Tetramethylbutane

• 2,2,3,3 -tetramethyl butane
• Hexamethylethan

Colorless solid

Fixed

0.82 g · cm -3 ( 20 ° C)

100.8 ° C

107 ° C.

110 mbar ( 50 ° C)

0.7 mg · l-1

Risk

Template: Infobox chemical / molecular formula search available

Tetramethylbutane is the most branched isomer of Octane. The high degree of branching, resulting in comparison to more chain-like isomers to differing physical properties, such as a significantly higher melting point, such that the compound as the sole of octane isomers is present at room temperature as a solid.

Representation and extraction

The synthesis of tetramethyl butane is achieved by the combination of two tert- Butylfunktionen. In an early version of tert- butyl magnesium chloride representation is reacted with tert -butyl chloride. The Grignard compound can be formed in a one-pot variant in situ in the reaction of tert -butyl chloride with magnesium and implemented.

Dimerization of tert -butyl bromide or tert- butyl iodide can be carried out in the presence of activated copper. Another presentation option is the conversion of tertiary butyltrichlorosilane with tert -butyllithium.

Properties

Tetramethylbutane is a solid substance that occurs in two polymorphic crystalline forms at room temperature. At room temperature, the crystalline Form I is present, which turns at 100.8 ° C in the liquid phase. At -120.6 ° C and a phase transition of the crystal form II to form I is observed. Here, the transition from the crystalline to a plastically crystalline form. This means that the compound is above this temperature to the melting point and hence, even at room temperature in a mesomorphic state before. The behavior is analogous to similar " spherical " molecules such as Cuban or adamantane, which form similar mesophases. The boiling point of the compound is already at 107 ° C, so that the liquid phase exists only at atmospheric pressure in a temperature range of about 6 K. The Sublimationsdruckfunktion results after Antoine corresponding log10 (P) = A- ( B / ( T C )) ( P in bar, T in K) with A = 5.08335, B = 1724.764 and C = -38.383 in temperature range of 273 K to 338 K. the amount of transition enthalpies for the transition to crystal form II I ΔtrH = 2.00 kJ · mol -1 for the melt ΔmH = 7.54 kJ · mol -1, and the evaporation ΔbH = 42 91 kJ mol -1.