Primary, Secondary, and Tertiary Carbons
A carbon which is attached directly to only one other carbon is called a primary (10) carbon. If it is attached directly to two other carbons, it is a secondary (20) carbon. A carbon is called a tertiary (30) carbon, if it is directly attached to three other carbons.
Though alkanes are not so reactive, they can undergo some reactions by forming intermediates. These intermediates can be alkyl radicals, carbocations, or carbanions. Alkyl radicals are intermediates of free radical reactions. Carbocations (carbonium ions) are species with a positive charge on one of the carbon atoms. A carbanion has a negative charge on one of its carbon atoms. Some major trends are given below: