2,3-Dimethylpentane is an

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon- hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. Th ...

carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon makes ...

and

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic ...

with formula , more precisely ––––: a molecule of

pentane Pentane is an organic compound with the formula C5H12—that is, an alkane with five carbon atoms. The term may refer to any of three structural isomers, or to a mixture of them: in the IUPAC nomenclature, however, pentane means exclusively the ' ...

with

methyl group In organic chemistry, a methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms, having chemical formula . In formulas, the group is often abbreviated as Me. This hydrocarbon group occurs in ma ...

s – replacing hydrogen atoms on carbon atoms 2 and 3. It is an

alkane In organic chemistry Organic chemistry is a subdiscipline within chemistry involving the science, scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms tha ...

("paraffin" in older nomenclature), a fully saturated

hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or ...

; specifically, one of the isomers of

heptane Heptane or ''n''-heptane is the straight-chain alkane with the chemical formula H3C(CH2)5CH3 or C7H16. When used as a test fuel component in anti-knock test engines, a 100% heptane fuel is the zero point of the octane rating scale (the 100 poi ...

. Like typical alkanes, it is a colorless flammable compound; under common ambient conditions, it is a mobile liquid, less dense than water.Alfonso S. Pensado, María J. P. Comuñas, Luis Lugo, and Josefa Fernández (2005): "Experimental Dynamic Viscosities of 2,3-Dimethylpentane up to 60 MPa and from (303.15 to 353.15) K Using a Rolling-Ball Viscometer". ''Journal of Chemical & Engineering Data'', volume 50, issue 3, pages 849–855. 2,3-Dimethylpentane is notable for being one of the two simplest alkanes with optical (enantiomeric) isomerism. The

optical center In Gaussian optics, the cardinal points consist of three pairs of Point (geometry), points located on the optical axis of a Rotational symmetry, rotationally symmetric, focal, optical system. These are the ''Focus (optics), focal points'', the pr ...

is the middle carbon of the pentane backbone, which is connected to one hydrogen atom, one methyl group, one

ethyl group In organic chemistry, an ethyl group (abbr. Et) is an alkyl substituent with the formula , derived from ethane (). ''Ethyl'' is used in the International Union of Pure and Applied Chemistry's nomenclature of organic chemistry for a saturat ...

–, and one

isopropyl group In organic chemistry, propyl is a three-carbon alkyl substituent with chemical formula for the linear form. This substituent form is obtained by removing one hydrogen atom attached to the terminal carbon of propane. A propyl substituent is often ...

–. The two enantiomers are denoted (3''R'')-2,3-dimethylpentane and (3''S'')-2,3-dimethylpentane. (The other simplest chiral alkane is its

structural isomer In chemistry, a structural isomer (or constitutional isomer in the IUPAC nomenclature) of a compound is another compound whose molecule has the same number of atoms of each element, but with logically distinct bonds between them. The term met ...

3-methylhexane.)

Properties

Most properties listed in the literature refer to the racemic compound (an equimolar mixture of the two

optical isomers In chemistry, a molecule or ion is called chiral () if it cannot be superposed on its mirror image by any combination of rotations, translations, and some conformational changes. This geometric property is called chirality (). The terms ar ...

). The boiling point of 89.7 °C is 0.3 °C higher than the value of 89.4 °C predicted by Wiener's formula, based on the structure of the molecule and the boiling point of ''n''-heptane.Pentane, 2,3-dimethyl-
NIST Chemistry WebBook, SRD 69. Accessed on 2018-11-06.Harry Wiener (1947): "Structural Determination of Paraffin Boiling Points". ''Journal of the American Chemical Society'', volume 69, issue 1, pages 17–20. The speed of sound at 3

MHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that one h ...

