Atomic orbital: In atomic theory and quantum mechanics, an atomic 

orbital is a mathematical function that

describes the wave-like behavior of either one electron or a pair of electrons in an atom. This function can be
used to calculate the probability of finding any electron of an atom in any specific region around the atom's
nucleus.
Types of Hybridisation
The following are the types of hybridisation:
1) Sp – Hybridisation
In such hybridisation one s- and one p-orbital are mixed to form two sp – hybrid orbitals, having a linear
structure with bond angle 180 degrees. For example in the formation of BeCl2, first “Be” atom comes in excited
state 2s12p1, then hybridized to form two sp – hybrid orbitals. These hybrid orbitals overlap with the two p-
orbitals of two chlorine atoms to form BeCl2
2) Sp2 – Hybridisation: In such hybridisation one s- and two p-orbitals are mixed form three sp2– hybrid
orbitals, having a planar triangular structure with bond angle 120 degrees.
3) Sp3 – Hybridisation
In such hybridisation one s- and three p-orbitals are mixed to form four sp3– hybrid orbitals having a tetrahedral
structure with bond angle 109 degrees 28′, that is, 109.5 degrees.

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 Alkanes
Alkanes are organic compounds that consist entirely of single-bonded carbon and hydrogen atoms and lack
any other functional groups. Alkanes have the general formula CnH2n+2 and can be subdivided into the
linear straight-chain alkanes, branched alkanes, and cycloalkanes. Alkanes are also saturated hydrocarbons.
Alkanes are the simplest and least reactive hydrocarbon species containing only carbons and hydrogens.
They are commercially very important, being the principal constituent of gasoline and lubricating oils. Due
to lack of unsaturation, alkanes are very less reactive and this laboratory conditions makes them a relatively
uninteresting, though very important component of organic chemistry.

Nomenclature of Alkanes
The name of alkanes end with suffix “-ane”. Whether or not the carbons are linked together end-to-end in a
ring (called cyclic alkanes or cycloalkanes) or whether they contain side chains and branches, the name of
every carbon-hydrogen chain that lacks any double bonds or functional groups will end with the suffix -ane.

Alkanes with unbranched carbon chains are simply named by the number of carbons in the chain. The first
four members of the series (in terms of number of carbon atoms) are named as follows:

CH4 = methane = one hydrogen-saturated carbon

C2H6 = ethane = two hydrogen-saturated carbons
C3H8 = propane = three hydrogen-saturated carbons
C4H10 = butane = four hydrogen-saturated carbons
Alkanes with five or more carbon atoms are named by adding the suffix -ane to the appropriate numerical
multiplier, except the terminal –a is removed from the basic numerical term. Hence, C 5H12 is called pentane,
C6H14 is called hexane, and C7H16 is called heptane and so forth.

Straight-chain alkanes are sometimes indicated by the prefix n- (for normal) to distinguish them from
branched-chain alkanes having the same number of carbon atoms. Although this is not strictly necessary, the
usage is still common in cases where there is an important difference in properties between the straight-
chain and branched-chain isomers: e.g. n-hexane is a neurotoxin while its branched-chain isomers are not.

IUPAC Nomenclature

Number of Hydrogen to Carbons

This equation describes the relationship between the number of hydrogen and carbon atoms in alkanes:

H = 2C + 2

Where "C" and "H" are used to represent the number of carbon and hydrogen atoms present in one molecule.
If C = 2, then H = 6.

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Many textbooks put this in the following format:

CnH2n+2

Where "Cn" and "H2n+2" represent the number of carbon and hydrogen atoms present in one molecule. If
Cn = 3, then H2n+2 = 2(3) + 2 = 8.

The following table contains the systematic names for the first twenty straight chain alkanes. It will be
important to familiarize yourself with these names because they will be the basis for naming many other
organic molecules throughout your course of study.

Name Molecular Condensed Name Molecular Condensed

Formula Structural Formula Structural formula
formula
Methane CH4 CH4 Undecane C11H24 CH3(CH2)9CH3
Ethane C2H6 CH3CH3 Dodecane C12H26 CH3(CH2)10CH3
Propane C3H8 CH3CH2CH3 Tridecane C13H28 CH3(CH2)11CH3
Butane C4H10 CH3(CH2)2CH3 Tetradecane C14H30 CH3(CH2)12CH3
Pentane C5H12 CH3(CH2)3CH3 Pentadecane C15H32 CH3(CH2)13CH3
Hexane C6H14 CH3(CH2)4CH3 Hexadecane C16H34 CH3(CH2)14CH3
Heptane C7H16 CH3(CH2)5CH3 Heptadecan C17H36 CH3(CH2)15CH3
e
Octane C8H18 CH3(CH2)6CH3 Octadecane C18H38 CH3(CH2)16CH3
Nonane C9H20 CH3(CH2)7CH3 Nonadecane C19H40 CH3(CH2)17CH3
Decane C10H22 CH3(CH2)8CH3 Eicosane C20H42 CH3(CH2)18CH3

Alkyl Groups
Alkanes can be described by the general formula CnH2n+2. An alkyl group is formed by removing one
hydrogen from the alkane chain and is described by the formula CnH2n+1. The removal of this hydrogen
results in a stem change from -ane to -yl. Take a look at the following examples.

