Pentenes

Pentenes (also called amylenes ) are hydrocarbons with the empirical formula C ₅ H ₁₀ that have a carbon-carbon double bond ( C = C double bond for short ). They therefore belong to the group of alkenes . There are five constitutional isomeric pentenes, of which 2- pentene can exist as a cis or trans isomer . Pentenes occur as a mixture of isomers in cracked gases and in natural gas . Another constitutional isomer is cyclopentane , which, however, is not pentene.

Structure and properties

Pentenes
Surname	Pent-1-en	cis -pent-2-ene	trans -pent-2-ene
other names	1-pentene, amylene	( Z ) -Pent-2-ene β-amylene	( E ) -pent-2-ene β-amylene
Structural formula
CAS number	109-67-1	627-20-3	646-04-8
		109-68-2 (mixture of isomers)
Molecular formula	C 5 H 10
Molar mass	70.13 g mol −1
Brief description	colorless, low-boiling, extremely flammable liquids
Melting point	−138 ° C	−151.4 ° C	−136 ° C
boiling point	30 ° C	36.9 ° C	36.3 ° C
solubility	insoluble in water, easily soluble in ethanol and ether
GHS labeling	danger
H and P phrases	224-304-315-319	225-304-315-319-335	224-304-315-319-335
	no EUH phrases	no EUH phrases	no EUH phrases
	210-301 + 310 305 + 351 + 338-331	210-261-301 + 310 305 + 351 + 338-331	210-261-301 + 310 305 + 351 + 338-331
Pentenes (continued)
Surname	2-methyl-1-butene	2-methyl-but-2-ene	3-methyl-1-butene
other names		Isopentes	2-methyl-but-3-ene
Structural formula
CAS number	563-46-2	513-35-9	563-45-1
Molecular formula	C 5 H 10
Molar mass	70.13 g mol −1
Brief description	colorless, low-boiling, extremely flammable liquids
Melting point	−137.5 ° C	−133.8 ° C	−169.5 ° C
boiling point	31.2 ° C	38.6 ° C	20.1 ° C
solubility	insoluble in water, easily soluble in ethanol and ether
GHS labeling	danger	danger	danger
H and P phrases	224-304	225-302	224-304-315-319-335
	no EUH phrases	no EUH phrases	no EUH phrases
	210-301 + 310-331	210	210-261-301 + 310-305 + 351 + 338-331

According to Antoine, the vapor pressure functions result from log ₁₀ (P) = A− (B / (T + C)) (P in bar, T in K) as follows:

Vapor pressure functions of the pentenes
	T (K)	A.	B.	C.
1-pentene	285.98-303.87	3,91058	1014.294	−43.367
cis -2-pentene	274.74-342.03	3,99984	1069.229	−42.393
trans -2-pentene	274.18-341.36	4.03089	1084.165	−40.158
2-methyl-1-butene	274.30-335.82	3.98652	1047.811	−41.089
2-methyl-2-butene	276.19-343.74	4.04727	1098.619	−39.889
3-methyl-1-butene	273.37-324.29	3.95126	1013,575	−36.32

Extraction

Pentenes are components of coal tar , shale oil , cracked gases and cracked gasoline and can be obtained by fractional distillation . During pyrolysis of rubber , 2-methyl-but-1-ene and 2-methyl-but-2-ene are formed.

Pentenes are formed by dehydration ( elimination of water) from pentanols (so-called amyl alcohols ). In this way, z. B. from fusel oils pentenes (so-called. Fuselölamylen ) win.

use

Pentenes are used for the synthesis of amylphenols , isoprene and pentanols , as well as for polymerization . In addition, amylenes are added as stabilizers, chloroform and dichloromethane , in order to intercept the phosgene formed under the influence of air and light .

Individual evidence

1. ↑ Data sheet 1-pentenes from Sigma-Aldrich , accessed on May 6, 2011 ( PDF ).
2. ↑ Data sheet cis-2-pentenes from Sigma-Aldrich , accessed on May 6, 2011 ( PDF ).
3. ↑ Trans-2-pentenes data sheet from Sigma-Aldrich , accessed on May 6, 2011 ( PDF ).
4. ↑ 2-Methyl-1-butene data sheet from Sigma-Aldrich , accessed on May 6, 2011 ( PDF ).
5. ↑ 2-Methyl-2-butene data sheet from Sigma-Aldrich , accessed on May 6, 2011 ( PDF ).
6. ↑ 3-Methyl-1-butene data sheet from Sigma-Aldrich , accessed on May 6, 2011 ( PDF ).
7. ↑ AF Forziati, DL Camin, FD Rossini: density, refractive index, boiling point, and vapor pressure of eight mono-olefin (1-alkenes), six pentadiene, and two cyclomonoolefin hydrocarbons. In: J. Res. NBS. 45, 1950, pp. 406-410.
8. ↑ ^{a b c} D. W. Scott, G. Waddington: Vapor Pressure of cis-2-pentenes, trans-2-pentenes and 3-methyl-1-butenes. In: J. Am. Chem. Soc. 72, 1950, pp. 4310-4311, ( doi: 10.1021 / ja01165a542 ).
9. ^ ^{A b} D. W. Scott, G. Waddington, JC Smith, HM Huffman: Thermodynamic properties of three isomeric pentenes. In: J. Am. Chem. Soc. 71, 1949, pp. 2767-2773 ( doi: 10.1021 / ja01176a050 ).
10. ↑ Mazin Rida Irani: Stabilized methylene chloride composition and its use for steam degreasing of metals. Patent DE2714836C2 at Patent-de.com, April 2, 1977.

Web links

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