Alkynes: Nomenclature of Hydrocarbon Compounds

University:
Colorado State University
Course:
CHEM 107 | Fundamentals of Chemistry (GT-SC2)
Academic year:

2023
Views:

77

Pages:

2
Author:

Hizkia L

Nomenclature of Hydrocarbon Compounds : Alkynes a. General formula Alkynes are unsaturated aliphatic hydrocarbon compounds contains a triple bond. Consider the following example. What is the general formula for alkynes? Do you still remember the alkadiene compound? Look at the structural formulas of the compounds below! What is the number of C and H atoms in the two compounds above? It turns out that alkynes with 4 C atoms have 6 H atoms, while alkenes with 4 C atoms have 8 H atoms. So, the general formula for alkynes is: Cn H2n – 2 b. Alkun Nomenclature 1) Straight chain alkynes have the same name as alkanes, only the ending "ana" is replaced with "una". Example: C3 H4 : propuna C5 H8 : tuna C4 H6 : butuna 2) Branched chain alkynes. The naming sequence is: a) Choose the parent chain, namely the longest carbon chain contains a triple bond. Example: b) Alkyne numbering starts from one end of the parent chain, so that the C atom with the triple bond gets the smallest number. Example: c) Naming, in the following order: • C number that binds the branch • name of the branch • C number that has a triple bond • name of the main chain (alkyne) Example : c. Alkyne isomerism Alkynes only have structural isomerism, not geometric isomerism (why?). Alkyne isomers start from C4 H6 . Example: 1) C4 H6 has two isomers, namely: 2) C5 H8 has three isomers, namely: d. Alkyne properties 1) Physical. Properties The physical properties of alkynes are the same as those of alkanes and alkenes. 2) Chemical Properties (Alkyne Reaction). nThe reactions with alkynes are similar to alkenes, differing only in the amount of reactant required to saturate the double bond. Alkynes require twice the amount of reactants required to the alkene for the same number of double bonds.