Phenols Chemistry: Nomenclature, Properties, and Uses - PDF

Phenol Phenols Are the alcohols of benzene. They are obtained by substituting one or more hydrogen atoms of the benzene ring by an –OH group, thus the -OH group is directly attached to the benzene ring. Benzene can have more than one –OH group, thus obtaining the diphenols or triphenols....

Phenol Phenols Are the alcohols of benzene. They are obtained by substituting one or more hydrogen atoms of the benzene ring by an –OH group, thus the -OH group is directly attached to the benzene ring. Benzene can have more than one –OH group, thus obtaining the diphenols or triphenols. 1,2-benzenediol Phenol o-diphenol Nomenclature of Phenols 1. To name the phenols, the -ol ending is preceded by the corresponding aromatic hydrocarbon. 2. If there are several OH groups, the carbon atoms of benzene are numbered, so that the lowest numbering is possible. 3. When naming polyphenols, the locators and corresponding prefixes must be written. 4. If you have another substituent, carbon number 1 is assigned to the OH. hydroquinone p-diphenol 2,4-dimethylphenol 1,4-benzenediol Phenol In Phenol, the OH group is directly attached to the benzene ring. Phenol is more acidic than benzyl alcohol.  Benzyl alcohol In Benzyl alcohol, the OH group is NOT directly attached to the benzene ring! It is attached to the methyl group (CH3), which is attached to the benzene ring. According to the definition of homologous series, the adjacent members of the series differ by −CH2 group. Thus Phenol and benzyl alcohol are homologous of each other.  What is Catechol? A naturally occurring & important industrial chemical. It is a crystalline compound obtained by distilling catechu. It is used as: 1,2-dihydroxybenzene  black-and-white photographic developer  dyeing fur,  rubber and plastic production  in the pharmaceutical industry It can induce glandular stomach tumors in rodents. Catechu Nomenclature of Phenols 5. When the OH group is NOT the main function, the prefix hydroxy is used- accompanied by the name of the hydrocarbon. Since Acids are more important than alcohols, in benzoic acid (benzene acid COOH), carbon 1 is assigned to the carbon that has the acid and the OH group is considered a substituent. As a substituent it is named as hydroxy and not -ol.. 2-hydroxy-4-methylbenzoic acid Nomenclature Practice 4-methyl phenol 2- nitrophenol Pentaclorophenol Nomenclature practice 3-chlorocatecol P-Aminophenol 3-chloro-1,2-benzenediol 4-Aminophenol 3-chloro-o-diphenol Physical Properties of Phenols 1. Phenols also form hydrogen bonds with each other. These hydrogen bonds cause them to have higher boiling points than equivalent alkanes. 2. They also are polar compounds, which allows them to be soluble in water.. Physical Properties of Phenols 3.Phenol is acidic: Phenol is a very weak acid. Since the oxygen of the OH group is attached to the aromatic ring with more force they are much more acidic than alcohols. It can cause blisters on the skin. 4. Phenol is quite toxic (poisonous) to humans if ingested. Blister on the skin  Uses of Phenols Phenol Phenol Disinfectant Phenol Phenol Antiseptic Germicide Local anesthetics Phenol as a disinfectant Difference between Disinfectant, Germicide & Antiseptic Disinfectant is a substance which kills germs and/or viruses from any surface. Disinfectants are used to kill germs on nonliving surfaces. Disinfectants should not be used on your skin. Examples: Hydrogen peroxide, Alcohol, Formaldehyde, Chlorine & its compounds and Phenolics. Disinfectants can contain the same types of chemicals as antiseptics but in higher concentrations! Antiseptics kill microorganisms on your skin. Examples: Ethyl alcohol & isopropyl alcohol: used to disinfect your skin before needle sticks and in hand sanitizer Halogenated phenol & Peroxide: used in mouthwash & disinfect your skin. Germicide is an agent that kills pathogenic organisms; a disinfectant. Germicides are also used to combat pests and pathogens of plants: weeds. Uses of Phenols The main application of phenol is the synthesis of phenol-formaldehyde resins and plastics, such as BAKELITE. Bakelite is used for the handle of pans. because it is a good heat insulator. It is NOT used to cover electrical cables because it is very rigid. Bakelite is used in electrical appliances because it is an electrical insulator, light and easy to mold. Uses of Phenols’ Derivatives Hydroquinone Hydroquinone and similar compounds are used as photo developers and as a skin bleach in facial creams. Photo developers Facial cream Obtaining Phenols They are also obtained in a smaller proportion from coal tar. Most phenols are industrially prepared by the same methods used in the laboratory. One of the most used synthesis processes is using Chlorobenzene with Sodium hydroxide, with heat and high pressure.. high pressure Chlorobenzene Phenol  Chemical Properties of Phenols 1. Phenols act as acidic substances with strong bases such as sodium hydroxide. This is a neutralization reaction. The salt is in this case is called sodium phenoxide, where the hydrogen of the OH is replaced by the metal sodium.. Sodium phenoxide Chemical Properties of Phenols 2. Halogenation. When phenol is treated with excess of bromine water, it produces 2,4,6-tribromophenol. Chemical Properties of Phenols 3. Nitration Phenols produce 2,4,6-trinitro phenol when they react with HNO3. + HNO3 Conc. 2,4,6-trinitro phenol Chemical Properties of Phenols 4. Oxidation reactions with potassium permanganate producing aromatic ketones.. + KMnO4 Phenol Quinone p-benzoquinone Chemical Properties of Benzyl Alcohol Oxidation reactions of Benzyl alcohol produce Benzaldehyde and then Benzoic acid