Alcohols: Organic compounds containing hydroxyl (-OH) group as a functional group bonded to a saturated carbon atom.
Example: CH3OH (Methanol)
Phenols: Compounds in which the hydroxyl group is directly attached to an aromatic ring.
Example: C6H5OH (Phenol)
Ethers: Compounds that contain an oxygen atom bonded to two alkyl or aryl groups.
Example: CH3OCH3 (Dimethyl ether)
Classification of Alcohols
Primary (1°): The carbon atom bonded to the -OH group is bonded to only one other carbon atom.
Example: Ethanol CH3CH2OH
Secondary (2°): The carbon atom bonded to the -OH group is bonded to two other carbon atoms.
Example: Isopropanol CH3CHOHCH3
Tertiary (3°): The carbon atom bonded to the -OH group is bonded to three other carbon atoms.
Example: Tert-butanol (CH3)3COH
Phenols: Typically not classified in the same way as alcohols since the -OH is always attached to an aromatic ring.
Ethers: Symmetrical (Simple) Ethers: Same alkyl groups on both sides of the oxygen.
Example: Dimethyl ether CH3OCH3
Unsymmetrical (Mixed) Ethers: Different alkyl or aryl groups on either side of the oxygen.
Example: Ethyl methyl ether CH3OCH2CH3
Alcohols: Named with the suffix “-ol” added to the name of the parent alkane.
Example: CH3CH2OH is Ethanol.
Phenols: The word “phenol” itself is used if there are no substituents. If substituents are present, their positions are indicated using numbers.
Example: C6H4(OH)(CH3) can be named as m-cresol where the methyl group is meta to the hydroxyl group.
Ethers: In the common naming system, name the two alkyl or aryl groups alphabetically and add “ether”.
Example: CH3OCH2CH3 is ethyl methyl ether. In the IUPAC system, it’s named as alkoxyalkanes. For example, the above can be named as methoxyethane.
Preparation of Alcohols
CH2=CH2 + H2O → CH3CH2OH (in the presence of acid)
From Grignard Reagents:
CH3MgBr + H2O→ CH4 + Mg(OH)Br
Reduction of Carbonyl Compounds: Using reducing agents like LiAlH4 or NaBH4.
RCHO + 2[H] → RCH2OH
Also Check – Acids and Bases Formula: Types of Reaction
Preparation of Phenols
From Halobenzenes: Using aqueous NaOH at high temperatures (called the Dow process).
C6H5Cl + NaOH → C6H5OH + NaCl
From Benzene Sulphonic Acid: Through fusion with NaOH.
C6H5SO3H + 3NaOH → C6H5OH + 3NaHSO3
Also Check – PH of Weak Acid Formula
Physical and Chemical Properties of Alcohols and Phenols
Alcohols and phenols have higher boiling points than their corresponding hydrocarbons due to hydrogen bonding.
Phenols are more acidic than alcohols due to the delocalization of the negative charge over the aromatic ring in the phenoxide ion.
Reaction with Halides:
Alcohols react with halide ions in the presence of acids to form haloalkanes.
ROH + HX → RX + H2O
This is termed as the Lucas Test when using anhydrous ZnCl2 with alcohols to distinguish between primary, secondary, and tertiary alcohols.
Alcohols react with carboxylic acids to form esters in the presence of an acid catalyst.
RCOOH + R′OH → RCOOR ′ + H2O
While secondary alcohols can be oxidized to ketones, primary alcohols can be converted to aldehydes and then to carboxylic acids. Alcohols in the tertiary stage do not simply oxidize.
Phenol, when treated with chloroform in the presence of aqueous NaOH, results in the formation of salicylaldehyde. This reaction involves the formation of dichlorocarbene.
C6H5OH + CHCl3 + 4NaOH → C6H4CHO(OH) + 3NaCl + 3H2O
Williamson Ether Synthesis:
An alcohol is first converted into a sodium alkoxide, which then reacts with an alkyl halide to form an ether.
RONa + R ′ X → ROR ′ +NaX
Alcohols, Phenols, and Ethers Formula FAQs
Q1. Which is more acidic: alcohol or phenol?
Q2. How is ethyl ether prepared from alcohols?
Ans. By dehydration of alcohols using concentrated sulfuric acid (Williamson ether synthesis).
Q3. What is the common name for dimethyl ether?
Ans. Wood spirit.
Q4. Which reacts more readily with sodium: alcohol or phenol?
Q5. What is the main product when phenol reacts with zinc dust?