Content Curator
Nomenclature is a method of the set of rules which are used for forming the terms or names of a distinct field in subjects such as science and arts. The organic compounds which include carbon and hydrogen single bonds are called Saturated hydrocarbons. There is a maximum number of hydrogen atoms present for every carbon atom in these saturated hydrocarbon compounds. Saturated hydrocarbons can be cyclic or acyclic. Alkanes are saturated acyclic hydrocarbons. Primary suffix for single bond is ane.
Read Also: Aliphatic Hydrocarbons
| Table of Content |
Key Terms: Alkane, hydrocarbon, alkyl groups, organic compounds, straight-chain, nomenclature, closed- chain, single bond
Saturated Hydrocarbons
[Click Here for Sample Questions]
In a saturated hydrocarbon, all the carbon atoms are connected by a single bond. Saturated hydrocarbons are also known as alkanes. An alkane is a type of hydrocarbon in which all the carbon atoms are connected together only by a single covalent bond. You cannot find double or triple bonds in an alkane. Therefore, the hydrocarbons methane, ethane, propane and butane form a series of compounds called alkanes. All the saturated hydrocarbons have the suffix ‘ane’ at the end of their names.
Check Important Notes on Properties of Carbon and its Types
Unsaturated Hydrocarbons
[Click Here for Sample Questions]
In an unsaturated hydrocarbon, the two carbon atoms are connected by a double bond or triple bond. Ethene and ethyne are two most important unsaturated hydrocarbons. The reason behind that is ethene contains a double bond and ethyne contains a triple bond between the two carbon atoms. Unsaturated hydrocarbons are mainly of two types:
- Carbon-carbon double bond known as alkenes
- Carbon-carbon triple bond known as alkynes
Read More: Difference Between Element and Compounds
IUPAC nomenclature rules for saturated hydrocarbons
[Click Here for Sample Questions]
By these following rules the saturated hydrocarbons are named:
Longest Chain Rule
The main or the parent chain of the compound is known as the longest chain of carbon atoms. This parent chain can be straight or any other shape. According to IUPAC nomenclature rules the straight chain alkanes have suffix ane to the root word. Straight chain alkanes including 1, 2 or 3 carbon atoms are methane, ethane and propane.
Lowest Locant Rule
The numbering has been done in such a way that the branched chain i.e., the alkyl group gets the lowest possible number. The numbering of carbon atoms starts from the end in these types of chains. It in turn gives the lowest number to the carbon atom which is carrying the substituent.
Read Further: Huckel Rule
Presence of Same Substitute More Than Once
In this condition, the number of occurrences of the same substituent is more than that of the parent chain at different positions, the number of each occurrence gets separated by commas. They are given the prefixes to the substituent which are present twice and thrice on the parent chain. The prefixes are di (substituents which are present twice) and tri (substituents which are present thrice).
Giving Names to Different Substituents
If two or more alkyl groups are present on the parent chain then their names are written in an alphabetical order. It is nearer to the alkyl group because numbering is done from the side.
Naming Complex Substituents
If the substituent on the parent chain has a branched structure, the naming of complex substituent is done. These are named as a substituted alkyl group. The carbon atom attached to the parent chain is numbered as 1. The names for these types of substituents are written in brackets.
Giving Names to Different Substituents at Equivalent Positions
When two different substituents are present on the same position on the parent chain from the two ends, they are named by whichever substituents come first in the alphabetical order gets the lowest number.
Also Check:
Things To Remember
[Click Here for Sample Questions]
- When all the carbon atoms are linked to one another by only a single bond in a hydrocarbon, then they are known as saturated hydrocarbons.
- Alkanes are the saturated acyclic hydrocarbons which have the primary suffix ane.
- Carbon chains which are attached to the parent chain are called an alkyl group.
- The names are written in an alphabetical order, when two or more alkyl groups are present on the main parent chain.
- The principal chain is the longest continuous chain present in an alkane.
Check Also: Unsaturated Hydrocarbons
Sample Questions
Ques. What are the saturated hydrocarbons commonly known as? (2 marks)
Ans. Saturated hydrocarbons are commonly known as alkanes. They contain a large number of hydrogen atoms within them and therefore they are known as alkanes. All the carbon bonds in alkane are linked to one another only by a single bond. They have the suffix ane. CnH2n+2 is the general formula that alkanes have, where n is the number of carbon atoms. Alkanes are subdivided into three groups which are chain alkanes, cycloalkanes and the branched alkanes.
