All of Alkanes Explained in 10 Minutes

Alkanes are saturated class of

hydrocarbons which means that in this

case a single bond is present between

carbon atoms and we need to remember

that actually saturated compounds are

those compounds which only contain a

single bond present in them. First of

all we need to understand the general

formula of alkanes and it is CNH2N

plus2. Keep in mind here N represents

the total number of carbon atoms present

in alkan. To understand it deeply let's

apply this formula to a few examples. If

the number of carbon atoms in alkan is

equal to 1, it means that by applying

the formula we will get methane with the

formula CH4 and also you need to keep in

mind that methane is the simplest alkan.

Now if we apply this formula when n is

equal to 2, we will get C2H6

which is called ethane. Keep in mind

that by applying the same formula for

any number of carbon atoms, we can find

out how many hydrogens will be present

in each case. Now let's understand why

alkanes are also called paraffins. Here

we need to remember that paraffins is a

Latin word which is actually a

combination of two words and they are

pum meaning little and aphinis meaning

affinity which tells us that alkanes are

actually very less reactive. The main

reasons for the less reactivity of

alkanes are due to the non-reactivity of

the sigma bond present in alkanes. Now

let's move towards the nomenclature of

alkanes. To understand it deeply first

we need to learn some important rules.

The first and most important rule is

that we have to select the longest

possible carbon chain which will give

the parent name to the alkanes. To

understand the first rule, let's have a

look at the following structure. Since

the longest possible chain has five

carbons, we need to select it. Now, if

we move towards the second rule, it says

that if the parent chain has any branch

or substituent present on it, then

numbering will start from that side,

which gives the least number to the

branch attached. To understand it, let's

look at the following structure. In this

case, since the methyl group is present

on the second carbon from the left side,

we have to start numbering from left to

right and its name will be two methyl

pentane. Moving towards the third rule,

if branches are identical, we should use

prefixes such as try, tetra and so on.

But keep in mind if branches present on

the parent chain are different, we need

to follow alphabetical order. Which

means that if the parent chain has both

methyl and ethyl groups present as

branches or substituents then in this

case since ethel comes alphabetically

first before methyl we will write

ethylmethyl rather than methyl ethel

which follows alphabetical order. Now we

should move towards the preparation of

alkanes. First we will discuss the

preparation of alkanes from alkenes and

alkynes. Keep in mind that alkanes can

be prepared from the hydrogenation of

unsaturated hydrocarbons such as alkenes

and alkyes. Actually hydrogenation

refers to the addition of hydrogen and

in this case hydrogenation is done in

the presence of catalysts such as nickel

and platinum. If we look at the reaction

for the formation of alkanes by

hydrogenation of unsaturated

hydrocarbons. In this case ethine will

react with one mole of hydrogen which

will result in the breaking of the

carbonarbon double bond and will lead to

the formation of ethane. Now we should

move towards the warts reaction for the

preparation of alkanes. We need to

understand that this method is used to

prepare higher alkanes. In this case,

alkalhalides react with sodium and dry

ether to form alkanes. If we look at the

reaction, in this case, two molar

concentrations of methyl bromide will

react with two molar concentrations of

sodium to form one molar concentration

of ethane and two molar concentrations

of sodium bromide. Keep in mind that we

can also prepare alkanes from the

decarboxilation of caroxyic acids. In

this case, first we need to understand

that actually decarboxilation means the

removal of the caroxile group. And if we

remove the caroxile group, it will

result in the formation of alkan. Keep

in mind that this reaction happens when

the sodium salt of caroxyic acids reacts

with sodaline. If we look at the

balanced chemical reaction for the

formation of alkanes. In this case, one

mole of sodium acetate will react with

one mole of sodium to form one molar

concentration of methane and sodium

carbonate. Now we should move towards

reactions of alkanes. But keep in mind

that although alkanes are chemically

inert, they can still undergo some

reactions such as thermal or catalytic

reactions and substitution reactions. In

a complete combustion reaction of

methane, it will produce carbon dioxide

and two molar concentrations of water

molecules. But if an incomplete

combustion reaction takes place, it will

result in the formation of carbon

monoxide and water molecules. Now if we

move towards the catalytic oxidation of

methane it can change into formaldahhide

and formic acid. You need to keep in

mind that catalytic oxidation means the

addition of oxygen in the presence of a

suitable catalyst. During this reaction

in the first step methane will react

with a water molecule to form methanol.

Next in the second step methanol will be

converted into formaldahhide and finally

the oxidation of formaldahhide will

change it into formic acid. Now let's

move towards a very important reaction

of alkanes which is called the h

hallogenation of alcanes. This reaction

takes place in the presence of sunlight

and it follows a free radical mechanism.

