH2-CH3
n-Pentane
Physical Properties
• Methane, ethane, propane, and butane are gases;
pentane through hexadecane are liquids; the
homologues larger than hexadecane are solids.
• The boiling points of alkanes increase with
molecular weight.
• Branching reduces the boiling point, the more
branching the lower the boiling point.
• Alkanes are almost completely insoluble in water.
Reaction of alkanes
1-Halogenatio
2- combustion of alkanes
Cycloalkanes :
•Cycloalkanes are alkanes that have carbon atoms that
form a ring (called alicyclic compounds)
•Simple cycloalkanes are rings of (CH2)n, or CnH2n
Naming Cycloalkane
Count the number of carbon atoms in the ring and the number in the
largest substituent chain. If the number of carbon atoms in the ring is
equal to or greater than the number in the substituent, the compound is
named as an alkyl-substituted cycloalkane
For an alkyl- or halo-substituted cycloalkane, start at a point of
attachment as C1 and number the substituents on the ring so that the
second substituent has as low a number as possible.
Number the substituents and write the name
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Alkenes
Alkenes area class of HYDROCARBONS which contain only carbon and hydrogen. Two
other terms which describe alkenes are unsaturated and olefins.
UNSATURATED hydrocarbons contain either double or triple bonds. Since the compound is
unsaturated with respect to hydrogen atoms, the extra electrons are shared between 2 carbon
atoms forming double bonds in alkenes. Alkenes are also called OLEFINS because they
form oily liquids on reaction with chlorine gas.
All alkanes that are open chain (not rings) have the general formula CnH2n, where n
is an integer
HYBRIDISATION OF ORBITALS - ALKENES
+
3 SP2
P
Trigonal Planar
π
σ
Nomenclature of alkenes
1. The ene suffix indicates an alkenes or cycloalkenes.
2. The longest chain chosen for the root name must
include both carbon atoms of the double bond.
3. The root chain must be numbered from the end
nearest a double bond carbon atom. If the double
bond is in the center of the chain, the nearest
substituent rule is used to determine the end where
numbering starts.
4. In cycloalkenes the double bond carbons are assigned
ring locations C1 and C2. Which of the two is C1 may
be determined by the nearest substituent rule.
5. Substituent groups containing double bonds are:
38
H2C=CH– Vinyl group
H2C=CH–CH2– Allyl group
3-Propyl-2-heptene
2,3-DiMethyl cyclohexene
3-Chloro-4-ethyl cyclobutene
3-Methyl cyclohexene
Physical Properties of Alkenes
 Alkenes are non polar compounds.
 Insoluble in water.
 Soluble in non polar organic solvents.
 They are less dense than water.
 Range of physical states:
 ≤ 4 C's are gases
5 - 17 C's are liquids
 ≥ 18 C's are solids
 The alkenes has a boiling point which is a small number
of degrees lower than the corresponding alkanes.
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Reaction of alkene
1-Butene
n-Butane
1-Butene
1,2-DiChlorobutane
2-Butene
2-Butene
2-Clorobutane
2-Hydroxybutane
1-Butene
1-Butene
2-Chlorobutane
1-Chlorobutane
2-Hydroxybutane
shape: Linear
Nomenclature
1. Identify the longest continuous chain of carbon atoms that
contains the carbon-carbon triple bond. the - ane ending is
changed to – yne
2. Number the carbon atoms of the longest continuous chain,
starting at the end closest to the triple bond. .
3. The location and name of any substituent atom or group is
indicated.
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Reaction of alkyne
Alkenes and alkynes are generally more reactive than alkanes due to the electron
density available in their pi bonds
1. Addition of halogen
2-Addition of hydrogen
3. Addition of hydrogen halide
Reaction of alkyne
ketone
Acidity of alkyne
More acidity
Aromatic Compounds
Benzene
• Benzene (C6H6) is the simplest aromatic hydrocarbon (or arene).
• Benzene has four degrees of unsaturation, making it a highly unsaturated
hydrocarbon.
Benzene contains a planar 6-membered ring.
•All C-Cbond lengths are equal.
•Kekuléproposed two equilibrated structures
• Whereas unsaturated hydrocarbons such as alkenes, alkynes and dienes readily
undergo addition reactions, benzene does not.
Nomenclature of Benzene Derivatives
monosubstituted benzenes
Aside from the trivial names, we usually name monosubstituted benzenes
with benzene as the parent. The name of the substituent is prefixed to the
parent name.
For other monosubstituted benzenes, the presence of the substituent results
in a new parent name (Common name).
disubstituted benzene
A disubstituted benzene can be named with prefix numbers or by the ortho,
meta, para system, which shows the positional relationships of the two groups
to each other on the ring.
Reactions of Benzene
Aromatic substitution reactions
As described earlier benzene does not undergo addition reactions as do alkenes,
but substitution reactions of benzene are common. In these, a group or an atom
is substituted for a ring H – hence the reaction is referred to as an aromatic
substitution reaction.
Halogenation:
Treatment of benzene with bromine (Br2) in the presence of an iron(III) halide
catalyst yields bromobenzene, and Using chlorine gives chlorobenzene
Nitration:
If benzene is treated with concentrated nitric acid, with concentrated sulfuric
acid as the catalyst, nitrobenzene is formed.
Sulfonation:
Treatment of benzene with fuming sulfuric acid gives benzenesulfonic acid.
Alkylation:
When treated with a alkyl halides, denoted by R—X (see next topic) and aLewis acid
catalyst (AlX3 in this reaction), benzene is converted to an alkylbenzene. This reaction is
called a Friedel-Crafts alkylation after Charles Friedel, a French chemist, and James
Crafts, an American chemist, who developed this reaction in 1877. The term alkylation
means substitution by an alkyl group.
Acylation:
Friedel and Crafts developed a reaction similar to the alkylation reaction above. This type
of reaction is called a Friedel-Crafts acylation because an acyl group (see later) , not an
alkyl group, is substituted on the benzene ring. The symbol "R" is used commonly in organic
chemistry to denote an alkyl substituent.