Syntin

Colorless liquid

0.8504 g · cm -3

158 ° C.

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Syntin is a rocket fuel on the basis of a hydrocarbon with molecular formula C10H16, which contains three highly strained cyclopropane rings.

Representation and extraction

The synthesis of Syntin occurs in a multistep synthesis sequence are in the formed and links the Cyclopropyleinheiten. The starting compound the Hydroxypropylmethylketon can be used, from which, after conversion to the chloride by nucleophilic substitution and subsequent cyclization under mildly basic conditions with the cyclopropylmethylketone the first cyclopropyl moiety is formed. A subsequent dimerization in the presence of aluminum tri- tert-butoxide, gives the 1,3 - dicyclopropyl -2-buten -1-one. By reaction with hydrazine hydrate to obtain the 3,5- dicyclopropyl -5-methyl -4 ,5-dihydro -1H-pyrazole. This is the central cyclopropyl ring and thus the target compound is formed by distillation over potassium hydroxide at 190 ° C under nitrogen elimination. From the synthesis results in a mixture of isomers.

A separation of the isomers can be done by preparative chromatography.

Properties

Syntin is a colorless liquid, boiling as an isomer mixture at atmospheric pressure and 158 ° C. Under reduced pressure of 49 Torr, a boiling point of 80 ° C is observed. Because of the three highly strained cyclopropane rings the molecule has a high enthalpy of formation of ΔfH ° (l) = 131.6 kJ · mol -1 and 966 kJ / kg -1 for the trans isomer and ΔfH ° (l) = 134.1 kJ · mol -1 and 984 kJ / kg -1 for cis- isomer. It therefore is an endothermic compound with a high heat of combustion of -6353.7 kJ · mol -1 for the trans isomer and -6355.9 kJ · mol -1 for the cis isomer. The advantages over conventional hydrocarbons such as RP- 1 consist in the greater density, lower viscosity and larger heat of combustion.

Stereochemistry

Syntin contains two stereogenic centers on a cyclopropane ring, so that two transport and two cis isomers exist. In practice, the mixture of the four stereoisomers are relevant:

Use

Syntin was used in the Soviet Union and in Russia in the 1980s and 1990s as a fuel for the Soyuz rocket and the Buran. It was first synthesized in the USSR in 1960, and in the 1970s began mass production. It was prepared in a multistep synthetic process from ordinary hydrocarbons. After the collapse of the Soviet Union the production of this substance was too expensive and was therefore set.