Functional Groups - Definition, Organic Compounds, Classes, FAQs

Edited By Team Careers360 | Updated on Jul 02, 2025 04:54 PM IST

The property of an organic compound will depend on the substituent or moiety present in it. Functional groups are a group of an atom that is even attached to an organic or bond that changes the chemical and physical property of an entire molecule. The different functional groups in an organic molecule the change in chemical properties drastic and also by different the molecule to which the functional group is attached the property will also change.

This Story also Contains

Functional Groups List
Functional Group Class 10
Functional Groups Table
Some Solved Examples
Conclusion

Functional Groups List

Functional groups can be charged for uncharged. Functional groups that contain any of the charges that are positive or negative are common one such example is COO^- that is carboxylate. And uncharged molecules do not contain a charge on them example OH functional group. Functional groups are ligands when it gets bonded to a coordination complex that is forming a coordination bond with metal atoms.

The presence of certain functional groups on a molecule also affects its solubility for example sugar is a molecule that contains OH group attached to it and is easily dissolvable in water which means that when a highly electronegative group here oxygen is get attached to a less electronegative atom or molecule hair hydrogen the polarity increases and thereby the solubility in water increases. Some of the functional groups are described below.

Hydrocarbons

NEET Highest Scoring Chapters & Topics

This ebook serves as a valuable study guide for NEET exams, specifically designed to assist students in light of recent changes and the removal of certain topics from the NEET exam.

Download EBook

Those functional groups that are hydrocarbons when they contain hydrogen and carbon atom. Alkanes, alkenes, alkynes, and benzene are some of the functional groups in hydrocarbons these are generally represented by the simple R. It also has the name hydrocarbyl group. The reactivity of these types of compounds is a dependent bond present in between the carbon atom that is a double or triple bond. And also reactivity depends on whether it is cyclic or acyclic. It is also present in the charged ions and uncharged form charged hydrocarbons are called carbocations with a positive charge and carbanions with a negative charge.

Alkyl Halides

Alkyl halides are functional groups that contain carbon and halogen bond. For the notation of this species, the name ‘halo’ is used. An example of this is CH₃Cl with the name methyl chloride. Depending on the type of halogen present on them the stability and the strength of these bonds change. For example, the carbon-fluorine bond is highly strong and highly stable compared to the carbon-iodine bond. Except for alkyl fluorides, all other haloalkanes undergo elimination and nucleophilic substitution reactions.

Oxygen-Containing Functional Groups

The functional group which contains an oxygen atom is the oxygen-containing functional group. It contains a carbon-oxygen bond. The bond present on them may be a double bond that is SP² hybridization and a single bond SP³ hybridized. The reactivity is also very is with the presence of a bond between them. There are various types of functional groups containing carbon-oxygen bonds so the naming also varies with the type of atom to which it is attached. Amide is an example where it contains nitrogen also.

Nitrogen-Containing Functional Group

The functional groups that contain nitrogen atoms are nitrogen-containing functional groups. These compounds are given the common name amine represented by NH₂. These are means may be primary, secondary, and tertiary as well. Depending on the number of carbon atoms present the naming also varies. If it contains only a single carbon atom can be named methylamine and if it contains two carbon atoms it is named dimethylamine and if it is 3 it is trimethylamine.

Related topics,

Functional Group Class 10

The groups of atoms or substituent or moiety get attached to an organic compound and thereby changing the whole molecule’s chemical and physical properties. And the new compound formed has property entirely different from the parent molecule. For example, benzene and phenol where an OH group is attached to the molecule. Properties of phenol and benzenes are extremely different.

Figure showing the structure of benzene

Figure showing the structure of phenol

Also read -

Priority Order of Functional Groups in IUPAC

For representing the position where the functional group is attached a priority order is necessary when a compound contains more than one functional group. From the IUPAC convention, the one with greater priority is carboxylic acid derivatives which include amides also. Of which amides have the highest priority then only carbonyls later alcohols then amines, alkenes, alkynes, and at last alkanes. If the compound contains a branch the longest carbon chain that is the one with higher carbon atoms is selected and is the parent compound. Anhydrides, esters, acid halides, acid halides have more priority than amides as well. The suffix for functional groups is shown in the functional group table.

