Profile
Settings
Refer your friends
Sign out
Alkanes are organic compounds composed of carbon and hydrogen atoms that are single-bonded. Alkanes have the formula CnH2n+2 and are split into three groups: chain alkanes, cycloalkanes, and branched alkanes.
Alkanes are saturated hydrocarbons
Alkanes are a class of chemicals that possess single covalent connections between carbon and hydrogen atoms. Saturated hydrocarbons are what they’re called. This category of chemicals is constituted of solitary covalent connections between carbon and hydrogen atoms. A homologous series with the chemical formula CnH2n+2 is also included.
Alkanes are the most basic hydrocarbon family. They are made up entirely of carbon and hydrogen. Each carbon atom has four bonds, whereas each hydrogen atom has one. Chemists prefer line-angle formulae over condensed structural formulas because they are easier and faster to draft. Alkane structural formulae can also be expressed in a condensed form.
Chemistry of Alkane Formulas
Organic compound formulas provide information at various levels of complexity. The number of each kind of atom in a molecule of a substance is determined using molecular formulae, such as the one for octane. The molecular formula C8H18 can refer to many varieties of alkanes, each with its own set of chemical, physical, and toxicological characteristics. The structural formulae for these various compounds reveal the sequence in which the atoms in a molecule are organized. Structural isomers are compounds of the same molecular formula but having variation in structural formulae.
Alkanes may be used to make almost any organic compound. Also, many critical segments of organic compounds have one or more alkane groups bound as substituents onto the underlying organic molecule without a hydrogen atom. As a result of these consequences, alkanes are used in the names of numerous organic substances.
Some Physical properties of Alkane
Alkanes and Their Boiling Point
As the molecular size and thus the surface area of the molecule increases, the intermolecular Van Der Waals forces rise as well.
The boiling point of alkanes rises with increasing molecular weight, in case of straight-chain alkanes boiling at a greater temperature than their structural isomers.
Alkanes and Their Melting point
The melting point of alkanes follows the same outline as their boiling point: it rises as the molecular weight rises.
This is due to the detail that higher alkanes are solids, making intermolecular forces of attraction difficult to overcome.
Even-numbered alkanes have a higher melting point trend than odd-numbered alkanes, due to the fact that even-numbered alkanes pack well in the solid phase, generating a well-organized structure that is difficult to break.
Density
The size of the hydrophilic head group and its interactions with counterions in the subphase and other head groups inside the plane define the mean molecular area of an amphiphile. The alkyl chains pack to optimise hoth van der Waals contacts and alkane density once these interactions are at an energy minimum. A minimal cross-sectional area per molecule may be calculated by extrapolating the steepest region of the curve before the collapse at zero pressure. One of the first approaches for determining the size of a molecule was to utilise this method.
Solubility of Alkanes
Alkanes (both alkanes and cycloalkanes) are water insoluble but soluble in organic solvents. Liquid alkanes, on the other hand, are effective solvents for a wide range of non-ionic organic molecules.
Solubility in inorganic solvent (water)
The following must happen when a molecular compound dissolves in water:
Within the material, disrupt the intermolecular forces. These are the Van der Waals dispersion forces in the case of alkanes.
In order for the material to fit between the water molecules, the intermolecular forces in the water must be broken. Hydrogen bonds are the fundamental intermolecular attractions in water.
Breaking either of these attractions needs energy, albeit the amount of energy required to break the Van der Waals dispersion forces in methane is small compared to the hydrogen bonds in water. To simplify things, a material will dissolve if enough energy is released when new bonds between the substance and the water are formed to compensate for the energy expended in breaking the original attractions. Van der Waals forces are the sole new attractions between the alkane and water molecules. The alkane does not dissolve because these forces do not release enough energy to compensate for the energy required to break the hydrogen bonds in water.
Because entropic effects are also relevant when objects dissolve, the energy-only account of solvation is an oversimplification.
Solubility in organic solvents
The principal forces of attraction between the solvent molecules in most organic solvents are Van der Waals – either dispersion forces or dipole-dipole attractions. When an alkane dissolves in an organic solvent, the Van der Waals forces are disrupted and new Van der Waals forces are formed. There is no barrier to solubility since the two processes almost balance each other out energetically.
Conclusion
This article consists of the physical properties of alkanes which are mainly its boiling point, melting point, solubility and density. Alkanes are saturated hydrocarbons having capability to form long chain bonds of carbon and hydrogen. There is a specific trend among their boiling point, melting point, density and solubility with the increase in the carbon number in the parent chain.
