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),^[1] 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
Preferred IUPAC name 21-Methyl-11,21:22,31-tercyclopropane
Other names 1-Methyl-1,2-dicyclopropylcyclopropane; Sintin; Synthin; Tsycklin; Tsiklin
Identifiers
CAS Number	93223-46-2 Y
3D model (JSmol)	Interactive image
ChemSpider	452765 Y
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 N Key: GTKAAVZEFUFXDD-UHFFFAOYSA-N 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). N verify (what is YN ?) Infobox references

Syntin was used in the Soviet Union and later Russia as fuel for the Soyuz-U2 rocket from 1982 until 1995.^[2][3]

It was first synthesized in the USSR in 1959^[1] 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. On September 3, 1995, Soyuz TM-22, the seventy-first and last Soyuz-U2 rocket launched, being the last rocket fueled with Syntin.^[3]

Stereoisomers

Syntin has two stereocenters at the central cyclopropane ring. Thus, four stereoisomers exist:

Four Syntin Stereoisomers

In practice, syntin is used as a racemic mixture (a mixture where all stereoisomers are present in equal amounts).

See also

• Dicyclopentadiene