2-Methylbutane Chemical Properties

Melting point:

-160 °C

Boiling point:

30 °C(lit.)

Density 

0.62 g/mL at 25 °C(lit.)

vapor density 

2.6 (vs air)

vapor pressure 

11.17 psi ( 20 °C)

refractive index 

n20/D 1.354(lit.)

Flash point:

−51 °C

storage temp. 

2-8°C

solubility 

0.048g/l

form 

Liquid

pka

>14 (Schwarzenbach et al., 1993)

color 

Clear colorless

Odor

gasoline-like odor

Odor Threshold

1.3ppm

explosive limit

1.3-7.6%(V)

Water Solubility 

Miscible with water, hydrocarbons, oils, alcohol and ether.

λmax

λ: 192 nm Amax: 1.00
λ: 210 nm Amax: 0.30
λ: 220 nm Amax: 0.07
λ: 240-400 nm Amax: 0.01

BRN 

1730723

Henry's Law Constant

(atm?m³/mol): 1.24 at 25 °C (approximate - calculated from water solubility and vapor pressure)

Exposure limits

ACGIH TLV: TWA 600 ppm (adopted).

Dielectric constant

1.8（20℃）

Stability:

Stable. Extremely flammable. Incompatible with strong oxidizing agents. Vapour-air mixtures explosive in certain proportions. Incompatible with rubber, various plastics. The vapour, being heavier than air, may roll over surfaces and collect in low points. Note low flash point.

LogP

3.4 at 20℃

CAS DataBase Reference

78-78-4(CAS DataBase Reference)

NIST Chemistry Reference

Butane, 2-methyl-(78-78-4)

EPA Substance Registry System

2-Methylbutane (78-78-4)

Safety Information

Hazard Codes 

F+,Xn,N

Risk Statements 

12-51/53-65-66-67

Safety Statements 

9-16-29-33-61-62

RIDADR 

UN 1265 3/PG 1

OEB

A

OEL

TWA: 120.0 ppm; 350.0 mg/m3, STEL: 610.0 ppm; 1800.0 mg/m3

WGK Germany 

2

RTECS 

EK4430000

Autoignition Temperature

788 °F

TSCA 

Yes

HazardClass 

3

PackingGroup 

I

HS Code 

29011000

Hazardous Substances Data

78-78-4(Hazardous Substances Data)

MSDS

• Language:English Provider:ACROS
• Language:English Provider:SigmaAldrich
• Language:English Provider:ALFA

2-Methylbutane Usage And Synthesis

Chemical Properties

2-Methylbutane (isopentane), C5H12, is a flammable liquid and exhibits physical properties very similar to those of pentane. It has been detected in urban air.

2-Methylbutane is an alkane that is butane substituted by a methyl group at position 2. It has a higher BP than butane because, although similarly branched, it has a higher MW. A useful analogy for comparing molecules with the same size of longest chain is that of cylindrical-shaped molecules. It has a role as a refrigerant. Biological samples flash frozen for example with a combination of liquid nitrogen and methylbutane can then be used for storage, cryosection, etc.

Physical properties

Clear, colorless, watery, very flammable liquid with a pleasant odor. Evaporates quickly when spilled. An odor threshold concentration of 1.3 ppm_v was reported by Nagata and Takeuchi (1990).

Uses

Isopentane is an organic, branched-chain alkane with five carbon atoms. 2-Methylbutane undergoes catalytic dehydrogenation in the presence of chromia-alumina catalyst to form isoamylenes, which can undergo further dehydrogenation to form isoprene. It may also be used as a solvent in the preparation of trans-Bis(triethylphosphine) (hydroxy carbonyl) (phenyl) platinum(II), a metallacarboxylic acid.

Uses

2-Methylbutane is used as a chemical intermediate. It acts as a blowing agent for polystyrene and gasoline additive. It is used as a solvent of polyethylene and involved in the preparation of polystyrene foam and polyurethane foam. Further, it is used in a closed loop in geothermal power production to operate turbines. In addition to this, it is used to freeze biological samples like tissues in place of dry ice for cryosectioning in histology.

