Triethylaluminium

• Triethylaluminum
• TEA

Colorless to yellowish liquid

Liquid

0.8324 g · cm -3 ( 25 ° C)

-50.7 ° C

187 ° C.

4 hPa (at 20 ° C)

Violent decomposition in water

Risk

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Triethylaluminum, also referred to as TEA or triethylaluminum (ATE ) is an organometallic compound of aluminum. The compound is pyrophoric and can ignite on contact with the air itself. With water TEA reacts extremely violently to aluminum hydroxide and ethane. TEA is due to the electron- hole to the aluminum atom which has only six valence, a Lewis acid.

Representation and extraction

The technical synthesis is carried out by reacting aluminum, hydrogen and ethene, with a starting amount of triethylaluminum is necessary. Aluminum alone does not react directly with hydrogen. In the presence of triethyl aluminum is formed as an intermediate diethylaluminum hydride, which gives the target compound with ethene.

The sum equation then

The synthesis can be carried out as a continuous two-stage process, wherein a part of the triethyl aluminum is recirculated.

A second synthesis variant is based on the reaction of aluminum with ethyl chloride, ethyl aluminum where the first is obtained.

A reduction reaction with sodium then gives the target compound.

Properties

Physical Properties

Triethylaluminum is a pyrophoric, colorless to yellowish liquid. At atmospheric pressure, the compound boils at 187 ° C. The enthalpy of vaporization is 73.2 kJ · mol here -1. The vapor pressure function is given by Antoine corresponding log10 (P) = A- ( B / ( T C )) ( P in bar, T in K) with A = 7.41394, B = 3451.295 and C = 2.14 in the temperature range of 330 K to 399 K. the melting point of the compound is at -50.7 ° C. The heat of fusion is 10.6. kJ · mol -1 The triple point is at -48 ° C and 1.7 · 10-5 mbar.

Chemical Properties

In solid or liquid state is triethylaluminum as dimer, in the gas phase, however, in monomeric form. ( - Alkali metal ion and X - M halide, cyanide) with alkali halides and cyanides 1:1 complex of the type M [( C2H5) 3AlX ] and 1:2 complexes of the type M [( C2H5) 6Al2X ] are formed. The entry of solid anhydrous aluminum halides in triethylaluminum result depending on the stoichiometry of the corresponding Diethylaluminiumhalogenide or Ethylaluminiumdihalogenide.

A real transalkylation succeed in the reaction with zinc chloride to give the desired diethyl diethyl aluminum chloride by -product can be removed by distillation.

With oxygen, the Aluminiumtriethanolat is formed in a free radical chain reaction at the aluminum -to-carbon bonds. This reaction is very highly exothermic with a reaction enthalpy of -1017 kJ · mol -1, so that an appropriate response control over the supply of oxygen is necessary to avoid uncontrolled spontaneous combustion processes.

Triethylaluminum reacts readily and violently with protic substances, such as mineral acids, water, alcohols, mercaptans, phenols, carboxylic acids, ammonia, amines, acetylene and monosubstituted acetylenes.

Use

Triethyl aluminum as a component of Ziegler-Natta catalysts used in industrial scale cocatalyst for polyolefin; especially of polyethylene and polypropylene. In the so-called Alfol TEA process for the synthesis of higher unbranched primary alcohols ( " fatty alcohols " ) from ethene used.

In MOCVD and MBE systems triethylaluminum is used as the reaction medium for the deposition of III-V semiconductor layers, for example, LEDs.

In war weapons, such as flamethrowers, triethylaluminum ( thickened pyrophoric agent TPA, engl. ) Is as liquid fire means or with thickeners such as polyisobutylene as a yellow border fabric used. In principle, such weapons can be considered as the successor of napalm. Regarding the combustion temperature and the incendiary effect they surpass this. TEA itself can not be extinguished with water, since it reacts explosively with water. If it fights with other extinguishing agents, as may at any time contact with the air again, spontaneous combustion use.

Safety

The vapors of triethylaluminum is very irritating and corrosive to the mucous membranes. With up to two days delay may occur edema. Often the so-called fume fever is observed. If exposed to the skin very painful and slow-healing wounds may arise.