4-Octyne

4-Octyne, also known as dipropylethyne, is a type of alkyne with a triple bond at its fourth carbon (the '4-' indicates the location of the triple bond in the chain). Its formula is C8H14.

4-Octyne
Names
Preferred IUPAC name
Oct-4-yne
Other names
  • Dipropylacetylene
  • 1,2-Dipropylacetylene
  • Dipropylethyne
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.016.119
EC Number
  • 217-730-2
UNII
  • InChI=1S/C8H14/c1-3-5-7-8-6-4-2/h3-6H2,1-2H3
    Key: GZTNBKQTTZSQNS-UHFFFAOYSA-N
  • InChI=1/C8H14/c1-3-5-7-8-6-4-2/h3-6H2,1-2H3
    Key: GZTNBKQTTZSQNS-UHFFFAOYAB
  • CCCC#CCCC
Properties
C8H14
Molar mass 110.200 g·mol−1
Appearance colorless liquid
Density 0.751 g/mL
Melting point −103 °C (−153 °F; 170 K)
Boiling point 131–132 °C (268–270 °F; 404–405 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

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.[1]

Another synthetic route is the elimination reaction of 4,5-dibromooctane, which can be done in similar conditions.[2]

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 is 131–132 °C. The average molar mass is 110.20 g/mol.[3]

References
  1. Seifert, H. (1948-05-01). "Olefinsynthesen in der C6- bis C11-Reihe". Monatshefte für Chemie und verwandte Teile anderer Wissenschaften (in German). 79 (3): 198–215. doi:10.1007/BF00899394. ISSN 1434-4475.
  2. Miller, Harold N.; Greenlee, Kenneth W.; Derfer, John M.; Boord, Cecil E. (1954). "Mono- and Di-Alkylacetylenes from Vicinal Dihalides and Sodium Amide in Liquid Ammonia1". The Journal of Organic Chemistry. 19 (12): 1882–1888. doi:10.1021/jo01377a003. ISSN 0022-3263.
  3. Lide, David R. (2010). "Physical Constants of Organic Compounds". CRC Handbook of Chemistry and Physics (90th ed.). Boca Raton, FL: CRC Press/Taylor and Francis. pp. 3–406.
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