2-Methylhexane
Encyclopedia
2-Methylhexane is an isomer
of heptane
. It is structurally a hexane
molecule with a methyl group
attached to its second carbon atom. It exists in most commercially available heptane merchandises as an impurity
but is usually not considered as impurity in terms of reactions since it has very similar physical
and chemical properties
when compared to n-heptane (straight-chained heptane).
Being an alkane, 2-methylhexane is insoluble in water
, but is soluble in many organic solvents, such as alcohol
s and ether
. However, 2-methylhexane is more commonly considered as a solvent
itself. Therefore, even though it is present in many commercially available heptane products, it is not considered as a destructive impurity, as heptane is usually used as a solvent. Nevertheless, by concise processes of distillation
and refining
, it is possible to separate 2-methylhexane from n-heptane.
Within a group of isomers, those with more branches
tend to ignite more easily and combust
more completely. Therefore, 2-methylhexane has a lower autoignition temperature
and flash point
when compared to heptane. Theoretically 2-methylhexane also burns with a less sooty flame, emitting higher-frequency radiation; however, as heptane and 2-methylhexane differ by only one carbon atom
, in terms of branching, both burn with a bright yellow flame when ignited.
Compared to n-heptane, 2-methylhexane also has lower melting
and boiling point
s. A lower density of liquid is found in 2-Methylhexane than heptane.
On the NFPA 704
scale, 2-methylhexane is listed as a reactivity level-0 chemical, along with various other alkane
s. In fact, most alkanes are unreactive except in extreme conditions, such as combustion or strong sunlight
. At the presence of oxygen
and flame
, 2-methylhexane, like heptane, combusts mostly completely into water
and carbon dioxide
. With UV-light
and mixed with halogen
s in solvents, usually bromine
in 1,1,1-trichloroethane
, a substitution reaction
occurs.
Isomer
In chemistry, isomers are compounds with the same molecular formula but different structural formulas. Isomers do not necessarily share similar properties, unless they also have the same functional groups. There are many different classes of isomers, like stereoisomers, enantiomers, geometrical...
of heptane
Heptane
n-Heptane is the straight-chain alkane with the chemical formula H3C5CH3 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...
. It is structurally a hexane
Hexane
Hexane is a hydrocarbon with the chemical formula C6H14; that is, an alkane with six carbon atoms.The term may refer to any of four other structural isomers with that formula, or to a mixture of them. In the IUPAC nomenclature, however, hexane is the unbranched isomer ; the other four structures...
molecule with a methyl group
Methyl group
Methyl group is a functional group derived from methane, containing one carbon atom bonded to three hydrogen atoms —CH3. The group is often abbreviated Me. Such hydrocarbon groups occur in many organic compounds. The methyl group can be found in three forms: anion, cation and radical. The anion...
attached to its second carbon atom. It exists in most commercially available heptane merchandises as an impurity
Impurity
Impurities are substances inside a confined amount of liquid, gas, or solid, which differ from the chemical composition of the material or compound.Impurities are either naturally occurring or added during synthesis of a chemical or commercial product...
but is usually not considered as impurity in terms of reactions since it has very similar physical
Physical property
A physical property is any property that is measurable whose value describes a physical system's state. The changes in the physical properties of a system can be used to describe its transformations ....
and chemical properties
Chemical property
A chemical property is any of a material's properties that becomes evident during a chemical reaction; that is, any quality that can be established only by changing a substance's chemical identity...
when compared to n-heptane (straight-chained heptane).
Being an alkane, 2-methylhexane is insoluble in water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
, but is soluble in many organic solvents, such as alcohol
Alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....
s and ether
Ether
Ethers are a class of organic compounds that contain an ether group — an oxygen atom connected to two alkyl or aryl groups — of general formula R–O–R'. A typical example is the solvent and anesthetic diethyl ether, commonly referred to simply as "ether"...
