Alcohols, phenols and Ethers important questions Chemistry class 12th, Study notes of Chemistry

Download Alcohols, phenols and Ethers important questions Chemistry class 12th and more Study notes Chemistry in PDF only on Docsity! Alcohols, Phenols and Ethers Here are some important questions from Chapter 11 (Alcohols, Phenols, and Ethers) of Class 12th Chemistry Q1- What are alcohols? What is the difference between primary, secondary, and tertiary alcohols? Ans- Alcohols are organic compounds that contain a hydroxyl (-OH) group bonded to a carbon atom. They are classified as a type of alcohol, which is a broad class of organic compounds characterized by the presence of a hydroxyl group. The difference between primary, secondary, and tertiary alcohols is based on the number of carbon atoms bonded to the carbon atom carrying the hydroxyl group. Primary alcohols have a hydroxyl group (-OH) bonded to a carbon atom that is bonded to only one other carbon atom. Secondary alcohols have a hydroxyl group (-OH) bonded to a carbon atom that is bonded to two other carbon atoms. Tertiary alcohols have a hydroxyl group (-OH) bonded to a carbon atom that is bonded to three other carbon atoms. Primary and secondary alcohols are more reactive than tertiary alcohols, which have a higher boiling point due to the increased molecular size and reduced polarity of the hydroxyl group. Q2- What are ethers? What is the role of ethers as solvents? Ans- Ethers are organic compounds that contain an oxygen atom bonded to two carbon atoms. They are named by combining the names of the alkyl groups attached to the oxygen atom. For example, diethyl ether is an ether composed of two ethyl groups (-C2H5) bonded to the oxygen atom. The role of ethers as solvents is due to their low boiling points, low viscosities, and high volatility. These properties make them ideal for use as solvents for many organic compounds, including fats, oils, and waxes. Ethers also have a high dielectric constant, which makes them good electrical insulators. This property makes them useful as solvents in the electrical and electronics industries. Ethers are also used as solvents in many chemical reactions, including the Grignard reaction, which is a type of reaction used to synthesize alcohols and other organic compounds. They are also used as solvents in the production of pharmaceuticals and other chemicals. In addition to their use as solvents, ethers are also used as anesthetic agents due to their ability to produce unconsciousness and analgesia. Q3- What is the difference between phenols and alcohols? Ans- Phenols and alcohols are both types of organic compounds that contain hydroxyl (-OH) groups, but they have some distinct differences. The main difference between phenols and alcohols is the presence of a hydroxyl group in an aromatic ring in phenols. In phenols, the hydroxyl group is bonded to an aromatic ring, which is a type of organic ring composed of alternating single and double bonds. On the other hand, in alcohols, the hydroxyl group is bonded to a carbon atom that is part of an alkyl group, which is a chain of carbon atoms. Alcohols can be either primary, secondary, or tertiary, depending on the number of carbon atoms bonded to the carbon atom carrying the hydroxyl group. Phenols are typically more acidic than alcohols due to the presence of the aromatic ring, which makes the hydroxyl group more polarized and therefore more reactive. Phenols also tend to be more soluble in water than alcohols, due to the hydrogen bonding between the hydroxyl group and water. Q4- Explain the mechanism of the reaction between alcohols and PCl5. Ans- The reaction between alcohols and phosphorus pentachloride (PCl5) results in the formation of alkyl chlorides. The mechanism of this reaction involves the following steps: Protonation: The alcohol molecule acts as a Lewis base and donates a lone pair of electrons to the chlorine atom of PCl5, resulting in the formation of an alkoxide ion. R-OH + PCl5 → R-O-PCl4 + HCl Dehydration: The alkoxide ion reacts with another molecule of PCl5, resulting in the elimination of water and formation of a chloroalkyl phosphite intermediate. R-O-PCl4 + PCl5 → R-Cl + POCl3 + HCl Phosphorus Oxychloride Cleavage: The chloroalkyl phosphite intermediate undergoes a rearrangement reaction to form a chloroalkyl phosphonium salt. This species is then hydrolyzed to produce alkyl chloride and phosphoric acid. R-Cl + POCl3 → R+Cl-P(O)Cl3 Q-9 What is the reaction of phenols with dilute nitric acid to form nitrophenols? Ans- The reaction of phenols with dilute nitric acid to form nitrophenols is known as nitration. The reaction is represented as follows: C6H5OH + HNO3 → C6H4ONO2 + H2O In this reaction, the phenol molecule reacts with nitric acid to form a nitrophenol molecule and water. The nitration reaction involves the electrophilic substitution of one of the hydrogen atoms on the phenol molecule with a nitro group (-NO2). The nitration reaction is often carried out using dilute nitric acid to control the rate and specificity of the reaction. The nitration of phenols is an important reaction in the synthesis of a variety of compounds, including dyes, pharmaceuticals, and explosives. Q10- What are the industrial applications of alcohols, phenols, and ethers? Ans- Alcohols, phenols, and ethers have a wide range of industrial applications due to their unique physical and chemical properties. Some of the important applications of these compounds are: Alcohols: 1- Methanol is used as a solvent and as a feedstock for the production of chemicals such as formaldehyde, formic acid, and acetic acid. 2- Ethanol is widely used as a solvent, as well as a fuel and fuel additive. It is also used in the production of personal care and cosmetic products, such as perfumes and lotions. 3- Isopropyl alcohol is used as a solvent for gums, resins, and cellulose derivatives, as well as a disinfectant and cleaning agent. 4- Long-chain alcohols, such as lauryl alcohol, are used as surfactants, emulsifiers, and wetting agents in the cosmetic, detergent, and personal care industries. Phenols: 1- Phenol is used as a starting material in the production of a variety of chemicals, including phenolic resins, caprolactam, and bisphenol A. 2- Catechol is used as a building block in the synthesis of a range of chemicals, including dyes, pharmaceuticals, and resins. 3-Hydroquinone is used as a reducing agent, as well as a building block in the synthesis of dyes, plastics, and photographic developers. Ethers: 1- Diethyl ether is used as a solvent for fats and oils, as well as a starting material in the synthesis of other chemicals, such as pharmaceuticals and dyes. 2- Tetrahydrofuran is used as a solvent for a variety of chemicals, including cellulose acetate, polyvinyl chloride, and nitrocellulose. 3- Dimethyl ether is used as a clean-burning alternative to diesel fuel and liquefied petroleum gas More important questions 1- What is meant by a tertiary alcohol? How does it react with sodium metal? 2- Explain the reaction between alcohols and Lucas reagent. 3- Describe the mechanism of the reaction between alcohols and carbonyl compounds to form hemiacetals and acetals. 4- What is the difference between a hemiacetal and an acetal? 5- What is the role of a dehydrating agent in the formation of ethers? 6- Explain the reactions of ethers with concentrated sulfuric acid and aqueous sodium hydroxide. 7- Discuss the properties of phenols and how they are different from alcohols. 8- What are the different methods of preparation of phenols? 9- Explain the reactions of phenols with aqueous sodium hydroxide and sodium metal. 10- Discuss the application of phenols as disinfectants and antiseptics All the best for your exams guys