2-метилбутан

Химические свойства

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.

Физические свойства

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).

Использование

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.

Методы производства

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

Подготовка

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

Определение

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

Общее описание

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

Реакции воздуха и воды

Highly flammable. Insoluble in water.

Профиль реактивности

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

Угроза здоровью

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.

Пожароопасность

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

Профиль безопасности

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.

Экологическая судьба

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.

Методы очистки

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.]