source: Master Organic Chemistry
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Rules:IUPAC of unsaturated aliphatic hydrocarbons-
i) Longest chain
The longest chain of carbon atom (parent chain) is selected as that all double & triple bonds must be present in parent chain even it is not the actual longest chain.
ii) A primary suffix is added to the root word to indicate the presence of double or triple bond in the parent chain.
For one double bond= Root word +ene
for one triple bond = root word+yne
If parent chain contains two or more double bonds (or triple bonds) the prefixes di, tri, tetra etc. are used before primary suffix .
for two double bonds = Root word + diene
for two triple bonds = Root word + diyne
iii) Numbering of C-Chain-
a) The parent chain is numbered in a way that lowest number is given to that carbon atom linked by double or triple bond.
b) If alkyl groups are present then preference should be given to double or triple bond because in priority table multiple bond is placed above than alkyl group.
c) The position of multiple bond is indicated by the number of the first carbon atom involved in the multiple bond. The number may be indicated either just before the root word or before the primary suffix.
iv) Alkyl groups or other substituents are numbered , named & placed in alphabetical order.
v) If both double & triple bonds are situated at identical position in relation to the end of parent chain, then double bond is given the preference over the triple bond.
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