Why is 1 3 butadiene so toxic



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Structural formula
General
Surname Butadiene
other names
  • 1,3-butadiene
  • Pyrrolylene
  • 1,3-butadiene - 1,3-butadiene
  • Biethylene - diethylene - diethene
  • Bivinyl - divinyl
  • Vinylethylene - vinylethene
  • Erythren
Molecular formula C.4H6
CAS number 106-99-0
Brief description colorless gas with an aromatic odor[1]
properties
Molar mass 54.09 g mol−1
Physical state gaseous
density 2.4982 kg m−3 (0 ° C)[1]
Melting point −108.92 ° C[1]
boiling point −4.5 ° C[1]
Vapor pressure

239.8 kPa (20 ° C)[1]

solubility

Slightly soluble in water: 1 g · l−1 (20 ° C)[1]

safety instructions
WGK 2 - hazardous to water
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions.

Butadiene (Vinyl ethylene) is a colorless gas with a mild, aromatic odor. It is an unsaturated hydrocarbon of which two isomers exist: 1,3-butadiene (of great industrial importance) and the more difficult to manufacture and far less important 1,2-butadiene. The 1,3-butadiene has 2 conjugated double bonds and is therefore a diene.

Isoprene (2-methyl-1,3-butadiene) is a derivative of butadiene.

properties

The odor threshold of butadiene is 4 mg / m3. The gas can be easily liquefied. The gas is only slightly soluble in water (1.03 g / l at 20 ° C). Butadiene is heavier than air.

Butadiene is flammable and polymerizes easily, which is why a stabilizer, for example 4-tert-butyl catechol (TBC), is usually added to the butadiene.

Conjugated double bonds in 1,3-butadiene

In the planar molecule, all four carbon atoms are sp2-Hybridized. The π orbitals overlap above and below the molecular plane. π bonds are created by overlapping the 1st and 2nd carbon atoms and the 3rd and 4th carbon atoms. In addition, the orbitals of the 2nd and 3rd carbon atoms can overlap so that the π electrons can spread over the entire molecule. The electrons are delocalized. Because electrons are distributed over a larger space, an increased stability is observed in 1,3-butadiene. The influence of these conjugated double bonds is evident in polymerization reactions with butadiene: If the attack occurs on the 1st carbon atom, the linkage is not made with the 2nd carbon but with the fourth. Instead, a “new” double bond is formed between the 2nd and the third atom.

Manufacturing

Butadiene is produced by splitting off hydrogen from saturated hydrocarbons through vigorous heating (cracking).

use

More than 90 percent of butadiene production is processed into synthetic rubber. Another application is ABS, a copolymer made from acrylonitrile, butadiene and styrene. In addition, butadiene and hydrogen cyanide are used to make adiponitrile, which is an intermediate product in the production of polyamides. Hydroxyl-terminated poly-butadiene, HTPB, a rubbery solid, is used as fuel in hybrid missiles such as the SpaceShipOne. HTPB has the advantage that it is non-toxic, non-explosive and difficult to ignite. In the solid fuel boosters of the Space Shuttle and the Ariane 5, HTPB is used as a binder and fuel, together with aluminum powder and ammonium perchlorate. However, this mixture is much more dangerous than pure HTPB.

Historical

The polymer produced from butadiene and the catalyst sodium Buna (ButadienN / Atrium) was of great importance for the German armaments and war economy before and during the Second World War.

hazards

Butadiene is carcinogenic, extremely flammable and toxic. It forms explosive mixtures between an air volume fraction of 1.4 to 16.3 percent. Butadiene has a narcotic effect.

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  1. abcdef Entry on butadiene in the GESTIS substance database of the BGIA, accessed on December 9, 2007 (JavaScript required)

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