Why is C2H4 not an alkane?
The formula for an alkane is CnH(2n+2). Since n is 2, H must be 2*2+2 = 6 to be an alkane and it isn't that.
To understand why C2H4 (ethylene) is not considered an alkane, we need to review the definition of an alkane.
Alkanes are hydrocarbons that consist solely of carbon (C) and hydrogen (H) atoms, bonded together by single covalent bonds. The general formula for alkanes is CnH2n+2, where "n" represents the number of carbon atoms.
The molecular formula of ethylene or C2H4 suggests that it contains two carbon atoms and four hydrogen atoms. However, ethylene is not an alkane because it does not contain only single covalent bonds between carbon atoms.
In the case of ethylene, the two carbon atoms are bonded by a double bond. This double bond consists of one sigma (σ) bond and one pi (π) bond. The presence of a double bond makes ethylene an unsaturated hydrocarbon and places it in a different category of organic compounds called alkenes.
The general formula for alkenes is CnH2n. Unlike alkanes, alkenes have at least one double bond between carbon atoms.
In summary, C2H4 (ethylene) is not considered an alkane because it contains a double bond between the two carbon atoms, which categorizes it as an alkene.