Methyl tert-butyl ether
- Tert-butylmethylether ( tBME )
- Methyl tertiary butyl ether (MTBE)
- 2-methoxy- 2-methylpropane
- Plus -minus- ether
Colorless, volatile liquid
Liquid
0.74 g · cm -3 ( 20 ° C)
-109 ° C
55 ° C.
270 hPa ( 20 ° C)
- Poorly in water ( 42 g · l-1 at 20 ° C)
- Well in many organic solvents
1.3664 (25 ° C)
Risk
180 mg · m- 3, 50 ml · m-3
Template: Infobox chemical / molecular formula search available
MTBE ( methyl tert- butyl ether ), according to IUPAC 2-methoxy -2-methyl propane is an aliphatic ether having on the one hand because of its use as an additive in gasolines, as well as on the other hand as a solvent in organic chemistry achieved a certain industrial significance.
Physical Properties
MTBE is a colorless, typically ethereal smelling liquid. The compound boils at atmospheric pressure at 55 ° C. The melting point is at -109 ° C. The miscibility with water is limited: In 100 g of water dissolve at room temperature a maximum of 4.8 g of MTBE, conversely, dissolve in 100 g of MTBE maximum of 1.4 g of water. The azeotrope with water boiling at atmospheric pressure at 52.9 ° C with an azeotrope of 96.5 % MTBE and 3.5 % water ( by mass). With methanol boiling azeotrope is at a level of 10 % by mass of a formed at 51 ° C.
Thermodynamic properties
The vapor pressure function is given by Antoine corresponding log10 (P) = A- ( B / ( T C)) (P in kPa, T in K), with A = 6.34991, B = 1312.52 and C = -26 03 in the temperature range of 315 K to 365 K.
The most important thermodynamic properties are listed in the following table:
The temperature dependence of the enthalpy of vaporization can be determined according to equation ΔVH0 = A · exp (- β · Tr ) (1- Tr) β ( ΔVH0 in kJ / mol, Tr = (T / Tc) reduced temperature ) with A = 46.23 kJ / mol, β = 0.2893 and Tc = 497.1 K describe the temperature range between 298 K and 343 K.
Temperature dependence of the heat of vaporization of MTBE
Safety characteristics
Tert- butyl methyl ether forms flammable vapor - air mixtures. The compound has a flash point of -28 ° C. The explosion range is between 1.6 vol% (58 g/m3) as the lower explosive limit ( LEL) and 8.4 % by volume (310 g/m3 ) and upper explosive limit (UEL ). A correlation of explosion limits with the vapor pressure function yields a lower explosion point of -33 ° C and an upper explosion point of -5 ° C. The marginal gap width was determined to be 1 mm. The result is thus a mapping in the explosion group IIA. The ignition temperature is 460 ° C. The fabric falls within the temperature class T1. The electrical conductivity is relatively low with 3.0 x 10-11 S · m -1.
According to the Dangerous Goods Regulations is MTBE Class 3 ( Flammable liquids ) with the Packing Group II (medium hazard ) associated with ( Label: 3 ).
Synthesis
MTBE is a large scale säurekatalytisiert from isobutene and methanol produced:
Use
118 RON, MON 101
-28 ° C
Tert- butyl methyl ether is added mainly as an anti-knock agents in petrol. Increasing the octane number, thereby resulting in a reduction of the susceptibility to knock of the gasoline engine. It replaced tetraethyl lead in unleaded fuels.
It is also found in so-called starter sprays that you can spray at start-up difficulties in the intake system of the engine.
MTBE is increasingly used in organic chemistry, as well as solvent extraction agent. It replaces ethers such as diethyl ether or tetrahydrofuran, because MTBE has a very low to no tendency to form peroxides. This is because at the quaternary carbon atom no peroxide can be formed ( since there is no hydrogen atom carries ) and a peroxide to the methylene group would proceed mechanistically via a very unstable, primary radical.
More information
It is discussed the environmental impact of MTBE particularly with regard to groundwater. In the U.S., there was contamination of drinking water due to tank leakage. The admixture is therefore banned in several U.S. states. The groundwater risk from fuel storage at service stations is considered, for example in Germany as a child, as used here, mostly double-walled underground tanks at gas stations. MTBE can be perceived even in small traces due to the intense smell. At present, in Germany increased ETBE ( bioethanol and isobutene ) used to meet the required Bio - blending quotas can (see also bioethanol).
The effects of MTBE on human health and the environment are tested under REACH in 2014 as part of the fabric rating of France.
Safety
Because of the high flammability should be always carried out with tert- butyl methyl ether in a fume hood. The skin should be protected from splashes by wearing gowns and suitable protective gloves. When filling large amounts, it is advisable to take measures against electrostatic charge (use of tin cans and funnels that are grounded).
- Inhalation: Remove exposed person to fresh air. The vapors may cause headaches and dizziness up to faint.
- In case of skin contact: Wash with soap and water. Intensive skin contact can cause the same symptoms as inhalation.
- In case of eye contact: Rinse thoroughly with water ( eyewash ).
- If swallowed: Rinse mouth with water. Call a doctor.