All of HYDROCARBONS Explained in 8 Minutes

Hydrocarbons are compounds made up of

only carbon and hydrogen. For example,

butane is a hydrocarbon, but a similar

compound called butinol is not because

it also contains an oxygen atom.

Hydrocarbons can be classified into two

main categories, alifhatic and aromatic.

For now, let's focus on alifhatic

hydrocarbons and we'll cover aromatic

hydrocarbons later. Aliphatic

hydrocarbons are further divided into

three types alkanes, alkenes, and

alkyes. The simplest group of

hydrocarbons is called alkanes and the

smallest one is methane which has one

carbon atom connected to four hydrogen

atoms because carbon always forms four

bonds. Next is ethane and propane. If

you look at these compounds, you will

notice they increase by one carbon and

two hydrogens each time, but they are

otherwise quite similar. We call groups

of compounds like this a homologous

series, which means they have similar

properties and react in similar ways.

For alkanes, the general formula is CNH

2 N +2. This might look tricky, but it

just means that if a compound has n

carbon atoms, it will have 2 * N + 2

hydrogen atoms. For example, if we have

propane, which has three carbon atoms,

we can calculate its hydrogen count as 2

* 3 + 2, giving it 8 hydrogens. This

formula helps us to figure out the

molecular formula of larger alkanes too.

Take octane for instance, which has

eight carbon atoms. Using the formula we

calculate it will have 18 hydrogens. One

important thing to note is that alkanes

are saturated compounds meaning every

carbon atom forms four single bonds.

There are no double bonds. If we change

one of the single bonds in propane to a

double bond the carbons involved would

lose a hydrogen and the compound would

no longer be an alkan and will be

changed to alken. So I think it's a good

time to explain alkenes. Now alkenes are

another important group of hydrocarbons

but they differ from alkanes in a

significant way. They contain at least

one carbon-to-arbon double bond. The

presence of double bond is responsible

for making them unsaturated

hydrocarbons. The simplest alken is

ethine which has two carbon atoms

connected by a double bond and each

carbon is also bonded to two hydrogen

atoms. Moving up the series, we have

propene. It consists of three carbon

atoms but only two of them are connected

by a double bond while the third carbon

forms single bonds. If you look at the

number of hydrogens's in each molecule,

you will notice that alkenes have fewer

hydrogens than alkanes with the same

number of carbons. This is because the

double bond replaces two single bonds.

Like alkanes, alkenes also form a

homologous series, meaning they share

similar chemical properties and can be

described by a general formula. For

alkenes, the formula is

CNH2N. This is simpler than the formula

for alkanes because the presence of the

double bond reduces the hydrogen count.

Let's use propene as an example. with

three carbon atoms. The formula tells us

it should have 2 * 3 hydrogens, giving

us six hydrogens. This pattern holds

true as you go up the series. It's also

crucial to note that because of the

double bond, alkenes are much more

reactive than alkanes. This reactivity

allows them to undergo a wide range of

chemical reactions that are not possible

for alkanes, such as addition reactions,

where atoms or groups of atoms can add

across the double bond. This property of

alkenes plays a major role in industrial

processes such as the production of

plastics like polyethylene. Now we can

go to alkynes portion. Alkyes are

another key class of hydrocarbons but

they are even more reactive than

alkenes. The main feature that

distinguishes alkyes is the presence of

a carbontocarbon triple bond which makes

them unsaturated hydrocarbons like

alkenes but with an even higher level of

unsaturation. The simplest alkine is

ethine commonly known as acetylene with

the molecular formula C2H2. In ethine,

two carbon atoms are joined by a triple

bond and each carbon is connected to a

single hydrogen atom. As we move to the

next alkine, we get propine C3H4 which

has three carbon atoms. Similar to

alkenes, alkyes also form a homologous

series and their chemical behavior can

be predicted using a general formula.

