Chemistry · General Principles Of Organic Chemistry · NEET
Not exactly. A functional group is the reactive part that decides the chemical behaviour of the whole molecule, like -OH, -CHO or -COOH. An alkyl group such as -CH3 is only a chain branch and is not counted as a reactive functional group. A halogen like -Cl is treated as a functional group (haloalkane) because it does control reactions such as substitution. For NEET, remember: -OH, -CHO, >C=O, -COOH, -NH2, -CN, -NO2, C=C, C tripple bond C and -X are functional groups.
A functional group is a single feature inside one molecule. A homologous series is a whole family of compounds that all share the same functional group and differ only by -CH2. So all alcohols (CH3OH, C2H5OH, C3H7OH) form one homologous series because they all carry the -OH functional group. The functional group is the reason the members behave alike.
Yes. A C=C double bond (alkene) and a C tripple bond C triple bond (alkyne) are functional groups, because they are the reactive centres that undergo addition reactions. A plain C-C single bond in an alkane is not a functional group, which is why alkanes are fairly unreactive.
Look past the plain -CH2- and -CH3 carbons and hunt for any atom that is not carbon or hydrogen, or any multiple bond. An O, N, halogen, or a double/triple bond is almost always part of the functional group. Then match the arrangement: C=O with H is -CHO (aldehyde), C=O between two carbons is a ketone, C=O with -OH is -COOH (acid).
The carbon chain (made of strong, non-polar C-C and C-H bonds) is stable and mostly unreactive. The functional group usually has polar bonds, lone pairs, or pi electrons, so it is where electrons can move and reactions can start. That is why methanol and octanol, though very different in chain length, both react like alcohols.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
It is the atom or small group of atoms in an organic molecule that controls how the molecule reacts, such as -OH in alcohols or -COOH in acids.
Hydroxyl -OH (alcohol), aldehyde -CHO, ketone >C=O, carboxylic acid -COOH, and amino -NH2 (amine). Also important: -CN, -NO2, -X (halide), C=C and C triple bond C.
Because compounds with the same functional group show similar chemical reactions, so learning one group lets you predict the behaviour of a whole family of compounds. This saves time in NEET reasoning questions.
Yes. Molecules like amino acids carry both -NH2 and -COOH. When naming them, the group with higher priority becomes the main suffix and the other becomes a prefix.
The benzene ring is usually treated as the parent (aryl) structure, not as a functional group. Groups attached to it, like -OH in phenol or -NO2 in nitrobenzene, are the functional groups.