The same concept can be applied to any of the straight chain alkane names provided in the table above.

Using Common Names with Branched Alkanes

Certain branched alkanes have common names that are still widely used today. These common names make
use of prefixes, such as iso-, sec-, tert-, and neo-. The prefix iso-, which stands for isomer, is commonly
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given to 2-methyl alkanes. In other words, if there is methyl group located on the second carbon of a carbon
chain, we can use the prefix iso-. The prefix will be placed in front of the alkane name that indicates
the total number of carbons. Examples:

Isopentane which is the same as 2-methylbutane

Isobutane which is the same as 2-methylpropane

To assign the prefixes sec-, which stands for secondary, and tert-, for tertiary, it is important that we first
learn how to classify carbon molecules. If a carbon is attached to only one other carbon, it is called
a primary carbon. If a carbon is attached to two other carbons, it is called a seconday carbon.
A tertiary carbon is attached to three other carbons and last, a quaternary carbon is attached to four other
carbons. Examples:

4-sec-butylheptane

4-tert-butyl-5-isopropylhexane (30d); if using this example, may want to move sec/tert after iso disc

The prefix neo- refers to a substituent whose second-to-last carbon of the chain is trisubstituted (has three
methyl groups attached to it). A neo-pentyl has five carbons total. Examples:

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 neopentane neoheptane

Alkoxy Groups

Alkoxides consist of an organic group bonded to a negatively charged oxygen atom. In the general form,
alkoxides are written as RO-, where R represents the organic substituent.

Three Principles of Naming

1. Choose the longest, most substituted carbon chain containing a functional group.
2. A carbon bonded to a functional group must have the lowest possible carbon number. If there are no
functional groups, then any substitute present must have the lowest possible number.
3. Take the alphabetical order into consideration; that is, after applying the first two rules given above, make
sure that your substitutes and/or functional groups are written in alphabetical order.

Physical Properties of Alkanes

1. Alkanes are non-polar compounds. The difference in the electronegativities of Carbon and Hydrogen is
almost non-existent; hence they have an almost complete absence of polarity.
2. Alkanes generally have relatively lower boiling points and melting points. This is because their atoms have
weak Van Der Waals force and so the atomic bonds break easily.
3. However, as the molecules get bigger the force gets stronger. So more complex alkane has higher boiling
and melting points.
4. They can exist as solids liquids and gases in their natural states. Unbranched alkanes usually are gases in
their natural state. The examples are methane, ethane etc. The alkanes bigger than hexadecane are all solids.
5. Also, they are completely insoluble in water, again due to the weak van der Waal forces.
6. However, they are soluble in organic solids. Here the van der Waal forces of alkane break and are replaced
by newer van der Waal forces.

Sp3 hybridization of Alkanes: According to modern orbital theory carbon has electronic configuration.
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  C (ground state) 1s2 2s2 2px1 2py1 2pz0
 C (excited state) 1s2 2s1 2px1 2py1 2pz1

One 2s and three 2p orbitals are arranged in space in such a way that their axes are directed towards the
corners of a regular tetrahedron. In the formation of a methane molecule, the sp 3 orbitals overlap with 1s
orbital of four hydrogen atoms to form four s-sp3 sigma bonds.

In ethane molecule, sp3 orbital of one carbon overlaps with sp 3 orbital of the other carbon, the remaining
three sp3 orbitals of each of the two carbons overlap with the 1s orbitals of H. atoms to form s-sp 3 sigma
bonds

Method of preparation of alkanes

1. Hydrogenation of Alkenes and alkynes
2. Reduction of alkyl halides
3. Decarboxylation of carboxylic acids
4. Hydrolysis of Grignard reagent
5. Action of sodium on Alkyl halides; Wurtz reaction.
6. Corey-house alkane synthesis
7. Electrolysis of salts of carboxylic acid; Kolbe’s method

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Hydrogenation of Alkenes and alkynes: Alkanes can be prepared by the catalytic hydrogenation of
unsaturated hydrocarbons in the presence of catalyst ‘Ni’ or ‘pt’ at 2000 to 3000C.

Reduction of alkyl halides: Alkyl halide undergo reduction with nascent hydrogen in presence of reducing
agent like Zn/HCl to form alkanes

Decarboxylation of carboxylic acid: when sodium salt of carboxylic acid is heated strongly with sodalime
(NaOH + CaO) to form sodium carbonate and alkane.

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Hydrolysis of Grignard reagents: Alkyl magnesium halides (Grignard reagent) are obtained by treating alkyl
halides with magnesium in anhydrous ether. When Grignard reagent is hydrolysed alkanes are generated.

Wurtz synthesis: Higher alkanes are produced by heating an alkyl halide with sodium metal in dry ether. Two
molecules of alkyl halide lose their halogen atoms as NaX. This net result is the joining of two alkyl group to
yield symmetrical alkane having even number of carbon atoms.

Corey-House alkane synthesis: An alkyl halide is first converted to lithium dialkylcopper and then treated
with an alkyl halide to give alkane.

