Chemical Properties of Primary Alcohols

A class of chemical compounds is defined by the presence of one or more hydroxyl (-OH) groups linked to the carbon atom of an alkyl group; alcohol (hydrocarbon chain). When compared to water (H₂O), alcohols can be thought of as organic derivatives in which one of the hydrogen atoms has been replaced by an alkyl group, which is commonly denoted by the letter R in organic structures. For example, in ethanol (or ethyl alcohol), the alkyl group is represented by the ethyl group, which is represented by the symbol CH₂CH₃.

Depending on how closely the carbon of the alkyl group is bound to the hydroxyl group, alcohols can be divided into three categories: primary, secondary, and tertiary. At room temperature, the vast majority of alcohols are colorless liquids or solids. Alcohols with a low molecular weight are highly soluble in water; as the molecular weight of the alcohol increases, it becomes less soluble in water, and the boiling temperatures, vapor pressures, densities, and viscosities of the alcohol increase as a consequence.

Chemical Properties of Primary Alcohols

• Because of the breakage of the O-H and C-O bonds in primary alcohols, a wide range of spontaneous chemical reactions can occur.
• Overall, alcohols are more acidic than alkenes and amines, but less acidic than hydrogen halides due to their higher acidity.
• Among the alcohols that are miscible in water are ethanol, methanol, and propanol.
• Alcohols are classified into two groups: hydrophobic and hydrophilic.
• When exposed to oxygen, alcohol burns, releasing water and carbon dioxide into the atmosphere. They burn easily and cleanly, and they don’t produce any soot when burned.
• Primary alcohols can be easily oxidized to ketones or aldehydes, and oxidizing agents such as acidified potassium manganate or acidified potassium dichromate are utilized to accomplish this oxidation. The carboxylic acids are formed as a result of the additional oxidation of the ketones and aldehydes.
• In addition to producing esters through interaction with carboxylic acids, they can also be dehydrated to form alkenes through heating with strong sulfuric acids. This reaction results in the production of water as a byproduct. When alcohols are treated with protic acids, they often dehydrate as a result of the process.

Oxidation Primary Alcohol

Depending on the reaction conditions, primary alcohols can be oxidized to either aldehydes or carboxylic acids. With regard to the creation of carboxylic acids, the alcohol is first converted to an aldehyde, which is then further converted to acid.

Aldehydes Are Formed as A Result Of Partial Oxidation

It is possible to produce an aldehyde if you use an excessive amount of alcohol and distill the aldehyde as soon as it is formed.

Because of the excessive amount of alcohol present, there is not enough oxidizing agent present to complete the second stage of the reaction. Remove the aldehyde from the system as soon as it is created, so that it does not accumulate and wait to be oxidized in the first place.

       3CH₃CH₂OH + 2Cr₂O₇^2- + 8H⁺→ 3CH₃COH + 2Cr³⁺ +7H₂O

You would get the aldehyde ethanal (CH₃CHO) if you utilized ethanol as the main alcohol, which is a common practice.

Carboxylic Acids Are Formed After Complete Oxidation

It is necessary to employ an excessive amount of the oxidizing agent and to ensure that the aldehyde generated as a by-product of the halfway process remains in the mixture.

During the heating process, the alcohol is heated under reflux with an excessive amount of the oxidizing agent. When the reaction is complete, the carboxylic acid is separated from the other components.

       3CH₃CH₂OH + 2Cr₂O₇^2- + 16H⁺→ 3CH₃COOH + 4Cr³⁺ +11H₂O

Dehydration Of Primary Alcohol

The E2 pathway is responsible for the dehydration of primary alcohols. A proton from sulfuric acid (H₂SO₄) receives two electrons from the hydroxyl oxygen, resulting in the formation of an alkyloxonium ion. The conjugate base, HSO₄^–, then interacts with one of the neighboring (beta) hydrogen atoms, resulting in the formation of a double bond between the alkyloxonium ion and the adjacent hydrogen atom.

Alkoxide

The organic functional group known as alkoxide is created when a hydrogen atom is removed from an alcohol’s hydroxyl group as a result of the interaction of the alcohol with a metal. It is the conjugate base of the alcoholic compound ethanol.

Alkoxides are represented by the formula RO-, where R denotes the organic substituent derived from alcohol. Alkoxides are strong bases that also serve as excellent ligands (when R is relatively small). In general, alkoxides are unstable in protic solvents, but they can exist as intermediates in chemical reactions. Transition metal alkoxides are utilized as catalysts as well as to create coatings for various applications.

Conclusion

Alcohols are acidic in their natural state. They react with metals such as sodium, potassium, and other similar elements. In this case, it is owing to the polarity of the connection formed between hydrogen and an oxygen atom in the hydroxyl group of the compound. The acidity of primary alcohols is higher than that of secondary and tertiary alcohols.

A pure ethanol solution has a boiling point of 78.5° C and is a flammable, colorless liquid. Because of its low melting point of -114.5° C, it can be utilized in antifreeze products such as antifreeze. A lovely aroma that reminds one of whisky permeates the air.