The priority order for the functional group can be represented as;

Anhydrides>Esters>Acid halides>Amides>Nitriles>Alcohol>Amines>Alkenes>Alkynes>Alkanes

Also Read:

Functional Groups Table

The following figure will show the names and structure of some of the commonly used functional groups.

Functional group, structure, priorities

Some Solved Examples

Q 1. Compounds consist of particular atoms or groups of atoms on which all chemical properties depend known as -

(1) Prominent group

(2) Atom Group

(3) function group

(4) functional group

Solution:

As we learned

Functional group -

An atom, or group of atoms on which almost all chemical properties depend, is called a functional group.

$-\mathrm{COOH},-\mathrm{SO}_3 \mathrm{H},-\mathrm{COOR},-\mathrm{R}-\mathrm{COX}$

Hence, the answer is the option (4).

Q.2 Which of the following is not correctly matched to the name of the functional group?

1)ROH: Alcohol

2)RCOOH: Carboxylic Acid

3)$\mathrm{RCONH}_2$ : Amide

4) (correct)RCHO: Ketone

Solution

RCHO represents an Aldehyde and not a Ketone.

Hence, the answer is the option(4).

Conclusion

In organic chemistry, a functional group is a specific group of atoms or bonds within a compound that is responsible for the characteristic chemical reaction of that compound. The same function group will behave similarly, by undergoing similar reactions, regardless of the compound of which it is a part. The atoms or the group of atoms by which the characteristics reactions of organic compounds are determined, that atom or group of atoms is called a functional group.

Also check-

Frequently Asked Questions (FAQs)

1. Define functional?

Functional are those having special activities or tasks. In chemistry, it is the functional group which when attached to a particular molecule will change its physical and chemical properties.

2. What is r in organic chemistry?

R is an abbreviation used to represent hydrocarbon that is compounds containing carbon and hydrogen. R₁, R₂, R₃, etc. is also used to represent different hydrocarbon groups.

3. What is a functional group?

A particular group of atoms or substituent which when attached to a molecule will be responsible for the characteristic properties of that molecule. Amines, alcohols, anhydrides, acid chlorides, haloalkanes are some of the common examples.

4. Mention the functional group of amides.

Carbonyl is the functional group present in amides.

5. Define homologous series.

A series of compounds having similar chemical properties and same functional group are called homologous series.

6. What is the functional group of alcohol?

Hydroxyl group.

7. How do functional groups influence the naming of organic compounds?

Functional groups play a crucial role in naming organic compounds. They often determine the suffix or prefix used in the IUPAC name. For example, compounds with -OH groups are named as alcohols, while those with -COOH are named as carboxylic acids.

8. What is the importance of identifying functional groups in organic synthesis?

Identifying functional groups is crucial in organic synthesis because it helps chemists predict reactivity, plan synthetic routes, and understand potential side reactions. It allows for the strategic manipulation of molecules to create desired products.

9. What is meant by the term "isomeric functional groups"?

Isomeric functional groups are different arrangements of atoms that have the same molecular formula but different structures and properties. For example, aldehydes (R-CHO) and ketones (R-CO-R) are isomeric functional groups with the same carbonyl (C=O) group but different positions.

10. How do functional groups influence intermolecular forces?

Functional groups greatly affect intermolecular forces. Polar groups like -OH can form hydrogen bonds, increasing boiling points and solubility in polar solvents. Nonpolar groups like alkyl chains (-CH2-CH3) contribute to van der Waals forces, affecting properties like melting point and solubility in nonpolar solvents.

11. How do functional groups affect the reactivity of adjacent carbon atoms?

Functional groups can influence the reactivity of adjacent carbon atoms through electronic effects (inductive and resonance) and steric effects. For example, electron-withdrawing groups can make nearby carbons more electrophilic, while bulky groups can hinder reactions due to steric hindrance.

