4-Octyne, also known as dipropylethyne, is a type of

alkyne \ce \ce Acetylene \ce \ce \ce Propyne \ce \ce \ce \ce 1-Butyne In organic chemistry, an alkyne is an unsaturated hydrocarbon containing at least one carbon—carbon triple bond. The simplest acyclic alkynes with only one triple bond and n ...

with a

triple bond A triple bond in chemistry is a chemical bond between two atoms involving six bonding electrons instead of the usual two in a covalent single bond. Triple bonds are stronger than the equivalent single bonds or double bonds, with a bond order o ...

at its fourth

carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with o ...

(the '4-' indicates the location of the triple bond in the chain). 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 Acetylene (systematic name: ethyne) is the chemical compound with the formula and structure . It is a hydrocarbon and the simplest alkyne. This colorless gas is widely used as a fuel and a chemical building block. It is unstable in its pure ...

and two equivalents of 1-bromopropane. Acetylene is first deprotonated by a base to give an anion, which then undergoes

nucleophilic substitution In chemistry, a nucleophilic substitution is a class of chemical reactions in which an electron-rich chemical species (known as a nucleophile) replaces a functional group within another electron-deficient molecule (known as the electrophile). The ...

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 Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous was ...

at −70 °C with

sodium amide Sodium amide, commonly called sodamide (systematic name sodium azanide), is the inorganic compound with the formula . It is a salt composed of the sodium cation and the azanide anion. This solid, which is dangerously reactive toward water, is whit ...

as the base. Another synthetic route is the

elimination reaction An elimination reaction is a type of organic reaction in which two substituents are removed from a molecule in either a one- or two-step mechanism. The one-step mechanism is known as the E2 reaction, and the two-step mechanism is known as the E1 ...

of 4,5-dibromooctane, which can be done in similar conditions.

Properties

4-octyne is a colorless liquid at room temperature. Its density at 25 °C and otherwise stable conditions is 0.751 g/mL. The

boiling point The boiling point of a substance is the temperature at which the vapor pressure of a liquid equals the pressure surrounding the liquid and the liquid changes into a vapor. The boiling point of a liquid varies depending upon the surrounding envir ...

is 131–132 °C. The average

molar mass In chemistry, the molar mass of a chemical compound is defined as the mass of a sample of that compound divided by the amount of substance which is the number of moles in that sample, measured in moles. The molar mass is a bulk, not molecular, p ...

is 110.20 g/mol.

References

External links

* {{DEFAULTSORT:Octyne, 4- Alkynes