Nomenclature is the system of names or rules which is needed to form the terms in a particular field of art or science. The nomenclature of the alkane, alkene, and alkyne groups ate done by counting the number of carbon atoms in a long continuous chain, which includes double or triple bonds, and appending an adding proper suffix to the stem name.
Why is the nomenclature of alkane, alkene and alkyne important?
The nomenclature of alkane, alkene, and alkyne helps us to identify the compounds by just looking at the name without the need to look into the chemical structure. This helps us to better assess the property of the compound and group them accordingly. Alkane, alkene, and alkyne have specific properties due to their chemical structures. And naming will ensure the property associated with the group is reflected by directly looking up the name.
Alkane nomenclature
The hydrocarbons which have no double or triple bond functional groups are referred to as the alkenes or cycloalkanes. It depends on the carbon atoms of the molecules when they are arranged only in a chain or ring. These alkanes are members of a large class of compounds, which is referred to as aliphatic.
Steps for IUPAC nomenclature of alkanes:
1. First find the longest chain of carbon which is called as parent/backbone chain.
2. The number of chains at the end, which is closest to any substituent ensures the lowest possible number for positions of substituents.
3. This number is used to designate the location of the substituent groups, where the names are obtained by changing the -ane suffix to -yl.
•The substituents groups are listed alphabetically.
Examples of alkane nomenclature:
- Butane (alkane with 4 carbon atoms)
- Pentane (alkane with 5 carbon atoms)
- Nonane (alkane with 09 carbon atoms)
- Dodecane (alkane with 12 carbon atoms)
- Isooctane (branched alkane)
Ball and stick model of pentane
Alkene nomenclature:
Alkenes are a type of hydrocarbon that contains a carbon-carbon double bond. They use the olefin, as it shows that any hydrocarbon contains one or more double bonds.
The steps of preparing the nomenclature of alkenes are :
1. Alkenes are named using the same rules used in alkanes. The suffix will be -one.
2. The parent structure will be the longest chain which contains both carbon atoms of the double bond.
3. If the double bond is not terminal, the carbon should be numbered to give the first of the two double-bonded carbons the lowest possible number.
4. If there is more than one double bond present, the bonds will be numbered in the name of the molecule.
Examples of alkyne nomenclature:
- ethyne (alkene with 2 carbon atoms)
- propene (alkene with 3 carbon atoms)
- 1-Butene (alkene with 4 carbon atoms)
- 1-Pentene (alkene with 5 carbon atoms)
- 3-Dodecene (alkane with 12 carbon atoms, and double bond on the third carbon atom.)
https://embed.molview.org/v1/?mode=balls&cid=8004 (Ball and stick model of 1-pentene)
Alkyl nomenclature
It is the group where the substituent is attached to other molecular fragments. They are derived from alkanes by losing their hydrogen atoms.
The nomenclature done for the alkyl groups are :
•The alkyl group uses the -yl symbol as a suffix. If hydrogen is removed from one of the terminals, the alkyl group will be named n-propyl
•If one of the terminal carbon loses a hydrogen atom, it will be named n-butyl and if it was removed, then it will be named as sex – butyl
•If the hydrogen was removed from C, then the name will be tert – butyl. If it is losing the hydrogen atoms, then it will be named as iso – butyl.
Examples of alkyl nomenclature:
- Ethyne
- Propyne
- Pentyne
- Hexyne