is 1149.5 m/s at 20 °C and 889.5 m/s at 80 °C.F. Plantier and J. L. Daridon (2005): "Speed of Sound of 2-Methylpentane, 2,3-Dimethylpentane, and 2,2,4-Trimethylpentane from (293.15 to 373.15) K and up to 150 MPa". ''Journal of Chemical & Engineering Data'', volume 50, issue 6, pages 2077–2081. . Note: density values 0.6943 g/mL at 20 °C and 0.6377 at 80°C differ significantly from those of Pensado et al. Also gives data at 100 kPA up to 100 °C which is above the boiling point.Egbert B. Freyer, J. C. Hubbard, and Donald H. Andrews (1929): "Sonic studies of the physical properties of liquids. I. The sonic interferometer. The velocity of sound in some organic liquids and their compressibilities". ''Journal of the American Chemical Society'', volume 51, issue 3, pages 759–770. Note: gives speed of ~400 Hz sound as 1148.5 at 20 °C and 1039 m/s at 45 °C, and density 0.6942 g/mL at 20 °C.J. L. E. Chevalier, P. J. Petrino, and Y. H. Gaston-Bonhomme (1990): "Viscosity and density of some aliphatic, cyclic, and aromatic hydrocarbons binary liquid mixtures". ''Journal of Chemical & Engineering Data'', volume 35, issue 2, pages 206–212. . Gives kinematic viscosity 0.5513 m²/s and density 0.69026 g/mL at 25 °C. The racemic mixture has a glass transition temperature of about 123 K (−150 °C), but reportedly it does not crystallize—a fact that has been claimed to be a characteristic of high-purity optically active alkanes.H. L. Finke, J. F. Messerly, D. R. Douslin (1976): "Low-temperature thermal quantities for five alkyl-substituted pentanes". ''The Journal of Chemical Thermodynamics'', volume 8, issue 10, pages 965-983. John M. Smith, John M. Simmie, Henry J. Curran (2005): "Autoignition of heptanes; experiments and modeling". ''International Journal of Chemical Kinetics'', volume 37, issue 12, pages 728-736.

Preparation

2,3-Dimethylpentane is practically absent in the synthetic fuel produced from hydrogen and

carbon monoxide Carbon monoxide ( chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the si ...

by the

Fischer–Tropsch process The Fischer–Tropsch process is a collection of chemical reactions that converts a mixture of carbon monoxide and hydrogen, known as syngas, into liquid hydrocarbons. These reactions occur in the presence of metal catalysts, typically at temperatu ...

.R. A. Friedel, and R. B. Anderson (1950): "Composition of Synthetic Liquid Fuels. I. Product Distribution and Analysis of C5—C8 Paraffin Isomers from Cobalt Catalyst". ''Journal of the American Chemical Society'', volume 72, issue 3, pages 1212–1215. The pure compound can be prepared by reacting the Grignard reagent ''sec''-butyl magnesium bromide – with

acetone Acetone (2-propanone or dimethyl ketone), is an organic compound with the formula . It is the simplest and smallest ketone (). It is a colorless, highly volatile and flammable liquid with a characteristic pungent odour. Acetone is miscible wi ...

to form 2,3-dimethyl-2-pentanol, then dehydrating this

alcohol Alcohol most commonly refers to: * Alcohol (chemistry), an organic compound in which a hydroxyl group is bound to a carbon atom * Alcohol (drug), an intoxicant found in alcoholic drinks Alcohol may also refer to: Chemicals * Ethanol, one of sev ...

to form 2,3-dimethyl-2-pentene, and hydrogenating this product.Graham Edgar, George Calingaert, and R. E. Marker (1929): The preparation and properties of the isomeric heptanes. Part I. Preparation". ''Journal of the American Chemical Society'', volume 51, issue 5, pages 1483–1491. . Density 0.6952, refractive index 1.39201 at 20 °C. The isomer is present at about 2.4% by weight in the hydrocarbon mixture obtained by the condensation of methanol at 200 °C with a

zinc iodide Zinc iodide is the inorganic compound with the formula ZnI2. It exists both in anhydrous form and as a dihydrate. Both are white and readily absorb water from the atmosphere. It has no major application. Preparation It can be prepared by the dire ...

catalyst Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

(the main component of the mixture being the isomer

2,2,3-trimethylbutane Triptane, or 2,2,3-trimethylbutane, is an organic chemical compound with the molecular formula C7 H16 or (H3C-)3C-C(-CH3)2H. It is therefore an alkane, specifically the most compact and heavily branched of the heptane isomers, the only one with ...

, obtained at almost 50% yield).Leo Kim, Milton M. Wald, Stanley G. Brandenberger (1978): "One-step catalytic synthesis of 2,2,3-trimethylbutane from methanol." ''Journal of Organic Chemistry'', volume 43, issue 17, pages 3432-3433.

References

{{DEFAULTSORT:Dimethylpentane, 2, 3- Alkanes

Properties

Preparation

See also

References