Isopentane

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Structural formula
Structural formula of isopentane
General
Surname Isopentane
other names
Molecular formula C 5 H 12
Brief description

colorless liquid with a gasoline-like odor 

External identifiers / databases
CAS number 78-78-4
EC number 201-142-8
ECHA InfoCard 100.001.039
PubChem 6556
Wikidata Q422703
properties
Molar mass 72.15 g mol −1
Physical state

liquid

density

0.62 g cm −3

Melting point

−160 ° C

boiling point

28 ° C

Vapor pressure
  • 761 h Pa (20 ° C)
  • 1080 hPa (30 ° C)
  • 2.042 bar (50 ° C)
solubility
  • practically insoluble in water (0.05 g l −1 at 20 ° C)
  • soluble in ethanol
Refractive index

1.35373

safety instructions
GHS hazard labeling from  Regulation (EC) No. 1272/2008 (CLP) , expanded if necessary
02 - Highly / extremely flammable 08 - Dangerous to health 07 - Warning 09 - Dangerous for the environment

danger

H and P phrases H: 224-304-336-411
EUH: 066
P: 210-261-273-301 + 310-331
MAK

1000 ml m −3 or 3000 mg m −3

As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . Refractive index: Na-D line , 20 ° C

Isopentane , systematically 2-methylbutane or just methylbutane is an organic chemical compound . It systematically belongs to the alkanes . It is one of three structural isomers of pentanes ( n -pentane, isopentane, neopentane ). Accordingly, isopentane has five carbon atoms and has the empirical formula C 5 H 12 . Isopentane is an extremely flammable liquid that boils even at a slightly elevated room temperature.

Extraction and presentation

It is mainly represented by the catalytic isomerization of n -pentane.

properties

Physical Properties

Isopentane is a colorless, volatile liquid that boils at 28 ° C under normal pressure . According to Antoine, the vapor pressure function results from log 10 (P) = A− (B / (T + C)) (P in kPa, T in K) with A = 3.90935, B = 1018.516 and C = −40.081 in the temperature range from 190.3 K to 300.9 K.

Important thermodynamic quantities are given in the following table:

Compilation of the most important thermodynamic properties
property Type Value [unit] Remarks
Standard enthalpy of formation Δ f H 0 liquid
Δ f H 0 gas
−178.2 kJ mol −1
−153.7 kJ mol −1
as a liquid
as a gas
Enthalpy of combustion Δ c H 0 liquid −3504.4 kJ mol −1 as a liquid
Heat capacity c p 164.5 J mol −1 K −1 (25 ° C)
2.27 J g −1 K −1 (25 ° C)
as a liquid
Critical temperature T c 460.4 K
Critical pressure p c 33.8 bar
Critical volume V c 0.306 l mol −1
Critical density ρ c 3.27 mol·l −1
Enthalpy of fusion Δ f H 5.13 kJ mol −1 at the melting point
Enthalpy of evaporation Δ V H 24.69 kJ mol −1 at normal pressure boiling point

The temperature dependence of the evaporation enthalpy can be calculated according to the equation Δ V H 0 = A e (−βT r ) (1 − T r ) βV H 0 in kJ / mol, T r = (T / T c ) reduced temperature ) with A = 39.02 kJ / mol, β = 0.267 and T c = 460.4 K in the temperature range between 279 K and 301 K.

Safety-related parameters

Isopentane forms highly flammable vapor-air mixtures. The compound has a flash point at −57 ° C. The explosion range is between 1.3% by volume (38 g / m 3 ) as the lower explosion limit (LEL) and 7.6% by volume (230 g / m 3 ) as the upper explosion limit (UEL). With a minimum ignition energy of 0.21 mJ, vapor-air mixtures are extremely ignitable. The maximum explosion pressure is 9.1 bar. The limit gap width was determined to be 0.98 mm. This results in an assignment to explosion group IIA. The ignition temperature is 420 ° C. The substance therefore falls into temperature class T2.

use

Isopentane is used as a solvent for fats and oils as well as for the production of isoprene and insecticides . It can also be used as a working medium in the Organic Rankine Cycle , for example in the Landau geothermal power plant. In the histology frozen isopentane is for quick freezing of tissue samples used.

Web links

Commons : Isopentane  - Collection of images, videos, and audio files

Individual evidence

  1. a b c d e f g h i j k l m n o p q r s Entry on isopentane in the GESTIS substance database of the IFA , accessed on January 10, 2017(JavaScript required) .
  2. Data isopentane (PDF) at Merck , accessed on 25 September 2006 .
  3. CRC Handbook of Tables for Organic Compound Identification . 3. Edition. 1984, ISBN 0-8493-0303-6 .
  4. Entry on 2-methylbutane in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on February 1, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .
  5. a b H. Breuer: dtv-Atlas zur Chemie. Volume 2, February 1997.
  6. ^ DR Stull: Vapor Pressure of Pure Substances - Organic Compounds. In: Ind. Eng. Chem. 39, 1947, pp. 517-540. doi: 10.1021 / ie50448a022
  7. a b c W. D. Good: The enthalpies of combustion and formation of the isomeric pentanes. In: J. Chem. Thermodyn. 2, 1970, pp. 237-244. doi: 10.1016 / 0021-9614 (70) 90088-1 .
  8. ^ I. Czarnota: Heat capacity of 2-methylbutane at high pressures. In: J. Chem. Thermodyn. 20, 1988, pp. 457-462. doi: 10.1016 / 0021-9614 (88) 90183-8 .
  9. a b c d T. E. Daubert: Vapor-Liquid Critical Properties of Elements and Compounds. 5. Branched Alkanes and Cycloalkanes. In: J. Chem. Eng. Data . 41, 1996, pp. 365-372. doi: 10.1021 / je9501548 .
  10. Eugene S. Domalski, Elizabeth D. Hearing: Heat Capacities and Entropies of Organic Compounds in the Condensed phase. Volume III. In: J. Phys. Chem. Ref. Data. 25, 1, 1996. doi: 10.1063 / 1.555985 .
  11. ^ A b V. Majer, V. Svoboda: Enthalpies of Vaporization of Organic Compounds: A Critical Review and Data Compilation. Blackwell Scientific Publications, Oxford 1985, p. 300.
  12. a b c d E. Brandes, W. Möller: Safety-related parameters. Volume 1: Flammable Liquids and Gases. Wirtschaftsverlag NW - Verlag für neue Wissenschaft, Bremerhaven 2003.
  13. BG RCI-Merkblatt T 033 Avoidance of ignition hazards due to electrostatic charges. Jedermann-Verlag, 2009, ISBN 978-3-86825-103-6 .
  14. John D. Bancroft, Marilyn Gamble: Theory and Practice of Histological Techniques. Elsevier Health Sciences, 2008, ISBN 978-0-443-10279-0 , p. 99. ( limited preview in Google book search).
  15. Michael Arnold: Histochemistry. Springer-Verlag, 2013, ISBN 978-3-642-49933-3 , p. 92. ( limited preview in Google book search).