12. How do functional groups affect the acidity or basicity of a compound?

Functional groups can make a compound more acidic or basic by influencing the stability of the conjugate base or acid. For example, carboxylic acid groups (-COOH) increase acidity, while amine groups (-NH2) increase basicity.

13. How do functional groups affect the spectroscopic properties of organic compounds?

Functional groups have distinct effects on spectroscopic properties. In IR spectroscopy, they produce characteristic absorption bands. In NMR spectroscopy, they influence chemical shifts and coupling patterns. In mass spectrometry, they affect fragmentation patterns and molecular ion peaks.

14. What is the concept of functional group priority in organic nomenclature?

Functional group priority in nomenclature refers to the hierarchical system used to determine which functional group takes precedence when naming compounds with multiple functional groups. This system ensures consistent and unambiguous naming of complex organic molecules.

15. How do functional groups influence the color of organic compounds?

Certain functional groups, particularly those with conjugated systems like C=C, C=O, or aromatic rings, can affect a compound's ability to absorb visible light, thus influencing its color. These groups are called chromophores and are responsible for the colors we observe in many organic compounds.

16. What is the relationship between functional groups and organic reaction mechanisms?

Functional groups play a central role in organic reaction mechanisms. They determine the type of reactions a molecule can undergo, the reactive sites within the molecule, and the intermediates formed during the reaction. Understanding functional group behavior is key to predicting and explaining reaction mechanisms.

17. How do functional groups affect the physical properties of organic compounds?

Functional groups significantly influence physical properties such as boiling point, melting point, and solubility. For example, polar functional groups like -OH (hydroxyl) increase water solubility, while nonpolar groups like -CH3 (methyl) decrease it.

18. What are functional groups in organic chemistry?

Functional groups are specific arrangements of atoms within organic molecules that give the compound characteristic chemical properties. They are the reactive parts of molecules that determine how the compound will behave in chemical reactions.

19. Why are functional groups important in organic chemistry?

Functional groups are crucial because they determine the chemical behavior and reactivity of organic compounds. They allow chemists to predict and understand how molecules will interact, react, and behave in various chemical environments.

20. What is the difference between a functional group and a substituent?

A functional group is a specific arrangement of atoms that gives a compound its characteristic properties, while a substituent is any atom or group of atoms that replaces a hydrogen atom on the parent chain of a hydrocarbon. All functional groups can be substituents, but not all substituents are functional groups.

21. Can a molecule have multiple functional groups?

Yes, a molecule can have multiple functional groups. These compounds are called polyfunctional compounds. For example, amino acids have both an amine (-NH2) and a carboxylic acid (-COOH) group.

22. What is the concept of functional group interconversion?

Functional group interconversion refers to the process of changing one functional group into another through chemical reactions. This is a fundamental concept in organic synthesis, allowing chemists to modify molecules and create new compounds with different properties.

23. What is the significance of protecting groups in organic synthesis?

Protecting groups are temporary functional groups used to block the reactivity of certain parts of a molecule during a multi-step synthesis. They prevent unwanted side reactions and allow for selective transformations, playing a crucial role in complex organic syntheses.

24. What is the concept of bioisosterism in relation to functional groups?

Bioisosterism is the concept where functional groups with similar physical or chemical properties can be exchanged to create compounds with similar biological effects. This is widely used in medicinal chemistry to develop new drugs with improved properties or to circumvent patent restrictions.

25. What is the concept of functional group tolerance in organic reactions?

Functional group tolerance refers to the ability of a reaction to proceed without affecting other functional groups present in the molecule. It's an important consideration in complex syntheses, where selective reactivity is often required to avoid unwanted side reactions.

26. How do functional groups influence the optical properties of organic compounds?

Functional groups can affect optical properties such as refractive index, optical rotation, and circular dichroism. Chiral functional groups, for instance, can cause the rotation of plane-polarized light, a property important in stereochemistry and the pharmaceutical industry.

27. What is the concept of functional group masking in organic synthesis?

Functional group masking involves temporarily modifying a functional group to alter its reactivity during a synthesis. This technique allows chemists to carry out reactions on one part of a molecule without affecting sensitive functional groups elsewhere, enhancing synthetic flexibility.

