Neopentane

• 2,2 - dimethylpropane (IUPAC)
• Dimethylpropane
• R601b

Colorless gas

Gaseous

0.60 g · cm -3 (liquid, the boiling point )

-16.6 ° C

9.5 ° C

0.15 MPa ( 20 ° C)

Practically insoluble in water (33 mg · l-1 at 20 ° C)

1.3476 (6 ° C )

Risk

1000 ml · m-3, 3000 mg · m-3

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Neopentane is the common name of 2,2- dimethylpropane, n-pentane and isopentane in addition one of the three structural isomers of pentanes with the formula C5H12. Neopentane is the simplest hydrocarbon with a quaternary carbon atom. At room temperature and atmospheric pressure neopentane is a colorless, highly flammable gas. Commercially, it is sold in liquefied compressed gas cylinders.

Representation and extraction

Neopentane is found in nature only in very small amounts in crude oil or natural gas in front, so that a recovery from it is not worth it. The synthesis is accomplished by methylation of tert- butyl compounds such as tert- butyl iodide or by means of dimethyl tert- Butylmagnesiumiodid by dimethyl sulfate, and by the hydrolysis of neopentylmagnesium with water.

Properties

Physical Properties

Neopentane shows, in comparison to the other pentanes a substantially higher melting point at 16.6 ° C. In addition, at -132.7 ° C a polymorphic phase transition with a transition enthalpy of 2.6305 kJ · mol -1 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 in a mesomorphic state before. The behavior is analogous to form similar " spherical " molecules such as tetramethyl butane, Cuban or adamantane, similar mesophases. The compound boils at atmospheric pressure at 9.5 ° C. It is in water with 33 mg / l only very poorly soluble. The compound is soluble in ethanol, diethyl ether, carbon tetrachloride, as well as in most of the aliphatic hydrocarbons.

Thermodynamic properties

The vapor pressure function is given by Antoine corresponding log10 (P) = A- ( B / ( T C )) ( P in bar, T in K) with A = 3.28533, B = C = -70.679 695.152 and in the temperature range of 205.6 K to 293.2 K, with A = 3.86373, B = 950.318 and C = -36 329 in the temperature range from 268 K to 313.2 K. and A = 4.61616, B = 1478.868 and C = 41 256 in the temperature range of 343 K to 433 K.

The temperature dependence of the enthalpy of vaporization can be determined according to equation ΔVH0 = A · e ( - βTr ) (1- Tr) β ( ΔVH0 in kJ / mol, Tr = (T / Tc) reduced temperature ) with A = 36.76 kJ / mol, β = 0.2813 and Tc = 433.8 K describe the temperature range between 264 K and 303 K.

Safety characteristics

The compound forms flammable gas - air mixtures. The explosion range is between 1.3 vol % (40 g/m3) as the lower explosive limit ( LEL) and 7.5 % by volume (230 g/m3 ) and upper explosive limit (UEL ). The ignition temperature is 450 ° C. The fabric falls within the temperature class T2.

Chemical Properties

Neopentane is not very reactive. Neopentylkationen, which are obtainable by the action of acid from neopentyl alcohol, go to a Wagner -Meerwein rearrangements.

Use

The compound can be used as the standard in NMR spectroscopy. Rarely neopentane is used as a component of propellants in spray cans or as a refrigerant ( R601b ).