Alcohols: Nomenclature, Properties, and Reactions PDF

🍸 9/8/24, 3:18 AM Alcohols: Nomenclature, Properties, and Reactions Alcohols: Nomenclature and Properties Naming Alcohols To na...

🍸 9/8/24, 3:18 AM Alcohols: Nomenclature, Properties, and Reactions Alcohols: Nomenclature and Properties Naming Alcohols To name an alcohol, follow these steps: 1. Number the chain to get the lowest possible number for the OH group. 2. Use the suffix "-ol" for alcohols (e.g., butane -> butanol). 3. If the OH group is not the highest priority functional group, name it as a substituent (hydroxy group). Properties of Alcohols Alcohols have hydrogen bonding due to the OH group. Alcohols are not very acidic, with pKa values similar to water. To rank alcohols by acidity, consider the carbon attached to the OH group: Methyl alcohol (primary): most acidic Secondary alcohol: less acidic Tertiary alcohol: least acidic Phenol: A Special Case 🔥 Phenol is significantly more acidic than aliphatic alcohols (pKa ~ 10). This is due to resonance stabilization of the conjugate base. In the conjugate base, the negative charge is shared by 4 atoms: oxygen and 3 carbons (ortho and para positions). Substituents in the ortho and para positions have the greatest impact on the conjugate base stability. Stability of Conjugate Bases Substituent Effect on Conjugate Base Donating (e.g., amino) Destabilize Withdrawing (e.g., CF3) Stabilize Ranking Phenols as Acids 📊 https://www.turbolearn.ai/content/66a94cf0-7aec-47de-8757-4a90104fc210 1/7 9/8/24, 3:18 AM Alcohols: Nomenclature, Properties, and Reactions Phenol Substituent Effect on Acidity 1 CF3 (para) Strongest acid 2 CF3 (meta) Weaker acid 3 OCH3 (ortho) Weaker acid 4 NH2 (ortho) Weakest acid Reactions of Alcohols 🔩 Substitution Reactions Reacting an alcohol with a strong acid (e.g., HI, HBr, HCl) allows the OH group to leave as water, a good leaving group. The reaction proceeds via an SN1 mechanism in a protic solvent. A good leaving group is one that is stable after leaving, such as Cl-, Br-, or I-.## SN1 and SN2 Reactions 🔄 SN1 vs SN2 Mechanisms SN1 is the preferred mechanism for tertiary and secondary alcohols. Primary alcohols cannot undergo SN1 due to the formation of a primary carbocation, which is unstable. Reactivity of Alcohols Alcohol Reactivity with HCl and ZnCl₂ Tertiary Fast (immediate reaction) Secondary Moderate (reaction within a few minutes) Primary Slow (no reaction at room temperature) Lucas Reagent The Lucas reagent is a mixture of HCl and ZnCl₂ used to determine the type of alcohol present. It reacts with alcohols to form a carbocation, which is then stabilized by the formation of a chloride ion. SN2 Reaction with PBr₃ and Pyridine https://www.turbolearn.ai/content/66a94cf0-7aec-47de-8757-4a90104fc210 2/7 9/8/24, 3:18 AM Alcohols: Nomenclature, Properties, and Reactions This reaction involves the replacement of the hydroxyl group with a bromine atom. It occurs through an SN2 mechanism, resulting in Walden inversion. The pyridine acts as a base, deprotonating the hydrogen atom. Sulfonate Esters Sulfonate esters are formed by reacting an alcohol with a sulfonate group. They are often abbreviated as Ts (toluenesulfonyl) or Ms (methanesulfonyl). These esters are good leaving groups due to the stability of the sulfonate group, which is stabilized by resonance. Elimination Reactions Elimination reactions involve the formation of an alkene from an alcohol. They are typically acid-catalyzed and occur through an E1 or E2 mechanism. The preferred mechanism is E1, but primary alcohols may undergo E2. Acid-Catalyzed Dehydration This reaction involves the formation of an alkene from an alcohol using an acid catalyst. The acid catalyst is typically H₂SO₄ or H₃PO₄. The reaction occurs through an E1 mechanism. Oxidation of Alcohols 🔥 Definition Oxidation is the process of increasing the number of bonds to oxygen or any other more electronegative element. Oxidation of Primary, Secondary, and Tertiary Alcohols Alcohol Number of Hydrogens Steps of Oxidation Primary 2 2 Secondary 1 1 Tertiary 0 0 https://www.turbolearn.ai/content/66a94cf0-7aec-47de-8757-4a90104fc210 3/7 9/8/24, 3:18 AM Alcohols: Nomenclature, Properties, and Reactions Oxidizing Agents Chromic acid (CrO₃) is a strong oxidizing agent that can oxidize primary alcohols to carboxylic acids. Weaker oxidizing agents may only oxidize primary alcohols to aldehydes. Jones Reagent The Jones reagent is a mixture of chromic acid and sulfuric acid. It is used to oxidize alcohols to carboxylic acids or aldehydes.