NEET Study Notes for Alcohols, Phenols, and Ethers: Alcohols, Phenols, and Ethers are organic compounds. When saturated carbon bonds with the hydroxyl (-oh) group, alcohol is formed. When the hydrogen atom of a benzene molecule replaces-oh group, phenol is formed. When oxygen atom bonds with alkyl or aryl groups, ether is formed. Alcohols, Phenols, and Ethers have wide industrial and domestic applications.

• There are three sections in NEET Chemistry Syllabus- Organic, Inorganic, and Physical Chemistry. Alcohol, Phenols, and Ethers is a unit from Organic Chemistry.
• Candidates can expect around 2-3 questions from Alcohol, Phenols, Ethers, and alkyl halides in NEET 2022.

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NEET Study Notes for Alcohol, Phenols, and Ethers: Important Topics

Alcohol

Nomenclature of Alcohol

There are three systems for naming Alcohol. these are;

• Common system- As per the common system, Alcohols, are named Alkyl Alcohols Examples are Ethyl and Methyl Alcohol.
• Carbinol system- Here, alcohols are considered derivatives of methyl alcohol which can be expressed as carbinol. Examples are methyl carbinol, dimethyl carbinol, carbinol
• IUPAC System- In this system the last -e is replaced by -ol . The longest chain that starts at the end near the -Oh groups is to be numbered The remaining substituents are to be named along with their numbers.

Structure of Alcohols

Oxygen atoms in alcohol are hybridized sp3 . The hybrid atomic orbitals possess a tetrahedral disposition.

Methods of Alcohol Preparation;

• Hydrolysis of Alkyl Halides- Nucleophilic substitution reaction helps in this process. The bi-products of this process are olefins ions.
• Fermentation- Fermentation is the process of breaking down complex organic compounds by the action of enzymes into simpler organic compounds. Gases like methane and carbon dioxide are produced after this process. The process is exothermic. Yeast converts sugar to ethyl alcohol during this process.
• Reduction of Acids- In this process Acids are reduced to alcohol by lithium aluminum hydride.
• Reduction of Carbonyl compounds- Carbonyl compounds like aldehydes and ketones are used for the reduction of carbonyl compounds to alcohols. The process of catalytic hydrogenation or lithium aluminum hydride is used for reducing aldehydes to primary alcohols and ketones to secondary alcohols.
• Using Grignard Reagent- Grignard Reagent helps in the formation of monohydric alcohols of three types. Grignard reagents react with most organic compounds and several inorganic compounds.

Also Read

• NEET Study Notes on Solid State
• NEET Study Notes for Aldehydes, Ketones and Carboxylic Acid

Physical properties of Alcohol

• Boiling Point- Alcohols have higher boiling points due to the intermolecular hydrogen bonding between the alcohol molecule’s hydroxyl groups.
• Solubility- With an increase in the size of the alkyl group size, the solubility of alcohol tends to decrease.
• Acidity- Alcohols are of an acidic nature. The polarity of the -Oh bond causes the alcohol to be of acidic nature. When the electron-donating group is combined with the hydroxyl group, the acidity of alcohol decreases.

Chemical Properties of Alcohol

• Alcohol Oxidation- In the presence of oxidizing agents, alcohols demonstrate the oxidation process. This helps in the formation of aldehydes and ketones. When these undergo oxidation, carboxylic acids are formed.
• Dehydration of Alcohol- On reaction with protic acids, alcohol undergoes dehydration, and form akenes.

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Reaction of Alcohols

• Reaction with Metals- Sodium Ethoxide is produced on the reaction of sodium metal with ethanol, hydrogen gas, and sodium ethoxide.

2ROH + Na → 2RO + Na- + H2

• Reaction with Halides- The-OH group in alcohol is replaced by Halogens like chlorine and bromine

ROH + Zn + HCl → R-Cl + H2O

R2C-OH (alcohol) + HCl → R2CCL

• Reaction with Nitric Acid- Oxidation process along with the evolution of a slow gas takes place.

R-OH + HO-NO2 → R-O-NO2

• Reaction with Carboxylic Acid- Ester is formed on the reaction of alcohol with carboxylic acid when an acid catalyst is present. This process is also known as Fischer Esterification.

