Profile
Settings
Refer your friends
Sign out
Alcohol can be considered to be derivatives of water in some cases (H2O; also written as HOH).
The R–O–H link is bent in the same way that the H–O–H bond is curved in water, and alcohol molecules are polar. When a hydrogen atom from an alkane is replaced with an OH group, the molecules are able to associate with one another through hydrogen bonding.
In part, this is due to the presence of hydroxyl groups in water molecules, which may make hydrogen bonds with other water molecules as well as with alcohol molecules. In turn, alcohol molecules can form hydrogen bonds with other alcohol molecules as well as with other water molecules. The formation of hydrogen bonds between alcohols and water results in the alcohols’ relative solubility in water.
At room temperature, the vast majority of ordinary alcohols are clear, colourless liquids. Free-flowing liquids with fruity aromas, methylated spirits, ethanol, and isopropylated spirits are all types of alcohol. When it comes to higher alcohols, those with 4 to 10 carbon atoms have a thick or oily consistency, and their aromas are more strongly fruity. Even at normal temperature, some of the more highly branched alcohols and many of the alcohols containing more than 12 carbon atoms can be found to be solids.
Physical Properties of Alcohol
Alcohols have substantially higher boiling points than alkanes, which makes them more suitable for use as solvents. The hydroxyl groups found in alcohol molecules are responsible for the formation of hydrogen bonds between the molecules of alcohol.
In order to overcome these strong intermolecular interactions, the melting and boiling temperatures of alcohols are higher than those of alkanes with a corresponding chain length because more energy is required.
Boiling points of alcohols will rise even further as the number of hydroxyl groups in the alcohols increases. When alcohol contains two hydroxyl groups, the alcohol is referred to as a diol. A triol is a molecule that has three hydroxyl groups.
The substantial increase in the boiling point of alcohol that occurs as the number of hydroxyl groups in the alcohol increases is due to a greater degree of hydrogen bonding occurring between the molecules.
The Boiling Point of Alcohol
Compared to other hydrocarbons with equal molecular weights, alcohols have greater boiling points on average than these other hydrocarbons. Intermolecular hydrogen bonding exists between the hydroxyl groups of alcohol molecules, and this is what causes this phenomenon to occur. According to general chemistry, the boiling point of alcohol rises with an increase in the number of carbon atoms present in the aliphatic carbon chain. However, the boiling point of aliphatic carbon chains lowers as the number of branches increases, and the Van der Waals forces diminish as the surface area of the carbon chain decreases as well. As a result, primary alcohols have a greater boiling point than secondary alcohols.
Factors Affecting Boiling Point
Pressure
When the pressure is less than one bar, the boiling point of a liquid is lower than the typical boiling point. As soon as the pressure equals one bar, the boiling point of a liquid is equal to its usual boiling point. When the pressure is greater than 1 bar, the boiling point of a liquid is higher than the typical boiling point.
Types of Molecules
The boiling point of a liquid is determined by the types of molecules that make up the liquid. If the intermolecular forces between the molecules are equal to:
When a liquid’s boiling point is relatively high, it indicates that the liquid is relatively powerful.
When the boiling point of a liquid is low, it indicates that the liquid has a weak boiling point.
Solubility of Alcohols
Alcohols are only weakly to moderately soluble in water, depending on the concentration. The hydroxyl group of alcohols, which is typically referred to as a hydrophilic (water-loving) component, is responsible for the tendency of alcohols to form hydrogen bonds with water. The solubility of alcohol in water is increased as a result of this characteristic.
Alcohols with a short hydrocarbon chain have a tendency to be particularly soluble in water. As the length of the hydrocarbon chain lengthens, the solubility of alcohol in water diminishes in a progressive manner.
The primary reason for the decrease in solubility as the length of the hydrocarbon chain increases is that a greater amount of energy is required to break the hydrogen bonds that exist between the alcohol molecules. The length of the hydrocarbon chain is the primary reason for the decrease insolubility. Normally, as the mass and size of the molecules increase, the molecules remain tightly packed together in close proximity. Additionally, when the molecular mass or weight of the molecule increases, the hydrocarbon portion of the molecule, which is hydrophobic (“water-hating”), becomes larger.
Water is miscible with ethanol, methanol, n-propyl, isopropyl, and t-butyl alcohols, among other alcohols. Furthermore, the OH group in alcohols is polar, which causes them to be water-soluble in nature. The alkyl chain, on the other hand, is non-polar, and as a result, it reduces the solubility of alcohol in water.
The Acidity of Alcohol
Alcohols react with active metals such as sodium, potassium, and other elements to generate the alkoxides that are formed. The acidic character of alcohols is indicated by their chemical interactions. The polarity of the –OH bond is responsible for the acidic character of alcohol. When an electron-donating group is linked to the hydroxyl group, the acidity of alcohols reduces due to the rise in electron density on the oxygen atom caused by the electron-donating group. As a result, primary alcohols tend to be more acidic than secondary and tertiary alcohols in most cases. Because of the existence of unshared electrons on the oxygen atom, alcohols can also operate as Bronsted bases in addition to other compounds.
Conclusion
At room temperature, the vast majority of ordinary alcohols are clear, colourless liquids. Free-flowing liquids with fruity aromas, methylated spirits, ethanol, and isopropylated spirits are all types of alcohol. When it comes to higher alcohols, those with 4 to 10 carbon atoms have a thick or oily consistency, and their aromas are more strongly fruity. Compared to other hydrocarbons with equal molecular weights, alcohols have greater boiling points on average than these other hydrocarbons. Intermolecular hydrogen bonding exists between the hydroxyl groups of alcohol molecules, and this is what causes this phenomenon to occur.