## Oxidation of Alcohols 🧪 Chromic Acid Chromic acid is a strong oxidizing agent that converts alcohols to carboxylic acids. It oxidizes primary alcohols to aldehydes and then further to carboxylic acids, whereas secondary alcohols are oxidized to ketones. PCC (Pyridinium Chlorochromate) PCC is a weaker oxidizing agent that oxidizes primary and secondary alcohols one step. It is a chromium reagent that only goes one step, unlike chromic acid. Oxidizing Agent Primary Alcohols Secondary Alcohols Chromic Acid Aldehyde → Carboxylic Acid Ketone PCC Aldehyde Ketone Jones Reagent (Chromic Acid) Test The Jones reagent test is used to distinguish between primary, secondary, and tertiary alcohols. Chromic acid is orange in color and turns green when it reacts with primary or secondary alcohols. Nomenclature for Ethers and Epoxides 📚 Ethers Ethers have an oxygen atom between two carbon chains. An ether is a type of organic compound that has an oxygen atom between two carbon chains. Common Name IUPAC Name Diethyl ether Ethoxypropane https://www.turbolearn.ai/content/66a94cf0-7aec-47de-8757-4a90104fc210 4/7 9/8/24, 3:18 AM Alcohols: Nomenclature, Properties, and Reactions Common Name IUPAC Name Ethyl propyl ether Ethoxypropane Ethers are often used as solvents and are fairly inert. Epoxides Epoxides have three different conventions for naming. An epoxide is a type of organic compound that has an oxygen atom in a three-membered ring. Convention Example Alkene oxide Propene oxide or propylene oxide Substituent Epoxypropane Oxirane 2-Methyloxirane Epoxides are often made from alkenes and have multiple ways of being named. Reactions of Ethers ⚗️ Williamson Ether Synthesis The Williamson ether synthesis is a method of making ethers through an SN2 reaction. The reaction involves deprotonating an alcohol to make a strong nucleophile, which then reacts with a primary alkyl halide. Step Reaction 1 Deprotonate alcohol with sodium or potassium hydride 2 SN2 reaction with primary alkyl halide The Williamson ether synthesis is an SN2 reaction that requires a strong nucleophile to initiate the reaction. Reaction with Strong Acids Ethers can react with strong acids, such as HBr or HI, to form products. However, this reaction is not as important as the Williamson ether synthesis.## Epoxides and Ethers in Nucleophilic Substitution Reactions 💡 Protonation of Epoxides https://www.turbolearn.ai/content/66a94cf0-7aec-47de-8757-4a90104fc210 5/7 9/8/24, 3:18 AM Alcohols: Nomenclature, Properties, and Reactions When epoxides react with HBr, the oxygen atom is protonated, turning a bad leaving group into a good one. This allows the oxygen to leave from either side, resulting in two alkyl halides as products. Differences in Nucleophilic Substitution Reactions Epoxides: Have a fair amount of ring strain, which can be relieved by a nucleophile attack. Ethers: Do not have ring strain, but can still undergo nucleophilic substitution reactions. Nucleophilic Substitution on Epoxides Acid-Catalyzed: The epoxide is protonated, making the oxygen atom a good leaving group. The nucleophile attacks the more substituted carbon. Base-Catalyzed: The epoxide is not protonated, and the nucleophile attacks the less substituted carbon. Key Points to Recognize Acid-Catalyzed: Look for the presence of acid (e.g. H₂SO₄, H⁺). Base-Catalyzed: Look for the absence of acid and the presence of a strong base (e.g. NaOCH₃). Mechanism of Acid-Catalyzed Nucleophilic Substitution on Epoxides The protonated epoxide is attacked by the nucleophile, resulting in the opening of the epoxide ring and the formation of a product with a new bond to the nucleophile. Step Reaction 1 Epoxide protonation 2 Nucleophile attack on more substituted carbon 3 Ring opening and product formation Mechanism of Base-Catalyzed Nucleophilic Substitution on Epoxides The epoxide is attacked by the nucleophile, resulting in the opening of the epoxide ring and the formation of a product with a new bond to the nucleophile. Step Reaction 1 Nucleophile attack on less substituted carbon https://www.turbolearn.ai/content/66a94cf0-7aec-47de-8757-4a90104fc210 6/7 9/8/24, 3:18 AM Alcohols: Nomenclature, Properties, and Reactions Step Reaction 2 Ring opening and product formation https://www.turbolearn.ai/content/66a94cf0-7aec-47de-8757-4a90104fc210 7/7