Keep in mind that a free radical refers

to a highly reactive species with an

unpaired electron. Actually the free

radical mechanism takes place in three

steps which are initiation, propagation

and termination. In the first step

during initiation the formation of

radicals takes place. During the second

step propagation takes place. Remember

that propagation means the growth of

free radicals. In this step, radicals

will keep on growing during several

reactions and will result in the

formation of many valuable products. In

the last step, two radicals will react

with each other to form a stable

product. Here we need to understand that

termination refers to the ending or

termination of radicals. If we look at

the mechanism of the halogenation

reaction in this case during the

initiation process, a chlorine molecule

which means Cl2 will break down into two

chlorine radicals. In the second step

which is called propagation, these

chlorine radicals produced in the first

step will react with methane to produce

many valuable products by the successive

replacement of hydrogen atoms with

halogen. And after that finally in the

third step which is called termination

here a methyl radical will react with a

chlorine radical to produce methyl

chloride. As we can see that in this

case in the products no radical is

formed. So from here we can say that

during the halogenation process in the

third step radicals are terminated. Now

let's move towards isomeism phenomenon

in alkanes. Actually isomeism in alcanes

occurs when compounds have the same

molecular formula but different

structures. This means they contain the

same number of carbon and hydrogen atoms

but their atoms are arranged in

different ways. This type of isomeism in

alkanes is called structural isomeism

specifically chain isomeism. It happens

when the arrangement of carbon atoms in

the chain changes leading to different

physical and chemical properties. Now

let's understand chain isomeism in

alkanes. Alkanes can exist as straight

chain or branched chain isomers.

Straight chain isomers have all carbon

atoms connected in a continuous line

without any branches. And branched chain

isomers have at least one carbon atom

attached to the main chain as a side

group forming a branch. Even though

these isomers have the same molecular

formula, their properties such as

boiling points and densities can be

different because of their structural

differences. To understand it deeply,

let's take the example for the possible

isomers of butane. Remember that butane

is an example of an alkan that shows

chain isomeism. It has two isomers and

they are straight chain and branch

chain. In straight chain structure, all

four carbon atoms are connected in a

straight line. This isomer has a higher

boiling point than its branched

counterpart because its molecules can

pack closely together leading to

stronger intermolecular forces. But if

we look at the branched structure, three

carbon atoms form the main chain and the

fourth carbon is attached as a branch to

the second carbon. Because of its

branched structure, isobutane has a

lower boiling point than nb butane since

its molecules cannot pack as tightly as

straight chain molecules. One important

point we need to remember that as the

number of carbon atoms and alkanes

increases, the number of possible

isomers also increases. This is because

there are more ways to arrange the

carbon atoms in different chains. For

example, pentane has three isomers,

hexane has five isomers, and heptine has

nine isomers. This proves that the

number of possible isomers increases

rapidly with more carbon atoms, making

it more difficult to name and

differentiate them. Now, let's

understand physical properties of

alkanes. We need to understand that

alkanes have specific physical

properties that depend on their

molecular size and structure. These

properties include boiling points,

melting points, and solubility. Since

alkanes are non-polar molecules, their

behavior is mainly influenced by weak

London dispersion forces which are

temporary attractions between molecules.

First, let's have a look at melting and

boiling point. The boiling and melting

points of alkanes increase as the number

of carbon atoms increases. This happens

because larger alkanes have more

electrons and a greater surface area

leading to stronger London dispersion

forces between molecules. More energy is

needed to break these forces which

results in higher boiling and melting

points. For example, methane is a gas at

room temperature, but octane is a liquid

because it has stronger intermolecular

forces. Keep in mind that the structure

of an alkan also affects its boiling

point. Branched chain alkanes have lower

boiling points than straight chain

alkanes of the same molecular formula.

This is because branched molecules are

more compact and have less surface area

for intermolecular forces to act, making

it easier for them to evaporate. For

example, npentane has a higher boiling

point than its branched isomer

isopentane. Now let's discuss solubility

of alkanes. Alkanes are insoluble in

water because they are non-polar while

water is a polar solvent. The principle

like dissolves like explains why

non-polar substances do not mix with

polar substances. Water molecules

attract each other strongly through

hydrogen bonding and since alkanes

cannot form these bonds, they do not

dissolve in water. However, alkanes are

soluble in non-polar solvents like

benzene, ether, and chloroform. This is

because non-polar solvents have similar

weak intermolecular forces allowing

alkanes to dissolve easily. Now, let's

discuss some important use of alkanes.

Alcanes like methane, propane, and

butane are used as fuels in homes,

industries, and vehicles. Methane is

used in natural gas for cooking and

heating. Higher alkanes such as paraffin

wax are used in making candles,

polishes, and waterproof coatings. They

also serve as lubricants in machinery

and engines to reduce friction. Alkanes

like hexane and heptine are used as

solvents in industries for extracting

oils, cleaning, and dissolving non-polar

substances. They are also used in paints

and coatings. Alkanes are also the main

components of crude oil and are refined

into different fuels like petrol,

diesel, and kerosene. Alkanes also serve

as raw materials for making various

chemicals including alcohols, plastics,

and detergents. They undergo chemical

reactions like halogenation to produce

useful compounds for different

industries.