Naming an organic compound is an integral part of the chemistry syllabus of any school going, student. Hence, it is important to know all the rules used in naming an organic compound. In this guide, we’ll help you get a brief knowledge of the main functional groups based on the IUPAC nomenclature, the order of precedence of the groups, and other essential rules. The blog will also help you answer the question, How to name organic compounds using the IUPAC rules? First, let’s understand what IUPAC stands for inorganic chemistry.
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What is IUPAC Nomenclature?
IUPAC stands for International Union of Pure and Applied Chemistry. It is a concept in the chemical nomenclature for naming organic chemical compounds. The publication of the terminology took place in the Nomenclature of Organic Chemistry, also called a blue book. According to the IUPAC Nomenclature concept, any known organic compound should have a name to derive a structural formula. The prime reason to bring up the IUPAC Nomenclature concept was to avoid long names of the organic compounds used in everyday communication. These names are easy to spell, understand, and use to study the chemistry of any compound.
Rules of IUPAC Nomenclature
IUPAC nomenclature for an organic compound represents some guidelines to be followed in their naming. As per the rules, there are six different points to remember.
The Longest Chain Rule
According to the first rule, the parent hydrocarbon has to be identified and named. To find the parent chain from the compound, consider looking for the longest one. Their shape can be either straight-chain or in any other shape.
The Lowest Set of Locants
As per the rule, the carbon atoms belonging to the parent hydrocarbon chain must be numbered using the natural numbers. Also remember, the naming must start from the end in which the carbon atom with the substituents gets the lowest number.
Multiple Instances of the Same Substituent
In the third rule, the compounds get the prefixes that indicate the total number of the same substituent in the give organic compounds, such as di, tri, etc.
The naming of Different Substituents
In the organic compounds with multiple substituents, the corresponding substituents arrange themselves in alphabetical order of names in the IUPAC nomenclature.
Naming Different Substituents Present at the Same Positions
As per this rule, when two different substituent groups are present at the same organic compound position, the substituents are named in the ascending alphabetical order.
Naming Complex Substituents
According to this rule, the complex substituents of the organic compounds with branched structure must be named substituted alkyl groups. The named branched and complex substituents must be written in brackets in the IUPAC nomenclature.
Format of IUPAC Nomenclature
Now that you know the different rules under the IUPAC nomenclature, here is the format that you must follow to write sound scientific names.
IUPAC nomenclature of organic compound follows the format of:-
Locant + Prefix + Root + Locant + Suffix
Root
The word root in the IUPAC Nomenclature signifies the total number of carbon atoms present in the longest carbon chain belonging to the compound.
E.g.:- Meth is the root name for one carbon atom, and Pent refers to the chain with five carbon atoms.
Suffix
The suffix in the IUPAC nomenclature refers to a functional group belonging to the molecule, which follows its root. The suffix further divides up into five types namely:-
Primary suffix
It is written just after the word root in alkanes, where the suffix is ane.
Secondary suffix
It is generally written after the primary suffix.
E.g.:- For compounds with an alkane or alcohol group attached to it, it will be named an alkanol, will of being the secondary suffix of the alcohol group.
Prefix
Another part of the name of an organic compound is the prefix. It is added before the root of the compounds named as per IUPAC nomenclature. There are two types of prefixes.
Primary Prefixes
It indicates the cyclic or acyclic nature of the given compound.
E.g.:- cyclo is used as a prefix for cyclic compounds.
Secondary Prefixes
This prefix type indicates the presence of side chains or subsequent groups.
E.g.:- ‘CH3’ group also called a methyl group.
IUPAC Nomenclature of Aliphatic Compounds
The IUPAC nomenclature of alkanes, alkenes, and alkynes are some important Aliphatic compound, whose name you must know.
Alkanes
The general formula of alkanes corresponds to CnH2n+2.
The suffix ‘ane’ is used to describe alkanes.
Eg:-Methane for the compound CH4 and Butane for the compound C4H10.
Alkenes
The general formula of alkenes corresponds to CnH2n.
The suffix ‘ene’ is used to describe alkenes via IUPAC norms.
E.g.:- ethene describes the compound given by C2H4 and propane used to the compound given by C3H6.
Alkynes
The general formula of alkynes is CnH2n-2
The suffix ‘yne’ is used to describe alkynes. E.g.:- ethyne is used to describe the compound by C2H2.
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