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While studying organic chemistry, we usually come across the words Primary, Secondary, tertiary, and quaternary. Carbon atoms as well as functional groups in an organic molecule can be said to be primary, secondary, tertiary, and quaternary.

Identifying the functional groups in terms of primary secondary and tertiary is very important since the properties and reactivities vary depending on whether it is primary, secondary, or tertiary.

Whether the carbon is primary, secondary, tertiary, or quaternary depends upon the number of other carbons directly attached to it.

In the case of functional groups, we count the number of carbon atoms attached to the carbon atom bonded to the functional group. For example-

Since, in this structure,the number of carbon atoms attached to the carbon bonded to the –OH, is one, it’s a primary alcohol.

(b)A Tertiary Nitrile-

In this structure,the number of carbon atoms attached to the carbon bonded to the CN group is three, it’s a tertiary nitrile.

(c)A Secondary Thiol-

In this structure, the number of carbon atoms attached to the carbon bonded to the –SH, is two, it’s a secondary thiol.

(d) Both primary and secondary alcohol-

In this structure,the number of carbon atoms attached to the carbon bonded to the –OH, is two, it’s a secondary alcohol. There is also an –OH group that is bonded to primary carbon, so primary and secondary alcoholic groups are present.

(e) An isopropyl group-

An isopropyl group is the simplest structure that contains a tertiary carbon. So, the structure is-

(f) A quaternary Carbon-

Quaternary carbon is the one that is attached to four other carbon atoms.