Table of Contents
Alcohol and Phenols: Alcohols are carbon atoms with a hydroxyl group (- OH) linked to one of their carbon atoms. Enols are compounds with a hydroxyl group linked to a double bond’s unsaturated carbon atom. Alkyl, alkenyl, alkynyl, cycloalkyl, and benzyl are all saturated carbons. On the other hand, suppose a hydroxyl group is connected to a benzene ring. These chemicals are referred to as phenols.
Monohydric alcohols (containing one OH group), dihydric alcohols (containing two OH groups), and trihydric alcohols (containing three OH groups) are the three types of alcohols.
Alcohol is employed in industry as well as in everyday life. Ethanol, for example, is a commonly used spirit for polishing wooden furniture. Sugar, cotton, and paper are all made up of group-containing compounds. Phenols may be found in a wide range of key polymers, such as Bakelite, and medications like Aspirin.
Functional Group Structure
The oxygen of the hydroxyl group is attached to carbon in the structure of alcohols via a sigma bond, which is produced by the overlap of an sp3 hybridized orbital of C with an sp3 hybridized orbital of oxygen.
1. Boiling Point:
Alcohols and phenols have higher boiling points as the number of carbon atoms rises (increase in van der Waals forces). As branching grows, the boiling point of alcohol drops (decrease in Van der Waals forces due to decrease in surface area). The -OH group in alcohols and phenols has a hydrogen atom linked to an electronegative oxygen atom. As a result, it can generate stronger intermolecular hydrogen bonds than the amine.
Due to strong intermolecular hydrogen bonding, alcohols and phenols have greater boiling temperatures than other types of chemicals, such as hydrocarbons, ethers, and haloalkanes/haloarenes, amines with comparable molecular weights.
They have lower boiling points than carboxylic acid, which has a stronger hydrogen bond. Because van der Waals forces diminish as size reduces, boiling temperatures for isomeric alcohols decline as branching increases. Primary alcohol > secondary alcohol > tertiary alcohol is the boiling point order.
The boiling point of ethers is relatively low, equivalent to that of alkanes of comparable molecular mass, due to their reduced dipole moment and lack of H-bonding.
Because of their propensity to establish hydrogen bonds with water molecules, alcohols and phenols are soluble in water. As the size of the hydrophobic group grows larger, solubility declines (R). Alcohol in higher quantities is insoluble. Branching promotes solubility by reducing the surface area of the nonpolar hydrocarbon component.
n-butyl alcohol < isobutyl alcohol < sec-butyl alcohol < tert-butyl alcohol.
Characterization of Alcohols-Analysis
- Alcohols are dissolved by cold concentrated sulfuric acid. Alkenes, amines, practically all oxygen-containing chemicals, and readily sulfonated compounds all have this feature. (Alcohol, like other oxygen-containing chemicals, creates oxonium salts, which dissolve in sulfuric acid, which is very polar.)
- Alcohols are not oxidized by cold dilute, neutral permanganate (although primary and secondary alcohols are oxidized by permanganate under more vigorous conditions). As we’ve seen, alcohols can include contaminants that oxidize under these circumstances. Therefore, the permanganate test should be performed with care.
- The colour of bromine in carbon tetrachloride is unaffected by alcohol. They are distinguished from alkenes and alkynes by this property.
- Characterization benefits from developing hydrogen gas from alcohol interactions with sodium metal.
- The development of an ester commonly indicates the presence of a hydroxide group in a molecule after treatment with an acid chloride or anhydride. Some esters have a pleasant odour, while others have high melting points and can be used to distinguish between them.
- The Lucas test identifies whether alcohol is primary, secondary, or tertiary based on the differential reactivity of the three classes toward hydrogen halides. The Lucas reagent, a strong hydrochloric acid, and zinc chloride solution, is soluble in alcohols with less than six carbons.
- The creation of chloride from alcohol is shown by the cloudiness that develops as the chloride separates from the solution. As a result, the amount of time it takes for cloudiness to occur is a measure of how reactive the alcohol is.
- The Lucas reagent interacts with tertiary alcohol rather instantly. Secondary alcohol responds in five minutes. The main alcohol does not react much at room temperature. Benzyl alcohol and allyl alcohol react as swiftly as tertiary alcohols with the Lucas reagent. In contrast, allyl chlorides are soluble in the reagent.
What Is the Best Way to Name Alcohol?
- The name of the alcohol is one of the questions that pupils have difficulty answering. So, we’re here to assist you in deciphering the nomenclature of alcohol. The steps to identifying alcohol are outlined below.
- To begin, seek the carbon atoms present in the longest carbon chain with the OH group.
- Now you must utilize the prefix to determine the location of the carbon atom holding the OH bond and then add “ol” at the end. Take the number from the end of the chain nearest to the alcohol group.
- Then, according to the formula, utilize numbers, di-, tri-, and so on.
What are some of the most important alcohol and phenols reactions?
According to the JEE syllabus, all reactions involving the preparation of phenols are very important; other important reactions include electrophilic aromatic substitution reactions of phenols, such as Kolbe's and Reimer Tiemann reactions, dehydration reactions of alcohol, and oxidation reactions of alcohol, among others.
Is there a reaction between alcohol and phenol?
All of the reactions resulted in a significant quantity of coke production. Under the same reaction conditions, the alkylation of phenols by alcohols produced a mixture of 0- and C-alkylated products.
Q. What are some of the most crucial aspects of “alcohol and phenols” to cover?
Ans: Alcohols and phenols are hydrocarbons with hydroxyl groups instead of one or more hydrogen atoms. If we look at prior year JEE question papers, we can see that at least two to three questions from this chapter are asked practically every year. The following are the main themes covered in this chapter:-
- Alcohol’s acidity and phenols’ acidity
- Alcohol’s solubility in water
- Alcohol boiling points
- Phenolic ring resonance
- Dehydration of primary, secondary, and tertiary alcohols in order.
- In phenols, the hydroxyl functional group has a strong impact.