Pentene isomers (also called amylene) are hydrocarbons with the molecular formula C5H10, which have a C=C double bond. Thus, they belong to the group of alkenes. There are five constitutional amylenes, of which the pentene-2 isomer may be present as the cis or trans isomer. As a mixture of isomers, amylenes are present in cracking gases and in natural gas. Another constitutional substance is cyclopentene, which, however, is not pentene.
Structure
Changing the position of the double bond in the alkene leads to another isomer. Butene and pentene exist as different isomers.
C5H10 is represented by the pentene-1 (α-amylene) molecule, which has the structural formula:
Other structural isomers of pentene can be changed by changing the location of the double bond or the way the carbon atoms are connected to each other.
Other isomers are cis-pentene-2 (cis-β-amylene) and trans-pentene-2 (trans-β-amylene), represented by the structural formula:
2-methyl-1-butene canobtained by catalytic or steam cracking of oil, followed by separation of the C5 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 produced by oil cracking reaction. It is also possible to obtain from 3-methyl-1-butanol using an aluminum oxide. It is used to obtain other chemical compounds, such as 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, 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 (valence 4), and each hydrogen atom (H) has one bond (valence 1). Valence is the unifying force of the atom.
Table: pentene vapor pressure functions
| Substance | T (K) | A | B | C |
| pentene-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-pentene-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 liquids with high vapor pressure, moderate water solubility and low molecular weight (70, 13), indicating the ability to be absorbed through the lungs and widely distributed in the body.
Due to the low boiling point of the isomers, low cost and relative safety, they are used ingeothermal power plants as a working environment.
Receive
Pentene isomers are components of coal tar, shale oil, cracked gases and cracked gasoline and can be obtained by fractional distillation. The pyrolysis of rubber produces, among others, 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 fuselamylene) is obtained from fusel oils.
Use
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 from air and light.
According to the Hazardous Substances Data Bank (HSDB 2002), 1-pentene is primarily used in organic synthesis as a blending agent for high octane motor fuels and in pesticide formulations. 2-Pentene is used as a polymerization inhibitor in organic synthesis. In high concentrations, it causes respiratory and cardiac depression in animals, while it can cause agitation in humans.
Impact on human and animal he alth
Acute toxicity studies in animals or humans with adequate dose-response data are not available for pentene isomers. The studies carried out demonstrate the effect for oil distillate blending streams. However, the distillate is a mixture of compounds, making it impossible to differentiate the effectsspecific chemicals. The only data on acute toxicity for pentene are LC50 data, which were lethal in 50% of the study samples: 4-hour (h) LC50 in rats is 175,000 mg/m3, and 2 -x hours LC50 in mice -180,000 mg/m3. These LC50 doses are relatively high and indicate that the substance has low acute lethal toxicity.
The minimum database for evaluation was not met, so procedures for limited toxicity data were used. Two methods were investigated: the NOAEL (no observed adverse effect level)-to-LC50 approach and the analog approach. An analog is defined as a chemical compound that is structurally similar to another compound but slightly different in composition (as in the replacement of one atom by an atom of another element, or the presence of a specific functional group). To use this approach, there must be unambiguous structural and metabolic relationships between the LTD chemical and the chemical with toxicity information.
There are no studies available that describe the potential chronic toxicity of any pentene isomer. Because they have limited data on LTD. Chronic ESL for pentene was derived from an analog chemistry approach using toxicity information for butene isomers similar to the approach for developing acute ESL.
