What are the alkanes? Which are the various properties of Alkanes?

Alkanes are the simplest and the least reactive hydrocarbon species containing only carbons and hydrogen. They are commercially very important, for being the principal constituent of gasoline and lubricating oils are extensively employed in organic chemistry.

In an alkane, each carbon atom is sp3 hybridized with sigma bonds (either C-C or C-H), and each H-atom is joined to one of the carbon atoms ( in a C-H bond). The longest series of linked carbon atom in a molecule is known as its carbon skeleton/ carbon backbone. The no. of carbon atom. The no.of carbon atoms may be considered as the size of alkane. 

Methane:

Methane (one carbon bonded to four hydrogens) is the simplest organic molecule.

Methane

The bonds point to the four corners of the tetrahedron, forming a 108.70-degree bond angle. The carbon atom and the hydrogen atoms within alkanes are connected by single covalent bonds. The number of carbon atoms within an alkane is the main determiner of an alkane. 

Alkanes are a group of saturated hydrocarbons. The carbon atoms and the hydrogen atoms within alkanes are connected by single covalent bonds.

Hazards: Methane is flammable,dangerous to inhale and explosive, because it is colorless, odorless gas, special caution must be taken around methane.

Alkane also pose a threat to the environment. Branched alkanes have a longer biodegradability than unbranched alkanes. However methane is ranked as the most dangerous greenhouse gas. Although the amount of methane in the atmosphere is low, it dose pose a threat to the environment. 

Examples of the functions of some alkanes are identified below. 

1. The first four alkanes are used for heating and cooking or electricity. for e.g. methane is used within natural gas.

2. Propane and butane are found within liquid petroleum gas. for e.g. propane gas is used as fuel for cars. Butane is the gas that is used in cigarette lighters.

3. Alkanes with five to eight carbons, pentane to octane, are volatile. Therefore, they are used in internal combustion engines. They are also commonly used as solvents for non-polar substances. 

4. Alkanes with nine to sixteen carbons, nonane to hexadecane, are used in diesel and aviation fuels.

Alkanes can be prepared from alkene and alkyne through the process of hydrogenation. In this process, dihydrogen gas is added to alkynes and alkenes in the present catalyst. This catalyst which is finally divided is like nickel, palladium, or platinum to form alkanes.Alkanes are known as paraffin or collectively as the paraffin series. These terms are also used for alkanes whose carbon atoms form a single, unbranched chain. Branched-chain alkanes are called isoparaffins.

Chemical properties:

The pka value of all alkanes are above 50, so they are practically inert to acid and bases. This inertness is the source of the paraffin.Alkanes are saturated hydrocarbons this means that their carbon atoms are joined to each other by single bonds. this makes then relatively unreactive, apart from their reaction with oxygen in the air- which we call burning or combustion.

Physical properties:

Alkanes are colourless. Alkanes are less dense than water. Alkanes are non-polar molecules so they are more soluble in non-polar solvents than they are in polar solvents.The melting point of the shorter chain alkanes is low, but melting and biolings of of alkane increase as the no. of carbon atoms in the carbo chain increases. 

Spectroscopic properties:

Effectively all organic compounds contain carbon-carbon, and carbon-hydrogen bonds, and so show some of the features of alkane in their spectra. Alkanes are notable for having no other groups, and therefore for the absence of other characteristic spectroscopic features of a functional group like -OH, -CHO, -COOH etc. 

Infrared spectroscopy:

The C-H stretching mode gives a strong absorption between 2850 and 2960 c/m, while the carbon-carbon stretching mode absorbs between 800 and 1300 c/m. 

NMR spectroscopy:

The proton resonance of alkanes are usually found at δH = 0.5–1.5. The carbon - 13 resonances depend on the no.of H-atoms attached to the carbon. 

Mass spectroscopy:

Alkanes have a high ionization energy, and the molecular ion is usually weak. The fragmentation pattern can be difficult to interpret, but in the case of Branched-chain alkane the carbon chain is preferentially cleaved at a tertiary or quaternary quaternary carbons due to the relative stability of resulting free radical. The fragment resulting from the loss of a single methyl group (M-15) is often absent, and other fragments are often spaced by intervals of fourteen mass units, corresponding to the sequential loss of -CH2 groups.