Ques. Which is the smallest alkane which can form a ring structure? (2 marks)
Ans. Cyclopropane is the smallest alkane that can form a ring-like structure or cycloalkane. It has a C-C bond on removal of a hydrogen atom. In Cyclopropane, three carbon atoms form a ring structure. The formula for cyclopropane is C3H6. Cyclopropane is used as a general anaesthetic. It is a cycloalkane which has three methylene groups linked to each other.
Ques. Which are the substituent groups that are commonly associated with benzene rings? (2 marks)
Ans. Phenyl and benzyl are the substituent groups that are commonly associated with benzene rings. Their structure is closely associated with differences in hydrogen atoms. Benzene ring is an aromatic functional group which has a ring of six atoms. It is bounded by alternating single and double bonds. The structure of benzene ring is as shown below.:
Ques. What will be the group formed by the triple bond with two carbon atoms on either side? (2 marks)
Ans. Triple bonds with two carbon atoms on either side are known as ethynyl groups. Those bonds with one carbon on one side and two carbons on another side are known as propargyl groups. The ethynyl group has a suffix yne. It is also known as the acetylenic group or ethinyl group in compounds.
Ques. How does the C=C bond in the chain of the compound is shown? (3 marks)
Ans. According to the rules of IUPAC of nomenclature, the C=C bond in the chain of the compound considered is depicted by specifying the number of the carbon atoms at the beginning of the C=C bond. Carbon to carbon is the covalent bond between two atoms. There are single bonds, double bonds and triple bonds in the compounds. By the below table, we can understand that if the compound has a single carbon bond it is called Alkane. On the other hand, if they have a double or triple bond they are known as Alkene and Alkyne respectively.
Ques. By which suffix, the substituent in the chain is named after replacing the “ane” in the alkanes? (2 marks)
Ans. In alkenes, eneis used as the suffix. In the carboxylic acids and ketones, ic and one are used to represent them respectively. Therefore, yl is the term which is to be substituted in the place of ane in the alkanes. This suffix is used to form radicals in organic chemistry. yl means that one hydrogen is replaced, while ylidene means that two hydrogens are replaced in the compound.
Ques. Which compounds are given the name Dienes? (2 marks)
Ans. One double bond compound is given the name alkenes, while the dienes are the compounds which are with two double bonds. The dienes are also known as diolefin. Dienes has two alkene units and has a prefix di as per the systematic nomenclature.Dienes are of complex molecules. They are mostly synthetic chemicals and usually used in organic synthesis. Following is the example for dienes which is butadiene.
Ques. In which alkane, a carbon atom is displaced so as to form a compact structure which resembles the butterfly wing? (3 marks)
Ans. In cyclobutene, a carbon atom is displaced so as to form a compact structure which results in the resemblance of the butterfly wing. When one of the carbon atoms of the compound cyclobutene is not displaced, then it will lead to the C- C bond. This C-C bond will be exactly at right angles to each other and they will not form a cyclic structure. It is a cycloalkane and an organic compound. C4H6 is the formula for cyclobutene.
Ques. The compound CH3COCH2CH2CH2COOH is known by which IUPAC name? Explain why the prefix oxo is used? (2 marks)
Ans. The compound is known as oxoacid. The molecules of this compound include a minimum of one hydroxy group bonded to an atom. As a result of that, it becomes double bonded to at least one oxygen atom. An oxyacid dissociates in water which in turn forms the H+ cation as well as the anion of the acid. X-O-H is the general structure of an oxyacid. The IUPAC name of CH3COCH2CH2CH2COOH is 5-oxohexanoic acid.
Ques. Write down the features of the IUPAC naming system. (3 marks)
Ans:
- Only one name is assigned to a particular given compound.
- The IUPAC name of the compound clearly directs in writing of one and only molecular structure.
- The IUPAC system is very helpful in naming multifunctional organic compounds.
- The IUPAC system is useful in naming complex organic compounds. It makes the process easier.
- The IUPAC method is systematic, easy to understand and scientific method of nomenclature of organic compounds.
Also check:
Comments