Preparation

2-Methylbutane was synthesized by liquid-phase catalytic isomerization at 95°C using pentane as raw material.

Production Methods

Isopentane is produced by fractional distillation of natural gas liquids and crude oil.

Definition

ChEBI: 2-methylbutane is an alkane that is butane substituted by a methyl group at position 2. It has a role as a refrigerant.

General Description

Watery colorless liquid with a gasoline-like odor. Floats on water. Flammable, irritating vapor is produced. Boiling point is 82°F.

Air & Water Reactions

Highly flammable. Insoluble in water.

Reactivity Profile

2-Methylbutane is a fire and explosion hazard when in contact with oxidizing agents. .

Health Hazard

Inhalation causes irritation of respiratory tract, cough, mild depression, irregular heartbeat. Aspiration causes severe lung irritation, coughing, pulmonary edema; excitement followed by depression. Ingestion causes nausea, vomiting, swelling of abdomen, headache, depression.

Fire Hazard

Behavior in Fire: Highly volatile liquid. Vapors may explode when mixed with air.

Flammability and Explosibility

Extremely flammable

Safety Profile

Mddly toxic and narcotic by inhalation. See also PENTANE. Flammable liquid. A very dangerous fire and explosion hazard when exposed to heat, flame, or oxidzers. Keep away from sparks, heat, or open flame; can react with oxidizing materials. To fight fire, use foam, CO2, dry chemical. When heated to decomposition it emits acrid smoke and irritating fumes.

Source

A constituent in gasoline. Harley et al. (2000) analyzed the headspace vapors of three grades of unleaded gasoline where ethanol was added to replace methyl tert-butyl ether. The gasoline vapor concentrations of 2-methylbutane in the headspace were 24.1 wt % for regular grade, 24.8 wt % for mid-grade, and 26.0 wt % for premium grade.
Schauer et al. (2001) measured organic compound emission rates for volatile organic compounds, gas-phase semi-volatile organic compounds, and particle-phase organic compounds from the residential (fireplace) combustion of pine, oak, and eucalyptus. The gas-phase emission rate of 2-methylbutane was 5.6 mg/kg of pine burned. Emission rates of 2-methylbutane were not measured during the combustion of oak and eucalyptus.
California Phase II reformulated gasoline contained 2-methylbutane at a concentration of 79.2g/kg. Gas-phase tailpipe emission rates from gasoline-powered automobiles with and without catalytic converters were 3.69 and 148 μg/km, respectively (Schauer et al., 2002).

Environmental Fate

Photolytic. When synthetic air containing gaseous nitrous acid and 2-methylbutane was exposed to artificial sunlight (λ = 300–450 nm), acetone, acetaldehyde, methyl nitrate, peroxy-acetal nitrate, propyl nitrate, and pentyl nitrate were formed (Cox et al., 1980).
Based upon a photooxidation rate constant of 3.90 x 10^-12 cm³/molecule?sec with OH radicals in summer daylight, the atmospheric lifetime is 36 h (Altshuller, 1991). At atmospheric pressure and 300 K, Darnall et al. (1978) reported a rate constant of 3.78 x 10^-12 cm³/molecule?sec for the same reaction.
Cox et al. (1980) reported a rate constant of 5.0 x 10^-11 cm³/molecule?sec for the reaction of gaseous 2-methylbutane with OH radicals based on a value of 8 x 10^-12 cm³/molecule?sec for the reaction of ethylene with OH radicals.
Chemical/Physical. Complete combustion in air produces carbon dioxide and water vapor.
2-Methylbutane will not hydrolyze because it does not contain a hydrolyzable functional group.

Purification Methods

Stir isopentane for several hours in the cold with conc H2SO4 (to remove olefinic impurities), then wash it with H2O, aqueous Na2CO3 and H2O again. Dry it with MgSO4 and fractionally distil it using a Todd column packed with glass helices. Material transparent down to 180nm is obtained by distilling from sodium wire, and passing through a column of silica gel which had previously been dried in place at 350o for 12hours before use. [Potts J Phys Chem 20 809 1952, Beilstein 1 IV 320.]

2-Methylbutane(78-78-4)Related Product Information

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