Syntin

Syntin is a hydrocarbon with the molecular formula C₁₀H₁₆ used as a rocket fuel. It is a mixture of four stereoisomers (see below). It has a density of 0.851 g/mL, and a boiling point of 158 °C. Due to the presence of three strained cyclopropane rings, the molecule has a highly positive enthalpy of formation: Δ_fH°(l)= 133 kJ/mol (980 kJ/kg, the average value for the isomeric mixture), bringing additional energy into the combustion process. It has advantages over the traditional hydrocarbon fuels, such as RP-1, due to higher density, lower viscosity and higher specific heat of oxidation.

Syntin

Names
IUPAC name 1′-Methyl-1,1′:2′,1′′-tercyclopropane
Other names 1-Methyl-1,2-dicyclopropylcyclopropane; Sintin; Synthin; Tsycklin
Identifiers
CAS Number	93223-46-2
3D model (JSmol)	Interactive image
ChemSpider	452765
PubChem CID	519050
CompTox Dashboard (EPA)	DTXSID90333879
InChI InChI=1S/C10H16/c1-10(8-4-5-8)6-9(10)7-2-3-7/h7-9H,2-6H2,1H3 Key: GTKAAVZEFUFXDD-UHFFFAOYSA-N InChI=1/C10H16/c1-10(8-4-5-8)6-9(10)7-2-3-7/h7-9H,2-6H2,1H3 Key: GTKAAVZEFUFXDD-UHFFFAOYAR
SMILES CC1(C2CC2)C(C3CC3)C1
Properties
Chemical formula	C10H16
Molar mass	136.238 g·mol^−1
Density	0.851 g/mL
Boiling point	158 °C (316 °F; 431 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Syntin was used in the Soviet Union and later Russia in 1980s-1990s as fuel for the Soyuz-U2 rocket. It was first synthesized in the USSR in the 1960s and brought to mass production in the 1970s. It was prepared in a multi-step synthetic process from easily obtained acetylcyclopropane(the 3rd molecule):

Syntin synthesis 01

After dissolution of the USSR, the production of this fuel was halted due to the expense of the synthesis.

Stereoisomers

Syntin is a molecule with two stereocenters at the central cyclopropane ring. Thus, the following four stereoisomers may exist:

Four Syntin Stereoisomers

In practice, the fuel has been used as mixture of all four stereoisomers.

See also

• dicyclopentadiene

References

• A. P. Mesheheryakov, V. G. Glukhovtsev, A. D. Petrov, “Synthesis of 1-methyl-1,2-dicyclopropylcyclopropane”, Doklady Akademii Nauk SSSR, 1960, 130, 779-81.
• Yu. P. Semenov, B. A. Sokolov, S. P. Chernykh, A. A. Grigor'ev, O. M. Nefedov, N. N. Istomin, G. M. Shirshov, “Multiple strained-ring alkane as high-performance liquid rocket fuel”, RU 2233385, C2 20040727.
• T. Edwards, “Liquid Fuels and Propellants for Aerospace Propulsion: 1903-2003”, Journal of Propulsion and Power, 2003, 19(6), 1089-1107.
• V. Azov, D. Vorontsov, "The last battle of hydrocarbons?", Novosti Kosmonavtiki, 2008, 18, No. 2 (301), 44-46.