For alkynes, the formula is CNH 2 N

minus2. This means that alkyes have even

fewer hydrogen atoms compared to alkanes

and alkenes due to the presence of the

triple bond. For instance, with propine,

if we apply the formula, we can

calculate that it should have 2 * 3

minus 2 hydrogens, giving us four

hydrogens, C3H4. The next member of the

alkine series, butine, follows the same

rule, resulting in C4H6. The triple bond

in alkynes is the key reason for their

high reactivity. It makes them much more

chemically versatile compared to alkanes

and alkenes. Alkyes can participate in a

variety of reactions including addition

reactions much like alkenes. But because

of the triple bond, these reactions

often occur in two steps. First breaking

the triple bond down to a double bond

and then further to a single bond. One

of the most important alkyes, ethan is

widely used in industrial applications

particularly in welding. Now let's move

towards aromatic hydrocarbons. They are

quite different from aliphatic

hydrocarbons. Actually those cyclic

compounds that contain at least one

benzene ring in their structure are

called aromatic hydrocarbons. Benzene is

a compound made up of six carbon and

hydrogen having cyclic hexagonal

structure with three alternate single

and double bonds. There are two main

types of aromatic hydrocarbons.

Monocyclic and polyyclic aromatic

hydrocarbons. Monocyclic aromatic

hydrocarbons are those aromatic

compounds that contain only one benzene

ring in their structure. The most common

example is benzene, a sixcarbon ring

with alternating single and double

bonds. In monocyclic compounds like

benzene, the ring structure is highly

stable due to the resonance where

electrons are deoized across the ring.

Their unique electron arrangement gives

them chemical stability and specific

reactivity patterns. These compounds

tend to undergo substitution reactions

where an atom or group is replaced but

the aromatic ring remains intact. Some

other examples are phenol, tluene and

analene. But polycyclic aromatic

hydrocarbons are those compounds

consisting of two or more interconnected

aromatic rings. For example, napylene

and anthraine. In this case, the rings

share carbon atoms and the resonance

extends over multiple rings making these

compounds even more stable. Polycyclic

aromatics hydrocarbons are more complex

and have multiple rings fused together.

They are commonly found in substances

like colar and are byproducts of

incomplete combustion due to their

larger structure. They have more varied

chemical behavior and are used in

industries for producing dyes, plastics

and other materials. The reactivity of

hydrocarbons depends on the type of

bonds between the carbon atoms. It means

that alkanes, alkenes and alkynes each

type shows different reactivity due to

the nature of their bonds. Alkanes

mostly undergo combustion reactions

which means burning an oxygen to produce

carbon dioxide and water and also

substitution reactions where one

hydrogen atom is replaced by another

atom like in halogenation where a

halogen like chlorine or bromine takes

the place of a hydrogen atom. However,

alkanes don't easily participate in

other reactions because their single

bonds are not very reactive. In some

cases, we also say that the sigma bond

in alkanes is inert which means it is

non-reactive. Alkenes on the other hand

contain at least one double bond and the

main reactions that alkenes undergo are

addition reactions where the double bond

is broken and atoms like hydrogen,

halogens or other groups are added to

the carbon atoms. For example, in

hydrogenation, hydrogen atoms are added

turning the alken into an alkan. Alkenes

can also react with halogens in

halogenation reactions and with water in

hydration reactions to form alcohols.

Alkyes are even more reactive than

alkenes. The triple bond in alkynes is

very reactive because it can be broken

in reactions that are similar to those

seen in alkenes. Alkyes also undergo

addition reactions where the triple bond

is broken and atoms are added to the

carbons. Since alkynes have more bonds

that can be broken, they can react in

two steps. First breaking one bond to

form a double bond and then breaking the

second bond to form a single bond. This

makes alkyes even more reactive than

alkenes. To sum up, the reactivity of

hydrocarbons alkanes are the least

reactive, showing mainly substitution

and combustion reactions. Alkenes are

more reactive, showing addition

reactions due to their double bonds.

Alkyes are the most reactive with their

triple bonds, making them capable of

multiple addition reactions. The overall

order of reactivity is alkyes greater

than alkenes greater than alkanes.