28. How do functional groups affect the thermal stability of organic compounds?

Functional groups influence thermal stability by affecting bond strengths and potential decomposition pathways. Some groups can enhance stability through resonance or electronic effects, while others may introduce weak points or facilitate specific decomposition reactions under heat.

29. What is the concept of functional group orthogonality in organic synthesis?

Functional group orthogonality refers to the ability to selectively react with one functional group in the presence of others. This concept is crucial in complex syntheses, allowing chemists to manipulate specific parts of a molecule without affecting others, thus enabling more efficient and selective synthetic routes.

30. How do functional groups influence the stereochemistry of organic reactions?

Functional groups can affect stereochemistry by influencing the approach of reagents to reactive sites. They can create steric hindrance or electronic effects that favor certain stereochemical outcomes, playing a crucial role in determining the stereoselectivity of reactions.

31. How do functional groups affect the biological activity of organic compounds?

Functional groups greatly influence the biological activity of organic compounds by determining how they interact with biological targets like enzymes or receptors. They affect properties such as solubility, ability to form hydrogen bonds, and reactivity, all of which are crucial for drug-target interactions and metabolic processes.

32. How do functional groups influence the polarity of organic molecules?

Functional groups can significantly affect molecular polarity by introducing charge separation within the molecule. Polar functional groups like -OH or -NH2 create local dipoles, while the overall molecular polarity depends on the arrangement of these groups and the molecule's structure.

33. What is the importance of functional groups in polymer chemistry?

In polymer chemistry, functional groups are crucial for determining the properties and reactivity of monomers and polymers. They influence polymerization reactions, cross-linking, and the final properties of the polymer, such as strength, flexibility, and chemical resistance.

34. How do functional groups affect the oxidation state of carbon atoms?

Functional groups can change the oxidation state of carbon atoms. For example, replacing a C-H bond with a C-O bond (as in alcohols) increases the oxidation state of carbon. This concept is important in understanding oxidation and reduction reactions in organic chemistry.

35. What is the role of functional groups in determining a compound's odor?

Functional groups play a significant role in determining a compound's odor. Certain functional groups are associated with specific scents. For instance, esters often have fruity odors, while thiols (containing -SH) are known for their strong, unpleasant smells.

36. How do functional groups affect the melting and boiling points of organic compounds?

Functional groups influence melting and boiling points by affecting intermolecular forces. Groups that can form hydrogen bonds (like -OH) generally increase melting and boiling points, while nonpolar groups tend to lower them. The size and polarity of the functional group are key factors.

37. How do functional groups influence the aromaticity of organic compounds?

Functional groups can affect aromaticity by donating or withdrawing electrons from aromatic systems. Electron-donating groups (like -OH) increase electron density in the ring, while electron-withdrawing groups (like -NO2) decrease it, influencing the compound's aromatic character and reactivity.

38. What is the significance of functional groups in retrosynthetic analysis?

In retrosynthetic analysis, functional groups are key to planning synthetic routes. They serve as strategic disconnection points and guide the selection of appropriate reactions to transform complex target molecules into simpler precursors.

39. How do functional groups affect the solubility of organic compounds in different solvents?

Functional groups determine solubility by influencing a compound's ability to interact with solvent molecules. Polar groups enhance solubility in polar solvents like water, while nonpolar groups increase solubility in nonpolar solvents like hexane, following the "like dissolves like" principle.

40. What is the role of functional groups in determining a compound's toxicity?

Functional groups can significantly influence a compound's toxicity by affecting its reactivity, metabolism, and ability to interact with biological targets. Some functional groups are associated with specific toxic effects, which is crucial information in toxicology and drug development.

41. How do functional groups influence the stability of organic compounds?

Functional groups affect compound stability through electronic and steric effects. Some groups can stabilize molecules by distributing charge or providing resonance stabilization, while others may introduce strain or reactivity that decreases stability.

