Its an alkyl derivative of ethane.

Alkanes have the formula ##C_n H_(2n+2)## where in n is the number of carbon atoms.

Alkanes have their carbons saturated with hydrogens and have no double bonds. An example is ethane.

##CH_3CH_3## or simply ##C_2H_5##

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Now let us have a look in alkyl groups.

Alkyl groups are organic groups(they usually act as substituents) that are alkanes lacking one carbon and hence, ##C_2H_(2n+1)## . Because they are derived from alkanes, we call them alkane derivatives.

Take a look at the structure given above. Remove 1 hydrogen from ##C_2H_6## (which is an alkane, ##C_((2))H_(2(2)+2) = C_2H_6##, proving it is an alkane), the resulting structure is ##C_2H_5##, an alkyl group.

Remember that carbons have to be tetravalent. That is, its valence electrons need 4 electrons to bond covalently (see Octet rule). However, because we removed 1 Hydrogen atom, there is one valence electron that has no partner.

So some atoms or groups may bind to that missing valence electron. For example, i chose to put a hydroxyl group (OH-) to satisfy the missing valence electron. The resultant compound is now ##C_2H_5OH##, ethyl alcohol.

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