Pentene isomers (also called amylene) are hydrocarbons with a molecular formula of C 5 H 10 that have a C = C double bond. Thus, they belong to the group of alkenes. There are five constitutional amylenes, of which the penten-2-isomer may be present as a cis or trans isomer. Amylene is present as a mixture of isomers in cracking gases and in natural gas. Another constitutional substance is cyclopentene, which, however, is not pentene.
Structure
A change in the position of the double bond in the alkene leads to another isomer. Butene and pentene exist as different isomers.
C 5 H 10 is represented by a pentene-1 (α-amylene) molecule, which has the structural formula:
Other structural isomers of pentene can be altered by changing the site of the double bond or the manner in which carbon atoms are bonded to each other.
Other isomers are cis-penten-2 (cis-β-amylene) and trans-penten-2 (trans-β-amylene), represented by the structural formula:
2-methyl-1-butene can be obtained by catalytic or steam cracking of oil, followed by separation of the C 5 fraction, as well as extraction with cold aqueous sulfuric acid. Used as a solvent in organic synthesis. It is also used in the production of pinacolone, flavor enhancers, spices, pesticides and tertiary amylphenol. Represented by the structural formula:
3-methyl-1-butene can be obtained by oil cracking. It is also possible to obtain from 3-methyl-1-butanol using aluminum-containing oxide. Used to obtain other chemical compounds, for example, linderin A or polymers. Represented by the structural formula:
2-methyl-2-butene can be obtained by dehydration from neopentanol. Used to obtain 3-bromo-2,3-dimethyl-1,1-dicyano-butane in the presence of 2,2'-azobis (2,4-dimethyl-4-methoxyvaleronitrile) as a catalyst. Represented by the structural formula:
Here, the double lines between carbon atoms represent a double covalent bond, and single lines represent single covalent bonds.
Note that each carbon atom (C) has four bonds (valency 4), and each hydrogen atom (H) has one bond (valency 1). Valence is the unifying force of an atom.
Table: Pentene vapor pressure functions
Substance | T (K) | A | B | C |
penten-1 (α-amylene) | 285.98-303.87 | 3,91058 | 1014,294 | −43,367 |
cis-pentene-2 (cis-β-amylene) | 274.74–342.03 | 3,99984 | 1069,229 | −42.393 |
trans-penten-2 (trans-β-amylene) | 274.18–341.36 | 4,03089 | 1084,165 | −40,158 |
2-methylbutene-1 (γ-isoamylene) | 274.30–335.82 | 3.98652 | 1047,811 | −41.089 |
3-methylbutene-1 (α-isoamylene) | 276.19–343.74 | 4,04727 | 1098,619 | −39.889 |
and 2-methylbutene-2 (β-isoamylene) | 273.37–324.29 | 3.95126 | 1013,575 | −36.32 |
Pentene isomers are fluids with high vapor pressure, moderate solubility in water and low molecular weight (70,13), which indicates the ability of absorption through the lungs and is widely distributed in the body.
Due to the low boiling point of the isomers, low cost and relative safety, they are used in geothermal power plants as a working medium.
Getting
Pentene isomers are components of coal tar, shale oil, cracked gases and cracked gasoline and can be obtained by fractional distillation. Rubber pyrolysis forms, among other things, 2-methyl-1-butene and 2-methyl-2-butene.
Pentenes are formed by dehydration (removal of water) from pentenols - the so-called amyl alcohols. Thus, pentene (the so-called fuselolamylene) is obtained from fusel oils.
Using
Pentene isomers are used for the synthesis of amylphenols, isoprene and pentenols, as well as for polymerization. In addition, amylenes are added as stabilizers to chloroform and dichloromethane to remove phosgene released by air and light.
According to the Hazardous Substances Data Bank (HSDB 2002), 1-pentene is mainly used in organic synthesis as a mixing agent for high-octane motor fuels and in pesticide formulations. 2-pentene is used as an inhibitor of polymerization in organic synthesis. In high concentrations, it causes respiratory and cardiac depression in animals, while in humans it can cause arousal.
Impact on human and animal health
Acute toxicity studies in animals or humans with adequate dose-response data are not available for pentene isomers. Studies have shown the effect for mixing flows of petroleum distillates. However, the distillate is a mixture of compounds, which makes it impossible to differentiate the effects of specific chemicals. The only data on acute toxicity for pentene are LC50 data, the concentrations of which turned out to be lethal for 50% of the study samples: 4-hour (h) LC50 in rats - 175,000 mg / m 3 and 2 hours of LC50 in mice -180 000 mg / m 3 . These LC50 doses are relatively high and indicate that the substance has low acute lethal toxicity.
The minimum assessment database was not met, therefore procedures for limited toxicity data were used. Two methods were investigated: an approach with a NOAEL ratio (no adverse effect level) -c-LC50 was observed and an analog approach. An analogue is defined as a chemical compound that is structurally similar to another compound, but slightly different in composition (as when replacing one atom with an atom of another element or in the presence of a certain functional group). To use this approach, there must be an unambiguous structural and metabolic relationship between the chemical LTD and the chemical with toxicity information.
There are no studies available that describe the potential chronic toxicity of any pentene isomer. Since they have limited data on LTD. Chronic ESL for pentene was obtained using an analogue chemical approach using toxicity information for butene isomers, similar to the approach for developing acute ESL.