Functional groups: Definition, Roles, Nomenclature and Examples

Functional groups are the substituent or moiety in a molecule that generates the molecule's unique chemical reactions. Regardless of the makeup of the remaining parts of the molecule, the same functional group will experience the same or a similar set of chemical reactions. 

• This makes it possible to plan chemical synthesis and to predict chemical reactions and compound behaviour in a systematic way. 
• The reason the functional group strategy "works" is that certain functional groups' characteristics and reaction chemistry can be surprisingly independent of the environment. 
• Because of this, it is possible to anticipate the chemical behaviour of thousands of actual organic molecules by simply understanding the chemistry of a few general functions.

Key Terms: Functional Groups, Hydrocarbons, Alkenes, Haloalkanes, Ketones, Covalent bond, Ether, Ester, Carbon. 

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What are Functional Groups?

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A functional group is an atom or group of atoms inside a molecule that share chemical properties when they appear in other compounds. Covalent bonds bind the atoms in a functional group to one another and to the other molecules in the molecule. Functional groups connect to the nonpolar carbon atom core of repeating polymer units, giving carbon chains a chemically distinct appearance. 

• Furthermore, functional groups may be charged. 
• It is possible for two molecules of similar or identical size but with the same functional groups to engage in chemical reactions. 
• A molecule's behaviour and chemical reactions can be anticipated with high accuracy if it has a functional group. 
• Functional groups can be found in lipids, proteins, and carbohydrates.

Read More: Carbon and Its Compound

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Role of Functional Groups

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Other functional groups can be used to further modify the way that the functional groups participate in a chemical reaction, and these groups can also be transformed into one another. There are a few carbon-based functional groupings. Thus, it is clear that functional groups are moieties that display their own unique characteristics and properties apart from the molecules to which they are linked.

• When it comes to polymers, the functional groups are often attached to the nonpolar centres of the carbon atoms in each repeating unit of the corresponding polymer, giving the carbon chain specific chemical characteristics.
• It has been noted that some functional groups have an ionic charge associated with them, such as in carboxylate salts that include the -COO- ionic group.
• Depending on their makeup, these groups when joined to molecules change the molecule into either polyatomic ions or complexions.
• In a coordination complex, the functional group that is bonded to the main atom is referred to as the ligand.
• These groups' atoms and the group as a whole are joined to the molecule through covalent bonds.

Read More: Aldehyde and Ketone general formula

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Nomenclature of Common Functional Groups

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This subsection contains a list of the most frequent functional groups as well as the prefix and suffixes that must be used when naming them.

1. Hydrocarbons – Hydrogen and carbon are the only components of this kind of functional group. 'R' is a frequent way to represent them. Additionally known as hydrocarbyl groups. Single, double, or triple bonds can be created between carbon atoms. 

• The bonds between carbon and hydrogen are always solitary. 
• Because of how the carbon-carbon bond is structured, these groups' reactivity varies. 
• They might be ringed or branching. 
• These functional groups may include charges in some instances. 
• Carbocations are hydrocarbon groups that are positively charged, whereas carbanions are those that are negatively charged.

2. Haloalkanes – A class of chemical compounds called haloalkanes, commonly referred to as alkyl halides, is made up of an alkane with one or more hydrogen atoms from Group 17 substituted by a halogen atom. 

• The structural and physical characteristics of haloalkanes and those of alkanes can be distinguished from one another in a pretty significant way. 
• The length and number of branches of the carbon atoms as well as the kind and arrangement of the halogens in the molecule all affect how stable haloalkanes are. 
• As an illustration, the bond between carbon and fluorine is more powerful than the bond between carbon and chlorine.
• Haloalkanes are found in haloalcohol fire extinguishers, refrigerants, propellants, solvents, and medicines. 
• They are a substantial source of pollution as well, and certain products no longer use them entirely.

3. Functional Groups Containing Oxygen – The existence of a carbon-oxygen link in the arrangement is the primary characteristic of this classification of functional groups. 

• The degree of hybridization completely determines the type of connection. 
• The oxygen's role as an electron donor during the sp³ hybridization is used to explain it. 
• This effect can be seen with alcohol. 
• On the other hand, any carbon-oxygen double bond (C=O) exhibits the sp² hybridization and associated withdrawing action. 
• In other functional groups, atoms of different elements like nitrogen, sulfur, phosphorus, etc. are present.

Read More: Carbonyl functional groups

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Functional Groups with Examples

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Some of the functional groups are - 

• Alcohol (-OH)

Alcohol is the name of the chemical compound created by this functional group, which has the suffix -ol. Methanol or methyl alcohol are two examples.

• Aldehyde (-CHO)

A carbon atom and two hydrogen and oxygen atoms are joined in this functional group, leaving a free bond for another atom to join. 'al' is a suffix on the compounds. Ethanal or acetaldehyde (CH₃CHO) is an example.

• Ketone (=CO)

A double bond holds a carbon atom to an oxygen atom in this functional group. 'One' serves as the suffix. Acetone (CH₃COCH₃) is an example.

• Acyl Halide (-COX)

The carbon atom in this functional group is joined to a halogen atom. 'Oyl halide' is its suffix. Ethanoyl Chloride (CH₃COCl) is an example.

• Carboxyl (-COOH)

A carbon atom is joined to an oxygen atom in this functional group, and there is also a hydroxyl group present. Its suffix is either "oic" for the aid form or "oate" for the salt or ester form. Examples include sodium ethanoate (CH₃COONa) and ethanoic acid (CH₃COOH).

• Ether (-C-O-C-)

An oxygen atom forms this functional group when it is doubly linked to two carbon atoms. 'Alkyl ether' is its suffix. Diethyl ether is an example (CH₃CH₂OCH₂CH₃).

• Ester (-COO-)

Alcohol and organic acid react to form this functional group. It is essentially an organic acid-base reaction that results in the production of an ester, an organic salt. Ethyl ethanoate, for instance (CH₃COOC₂H₅).

Read More: Isomerism

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Things to Remember

• In organic chemistry, a functional group is a collection of atoms or bonds that is in charge of a substance's particular chemical processes.
• When a molecule has a functional group, it means that its behavior and chemical reactions may be predictably anticipated in a systematic way.
• These groups' atoms and the group as a whole are joined to the molecule through covalent bonds.
• Functional groups can have an impact on a molecule's solubility as well as its propensity to form complexes. If the functional groups of the solute and the solvent interact well, the solubility increases.
• Alkanes, alkenes, and alkynes (as well as benzene derivatives sometimes) are represented by the letter R. These groupings are also known as hydrocarbyl groups.
• Haloalkanes, also known as alkyl halides, are functional groups with a link between a carbon atom and a halogen.
• The first carbon atom is referred to as alpha carbon, the second carbon atom is referred to as beta carbon, and so on, in the case of carbon atoms coupled to functional groups.