4-Octyne
4-Octyne, also known as dipropylethyne, is a type of alkyne with a triple bond at its fourth carbon. Its formula is C8H14.
4-Octyne forms with 5-decyne, 3-hexyne, and 2-butyne a group of symmetric alkynes.
Preparation
One method for synthesizing 4-octyne is the reaction between acetylene and two equivalents of 1-bromopropane. Acetylene is first deprotonated by a base to give an anion, which then undergoes nucleophilic substitution with the bromopropane. The resulting alkyne is again deprotonated and reacts similarly with a second molecule of bromopropane. This reaction can be carried out in liquid ammonia at −70 °C with sodium amide as the base.Another synthetic route is the elimination reaction of 4,5-dibromooctane, which can be done in similar conditions.