R-OH + R’-COOH + H+ ⇔ R’-COOR

• Dehydration of Alcohol- Ether is formed by intermolecular dehydration while alkene formation takes place due to intramolecular dehydration.

• Haloform Reaction- Haloform is produced by bonding compounds with the CH3CO group with Carbon or Hydrogen. This reaction takes place in the presence of a mild alkali.

Classification of Alcohols

Based on the number of hydroxyl groups, that are joined with carbon atoms, Alcohols can be classified into

• Monohydric Alcohols- Monohydric alcohols contain a single-OH group. Examples are-
• Dihydric Alcohols- Alcohols that consist of two -OH groups are called Dihydric Alcohol. Examples- Ethylene Glycol
• Trihydric Alcohol- Alcohols that consist of three -OH groups are called Trihydric Alcohols. Examples- Glycerol

Monohydric Alcohols can be classified based on the number of carbon atoms that are joined to the -OH group:

• Primary Alcohol- In primary alcohols, one carbon atom is joined with the -OH group.
• Secondary Alcohol- In secondary alcohols, two carbon atoms are joined with -the OH group
• Tertiary Alcohol- In tertiary alcohols, three carbons atoms are joined with the -OH group.

Uses of Alcohol

• Alcohol can be used as a solvent for varnishes, paints, and oils.
• Alcohol is used for the production of formaldehyde.
• Ethyl Alcohol can be denatured by Alcohols

Also Read

• NEET Study Notes for p block elements
• NEET Study Notes for Polymers

Phenols

Classification of Phenols

Depending on the number of hydroxyl groups that are joined with a carbon atom, phenols can be classified into

• Monohydric Phenol- Monohydric Phenols consist of a one-OH group.
• Dihydric Phenol- Dihydric Phenol consists of two -OH groups These can be classified further into ortho, -meta, -or para- derivative.
• Trihydric Phenol- Trihydric phenols consist of three -OH groups.

Nomenclature of Phenols

Phenol is the hydroxy derivative of benzene. Due to the presence of benzene ring, in substituted compounds of phenol. Common names that are used are ortho, meta, and para.

Phenols can be further classified into- monohydric, dihydric and trihydric phenols, For the IUPAC system of naming Phenol, certain rules to follow are:

• Hydroxyl groups are attached to benzene rings in the case of phenols. The number of hydroxyl groups that are attached to benzene rings helps in identifying whether prefix di, trior tetra is to be used to denote them.
• For substituted phenols, the position numbering of functional groups is done on consideration of the hydroxyl group position
• On the basis of this position, ortho, para, and meta are used for the nomenclature of phenols.

Ortho- Functional group is joined with an adjacent carbon atom.

Para- Functional group is joined with the third carbon atom

Meta- Functional group is joined with the second carbon atom

Physical Properties of Phenol

• Boiling Point of Phenol- Due to intermolecular hydrogen bonding between phenol’s hydroxyl groups, the boiling point of phenols is higher than hydrocarbons with a small molecular mass.
• Solubility- The property of solubility in phenols is rendered due to the hydroxyl groups resent. These hydroxyl groups cause the bonding of hydrogen atoms of water. Due to the increase of aryl group size, the solubility of phenol decreases.
• Acidity- On reaction with active metals like sodium, potassium, phenols form the corresponding phenoxide. These are responsible for the acidic nature of phenols.

Reaction of Phenols

• Ester Formation- Phenyl esters are formed when ArOH and chlorides/anhydrides react in the presence of a strong base.
• Hydrogenation- Cyclohexanone is formed when phenol undergoes hydrogenation.
• Electrophilic Substitution- Due to their highly reactive nature and ability to undergo oxidation as well as poly substitution, the process of electrophilic substitution takes place in phenols. The process takes place only in mild conditions.
• Halogenation- When phenols react with bromine in the presence of low polarity solvent at low temperature, monobromophenol is formed. An example of a solvent of low polarity is trichloromethane.