. However, 2-methylhexane is more commonly considered as a solvent
Solvent
A solvent is a liquid, solid, or gas that dissolves another solid, liquid, or gaseous solute, resulting in a solution that is soluble in a certain volume of solvent at a specified temperature...
itself. Therefore, even though it is present in many commercially available heptane products, it is not considered as a destructive impurity, as heptane is usually used as a solvent. Nevertheless, by concise processes of distillation
Distillation
Distillation is a method of separating mixtures based on differences in volatilities of components in a boiling liquid mixture. Distillation is a unit operation, or a physical separation process, and not a chemical reaction....
and refining
Refining
Refining is the process of purification of a substance or a form. The term is usually used of a natural resource that is almost in a usable form, but which is more useful in its pure form. For instance, most types of natural petroleum will burn straight from the ground, but it will burn poorly...
, it is possible to separate 2-methylhexane from n-heptane.
Within a group of isomers, those with more branches
Branching (chemistry)
In polymer chemistry, branching occurs by the replacement of a substituent, e.g., a hydrogen atom, on a monomer subunit, by another covalently bonded chain of that polymer; or, in the case of a graft copolymer, by a chain of another type...
tend to ignite more easily and combust
Combustion
Combustion or burning is the sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species. The release of heat can result in the production of light in the form of either glowing or a flame...
more completely. Therefore, 2-methylhexane has a lower autoignition temperature
Autoignition temperature
The autoignition temperature or kindling point of a substance is the lowest temperature at which it will spontaneously ignite in a normal atmosphere without an external source of ignition, such as a flame or spark. This temperature is required to supply the activation energy needed for combustion...
and flash point
Flash point
The flash point of a volatile material is the lowest temperature at which it can vaporize to form an ignitable mixture in air. Measuring a flash point requires an ignition source...
when compared to heptane. Theoretically 2-methylhexane also burns with a less sooty flame, emitting higher-frequency radiation; however, as heptane and 2-methylhexane differ by only one carbon atom
Atom
The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons...
, in terms of branching, both burn with a bright yellow flame when ignited.
Compared to n-heptane, 2-methylhexane also has lower melting
Melting point
The melting point of a solid is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure and is usually specified at standard atmospheric pressure...
and boiling point
Boiling point
The boiling point of an element or a substance is the temperature at which the vapor pressure of the liquid equals the environmental pressure surrounding the liquid....
s. A lower density of liquid is found in 2-Methylhexane than heptane.
On the NFPA 704
NFPA 704
NFPA 704 is a standard maintained by the U.S.-based National Fire Protection Association. It defines the colloquial "fire diamond" used by emergency personnel to quickly and easily identify the risks posed by nearby hazardous materials...
scale, 2-methylhexane is listed as a reactivity level-0 chemical, along with various other alkane
Alkane
Alkanes are chemical compounds that consist only of hydrogen and carbon atoms and are bonded exclusively by single bonds without any cycles...
s. In fact, most alkanes are unreactive except in extreme conditions, such as combustion or strong sunlight
Sunlight
Sunlight, in the broad sense, is the total frequency spectrum of electromagnetic radiation given off by the Sun. On Earth, sunlight is filtered through the Earth's atmosphere, and solar radiation is obvious as daylight when the Sun is above the horizon.When the direct solar radiation is not blocked...
. At the presence of oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
and flame
Flame
A flame is the visible , gaseous part of a fire. It is caused by a highly exothermic reaction taking place in a thin zone...
, 2-methylhexane, like heptane, combusts mostly completely into water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
and carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
. With UV-light
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
and mixed with halogen
Halogen
The halogens or halogen elements are a series of nonmetal elements from Group 17 IUPAC Style of the periodic table, comprising fluorine , chlorine , bromine , iodine , and astatine...
s in solvents, usually bromine
Bromine
Bromine ") is a chemical element with the symbol Br, an atomic number of 35, and an atomic mass of 79.904. It is in the halogen element group. The element was isolated independently by two chemists, Carl Jacob Löwig and Antoine Jerome Balard, in 1825–1826...
in 1,1,1-trichloroethane
1,1,1-Trichloroethane
The organic compound 1,1,1-trichloroethane, also known as methyl chloroform, is a chloroalkane. This colourless, sweet-smelling liquid was once produced industrially in large quantities for use as a solvent...
, a substitution reaction
Substitution reaction
In a substitution reaction, a functional group in a particular chemical compound is replaced by another group. In organic chemistry, the electrophilic and nucleophilic substitution reactions are of prime importance...
occurs.