# Differentiate between alkane, alkyne, alkene and alkyl ? Give at least 3 major differences of them.

Jun 10, 2018

Below are the differences between the four stated as a list.

#### Explanation:

• Alkane:-
They are hydrocarbons which are joined by single bonds only. Thus called as saturated hydrocarbons They are less reactive in nature as the carbons bonds are stable.They are also called paraffins They are simplest of the hydrocarbons which have no functional groups attached to the carbon atoms. Some examples are Methane-$C {H}_{4}$ Ethane- ${C}_{2} {H}_{6}$ etc. The general formula is ${C}_{n} {H}_{2 n + 2}$.

• Alkene:-
They are joined by at least one double bond between them.They are reactive in nature and are called as unsaturated hydrocarbons. Without the presence of any functional group they are called as olefin. They have $\pi$ bond between the atoms which is generally the reason for their reactive nature. Some of the examples are Ethene- ${C}_{2} {H}_{2}$ , Propene-${C}_{3} {H}_{6}$ etc.Their general formula (not including cyclic compound) is ${C}_{n} {H}_{2 n}$.

• Alkyl:-
They are the hydrocarbons which are formed when one hydrogen molecule is removed from the alkane(it can be any alkane).They are normally reactive in nature. Their examples include - Methyl-$C {H}_{3}$, Ethyl-${C}_{2} {H}_{5}$ etc. Their general formula(not including cyclic compounds) is ${C}_{n} {H}_{2 n + 1}$. They tend to exist as a part of a bigger molecule i.e. derivatives of the alkane groups.

• Alkyne:-
They are unsaturated hydrocarbons which are having at least one triple bond between them.They are also called as acetylenes.They are also reactive in nature i.e. most reactive between the alkane, alkene and alkyl. Some of the examples are Ethyne-${C}_{2} {H}_{2}$ and Propyne-${C}_{3} {H}_{4}$ etc.Their general formula is ${C}_{n} {H}_{2 n - 2}$.

But the major difference between them is their structure and their way of reactivity. Their general formula is also a way of differentiating between them.

Jun 11, 2018

Well, clearly, these species have DIFFERENT $\text{degrees of unsaturation...}$

#### Explanation:

...............A very useful metric that is used to rationalize the formulae of organic compounds is their $\text{degree of unsaturation}$. An alkane is said to be fully $\text{saturated}$, and it contains the MAXIMUM ALLOWABLE number of $C - H$ bonds.

AND so $\text{FULLY saturated}$ alkanes have a general formula of ${C}_{n} {H}_{2 n + 2}$. Try this out for $\text{methane,}$ $\text{ethane,}$ .........$\text{pentane, etc.}$

Each double bond, each olefinic bond or carbonyl group, OR ring junction, corresponds to 1""^@ of unsaturation; i.e. 2 hydrogens LESS than the saturated formula. So according to the scheme, $\text{ethane}$ has the saturated formula of ${H}_{3} C - C {H}_{3}$, but $\text{ethylene}$, ${H}_{2} C = C {H}_{2}$, and $\text{acetaldehyde}$, ${H}_{3} C - C \left(= O\right) H$ has ${1}^{\circ}$ of unsaturation. Halogen atoms count for one hydrogen; for nitrogen atoms, substract $N H$ from the formula before assessing unsaturation; i.e. for $\text{ethylamine,}$ ${H}_{2} N C {H}_{2} C {H}_{3}$ $\rightarrow {C}_{2} {H}_{6}$, i.e. $\text{no degrees of unsaturation}$. Cyclohexane, ${C}_{6} {H}_{12}$ ALSO has one degree of unsaturation given the ring junction the which reduces the hydrogen by TWO...i.e. one degree...

On the other hand, an alkyl substituent has formula of ${C}_{n} {H}_{2 n + 1}$... Assessment of the degree of unsaturation is one of the first things you do with an organic formula.

And so what are the three differences? Alkanes (when substituted) typically undergo substitution or elimination reactions. Olefins and acetylenes can undergo addition reactions. And of course the degree of unsaturation....