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Preparation of Phenols

Phenols can be produced by the following types:

• • Haloarenes- Chlorobenezene is an example of Haloarenes When the benzene ring undergoes the process of monosubstitution chlorobenzene is produced. In reaction with sodium hydroxide, sodium phenoxide is produced. Phenol is obtained by acidification of sodium phenoxide.
  • Benzene Sulphuric Acid- Benzenesulphuric is obtained in the reaction of benzene On treating this benezensulphuric with molten sodium hydroxide at a higher temperature, sodium phenoxide is produced which helps in the formation of Phenol.

• Cumene- Friedel Crafts alkylation process o benzene with propylene forms Cumene, which is an organic compound. On oxidation of cumene, cumene hydroperoxide is formed. Phenol is obtained when cumene hydroperoxide, is treated with dilute acid. The byproduct of this reaction is acetone.

Ethers

Preparation of Ethers

• Dehydration of Alcohols- In the presence of protic acids, alcohols undergo a dehydration process. Alkene and Ethers are produced in this reaction. In the presence of sulphuric acid, dehydration of ethanol is performed at 443K. Ethoxyethane is produced in this reaction.
• Williamson Synthesis- Symmetrical and asymmetrical ethers are prepared in laboratories by the process of Williamson Synthesis. Ether is produced by the reaction of alkyl halides with sodium hydroxide.

Classification of Ethers

In ethers, alkyl or aryl groups are joined with oxygen atoms, Based on this ethers can be classified into

• Symmetrical Ether- Also known as simple ether, alky,l, or aryl groups that are joined to both sides of oxygen atoms are similar. Examples- CH3OCH3, C2H5OC2H5
• Unsymmetrical Ethers- Also known as mixed ether, alkyl, or aryl groups are joined with both sides of oxygen atoms are different. Examples- CH3OC2H5, C2H5OC6H5

Nomenclature of Ethers

• Common System- When two alkyl groups are the same, ethers are dialkyl ether, Example- Diethyl ether, dimethyl ether. When two alkyl groups are different, ethers can be named alphabetically Example- ethyl methyl ether
• IUPAC System- In the IUPAC System of Nomenclature, Ethers are named Alkoxy Alkane. While the smaller group is made alkoxy, the larger group is called alkane Example- 1- methoxy propane.

Physical Properties of Ethers:

• A net dipole moment is observed in ether molecules due to C-O bond polarity.
• The boiling point of ethers is similar to alkanes. The boiling point of ethers is less in comparison to alcohols.
• Due to the hydrogen bond with water molecules, ethers are miscible in water.

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Chemical Properties of Ether

The reaction of Ethers are:

• Contact with Air- In contact with air, aliphatic ethers transform to peroxide, A red color will form when ether is shaken with an aqueous solution of potassium thiocyanate and ferrous ammonium sulfate
• Halogenation of ether- Halogenated ethers are formed on the halogenation of ether in the presence of dark, Halogens replace the hydrogen atom that is joined to the C atom.
• Electrophilic substitution reaction- Due to the presence of the alkoxy group in aromatic ethers. Like phenol, the aromatic ring gets activated.

NEET Sample MCQs on Alcohol, Phenol, and Ether

Question: On the reaction of acid and alcohol, what is formed?

1. Carboxylic Acid
2. Esters
3. Ketones
4. Ethanol

Answer: Esters

Question: Name the most acidic from the following

1. Acetic Acid
2. Trichloro acetic acid
3. Dichloro acid
4. Monochloro acetic acid

Answer: Trichloroacetic acid

Question: What is formed, on treating phenol with excess bromine water?

1. o- and p-bromophenol
2. 2, 4-bromophenol
3. 2,4, 6- tribromophenol
4. M-bromophenol

Answer: 2,4, 6- tribromophenol

Question: Which reaction is demonstrated in dehydration of alcohol?

1. Substitution reaction
2. Redox reaction
3. Addition reaction
4. Elimination reaction

Answer: elimination reaction

Question: Which alcohol does not react with Lucas's reagent?

1. sec-butyl alcohol
2. Tert-butyl alcohol
3. n- butanol
4. Isobutyl alcohol

Answer: n- butanol

Question: At low temperature—- is produced on the reaction of phenol with bromine in the presence of CS2

1. o- and p- bromophenol
2. p- bromophenol
3. m- bromophenol
4. 2, 4, 6- tribromophenol

Answer: o- and p- bromophenol

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