Kolbe’s electrolysis method: Alkanes are formed, on electrolysis of concentrated aqueous solution of sodium
or potassium salt of saturated monocarboxylic acid.

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 Reactions of Alkanes
A. Substitution reaction
1. Halogenations
2. Nitration
3. Sulphonation
B. Thermal and catalytic reaction
1. Oxidation
2. Pyrrolysis (Cracking)
3. Isomerization
4. Aromatisation
Halogenation of Alkanes: Halogenation is the replacement of one or more hydrogen atoms in an organic
compound by a halogen (fluorine, chlorine, bromine or iodine), which appears to be a simple substitution
reaction in which a C-H bond is broken and a new C-X bond is formed. E.g. the chlorination of methane, shown
below, provides a simple example of this reaction.
CH4 + Cl2 + energy → CH3Cl + HCl
Since only two covalent bonds are broken (C-H & Cl-Cl) and two covalent bonds are formed (C-Cl & H-Cl),
this reaction seems to be an ideal case for mechanistic investigation and speculation. However, one
complication is that all the hydrogen atoms of an alkane may undergo substitution, resulting in a mixture of
products, as shown in the following unbalanced equation. The relative amounts of the various products depend
on the proportion of the two reactants used. In the case of methane, a large excess of the hydrocarbon favors
formation of methyl chloride as the chief product; whereas, an excess of chlorine favors formation of
chloroform and carbon tetrachloride.

Nitration: When alkane react with nitric acid at high temp (400°-500°) to form nitro alkane

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Sulphonation: This involves the substitution of a hydrogen atom of alkane with –SO3H. When pronged
reaction of alkane with fuming sulphuric acid to give alkanesulfonic acid.

Combustion (oxidation): Combustion of alkane gives carbon dioxide and water. The general equation for
the combustion of hydrogen is given below.

Pyrolysis (Cracking): The decomposition of a compound by heat is called pyrolysis. This process when
applied to alkane is known as cracking. Larger alkanes are broken into a mixture lower molecular weight
alkanes, alkenes and hydrogen

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 Isomerization: Normal alkanes are converted to their branched chain isomers in the presence of aluminium
chloride and HCl e.g. n-butane is converted into isobutane

Aromatatization: Alkanes containing 6 to 10 carbon atoms are converted into benzene and its homologues
at high temp and in the presence of a catalyst. e.g. n- hexane is passed over Cr2O3 supported over alumina
at 600°C to form benzene

Paraffin
1. Paraffin‟s, more commonly referred to as alkanes, are the chemical family of saturated hydrocarbons.
2. The general formula CnH2n+2, C being a carbon atom, H a hydrogen atom, and „n‟ an integer.
3. The paraffin‟s are major constituents of natural gas and petroleum.
4. Paraffin‟s containing fewer than 5 carbon atoms per molecule are usually gaseous at room temperature,
those having 5 to 15 carbon atoms are usually liquids, and the straight-chain paraffins having more than 15
carbon atoms per molecule are solids.
5. Branched-chain paraffin‟s have a much higher octane number rating than straight-chain paraffin‟s and,
therefore, are the more desirable constituents of gasoline.
6. The hydrocarbons are immiscible with water. All paraffin‟s are colourless.
7. Paraffin is a strong-smelling liquid which is used as a fuel in heaters, lamps, and engines.

Paraffin wax:
1. It is also known as American English paraffin, is a white wax obtained from petrol or coal. It is used to
make candles and in beauty treatments.
2. The term "wax" simply refers to saturated hydrocarbons that contain more than 16 carbon atoms in the
paraffin series (C16-C40) and are in solid state at room temperature. Chemically, natural waxes are defined as
long chain esters, monohydric (one hydroxyl group), or alcohols with long chain fatty acids. The majority of
the waxes present in crude oil are considered synthetic paraffin waxes with non-oxidized saturated alkanes.

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 Uses of Paraffin
1. Medicinal liquid paraffin, also known as paraffinum liquidum, is a very highly refined mineral oil used in
cosmetics and for medical purposes.
2. Liquid paraffin has many uses in the medical field. Because liquid paraffin passes through the body's
intestinal tract without being absorbed, it can be used as a laxative to limit the amount of water removed
from the stool and ease constipation.
3. Liquid paraffin is considered to have a limited usefulness as an occasional laxative.
4. Liquid paraffin will reveal that this common personal care ingredient is used in many skin products,
including creams, lotions, lip balm, soap, and even eczema ointments.
5. In burns treatment that involved covering the affected area with a combination of waxes and oils including
paraffin wax; this petroleum-derived substance created a barrier for the skin to heal and was seen as a very
effective treatment.
6. Paraffin wax were developed, the most popular of which was giving hot wax baths to patients suffering from
a variety of ailments, in particular rheumatism and joint pain. The wax would be used to soften the skin and
the intense heat would soothe the muscles and ready them for massage treatment.
7. White soft paraffin with liquid paraffin is used as a barrier cream by providing a layer of oil on the surface
of the skin to prevent water evaporating from the skin surface. It is an emollient, sometimes known as skin
lubricant. It is used to soothe, smooth and hydrate the skin.

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