42. What is the importance of functional groups in understanding organic reaction energetics?

Functional groups play a crucial role in reaction energetics by influencing bond strengths, activation energies, and the stability of intermediates and transition states. Understanding how functional groups affect these factors is key to predicting reaction feasibility and rates.

43. How do functional groups affect the crystalline structure of organic solids?

Functional groups influence crystal packing and intermolecular interactions in organic solids. They can form specific patterns of hydrogen bonding or other intermolecular forces, which determine crystal structure, polymorphism, and physical properties like solubility and melting point.

44. What is the concept of functional group interchangeability in drug design?

Functional group interchangeability in drug design refers to the strategic replacement of one functional group with another to optimize drug properties. This approach is used to improve factors like potency, selectivity, bioavailability, or metabolic stability while maintaining the drug's core activity.

45. How do functional groups influence the photochemical properties of organic compounds?

Functional groups can significantly affect a compound's interaction with light. Certain groups, especially those with conjugated systems, can absorb specific wavelengths of light, leading to photochemical reactions. This is important in fields like photochemistry and the design of photosensitive materials.

46. What is the role of functional groups in determining a compound's lipophilicity?

Functional groups greatly influence lipophilicity, which is a measure of a compound's ability to dissolve in fats, oils, and non-polar solvents. Nonpolar groups increase lipophilicity, while polar groups decrease it. This property is crucial in drug design and understanding how compounds interact with biological membranes.

47. How do functional groups affect the rate of organic reactions?

Functional groups can accelerate or decelerate reaction rates by influencing factors such as electron density, steric hindrance, and the stability of transition states or intermediates. Understanding these effects is crucial for predicting and controlling reaction kinetics.

48. What is the importance of functional groups in supramolecular chemistry?

In supramolecular chemistry, functional groups are essential for creating non-covalent interactions between molecules. They determine how molecules recognize and bind to each other, forming complex supramolecular structures like molecular machines, sensors, and self-assembling systems.

49. How do functional groups affect the electron density distribution in organic molecules?

Functional groups influence electron density distribution through inductive and resonance effects. Electron-withdrawing groups decrease electron density in nearby atoms, while electron-donating groups increase it. This distribution affects the molecule's reactivity and properties.

50. What is the role of functional groups in determining a compound's partition coefficient?

Functional groups significantly influence a compound's partition coefficient, which measures its distribution between two immiscible phases (often water and octanol). Polar groups tend to decrease the partition coefficient, favoring the aqueous phase, while nonpolar groups increase it, favoring the organic phase.

51. What is the importance of functional groups in green chemistry?

In green chemistry, understanding functional groups is crucial for designing environmentally friendly reactions and products. Certain functional groups can make compounds more biodegradable, less toxic, or more easily recycled, aligning with the principles of sustainable chemistry.

52. How do functional groups influence the conductivity of organic compounds?

Functional groups can affect a compound's electrical conductivity by influencing its electronic structure. Conjugated systems with certain functional groups can facilitate electron movement, leading to conductive properties important in organic electronics and conductive polymers.

53. How do functional groups affect the surface tension of organic liquids?

Functional groups influence surface tension by affecting intermolecular forces at the liquid-air interface. Polar groups generally increase surface tension due to stronger intermolecular attractions, while nonpolar groups tend to decrease it. This property is important in applications like detergents and coatings.

54. What is the role of functional groups in determining a compound's vapor pressure?

Functional groups affect vapor pressure by influencing intermolecular forces. Groups that increase intermolecular attractions (like hydrogen bonding groups) generally decrease vapor pressure, while those that reduce these attractions increase it. This impacts properties like volatility and boiling point.

55. What is the importance of functional groups in understanding metabolic pathways?

Functional groups are key to understanding metabolic pathways as they determine how organic molecules are processed in biological systems. They influence enzyme recognition, reactivity in biochemical reactions, and the transformations that occur during metabolism.

56. How do functional groups affect the fluorescence properties of organic compounds?

Functional groups can significantly influence a compound's fluorescence by affecting its electronic structure. Certain groups, especially those with conjugated systems, can enhance or quench fluorescence, which is important in applications like fluorescent labeling and sensor development.