Organic Chemistry: Alcohols - Reactions, Preparation, and Properties PDF

Ok, here is the text from the images converted into a markdown format. ### Alcohols * They are compounds containing one or more $(OH)$ groups and are classified according to the number of $(OH)$ groups into: I) Monohydric alcohols: contain one $(OH)$ group. eg: $CH_3CH_2OH$ II) Dih...

Ok, here is the text from the images converted into a markdown format. ### Alcohols * They are compounds containing one or more $(OH)$ groups and are classified according to the number of $(OH)$ groups into: I) Monohydric alcohols: contain one $(OH)$ group. eg: $CH_3CH_2OH$ II) Dihydric alcohols: contain two $(OH)$ groups. III) Polyhydric alcohols: contain more $(OH)$ groups. $CH_2-CH-CH_2$ | | | $OH OH OH$ ### 1) Monohydric Alcohols: * They can be classified as $1°$, $2°$ or $3°$ alcohol depending on the type of carbon atom to which the $(OH)$ group is attached. **Nomenclature of Alcohols:** The image shows three molecules * First molecule: T: n-Butyl alcohol I: 1-Butanol (1° alcohol) * Second molecule: T: Isopentyl alcohol I: 3-Methyl-1-butanol (1° alcohol) * Third molecule: T: neo-Pentyl alcohol I: 2,2-Dimethyl-1-propanol (1° alcohol) The image shows three molecules * First molecule: T: sec-Butyl alcohol I: 2-Butanol (2° alcohol) * Second molecule: T: ter-Pentyl alcohol I: 2-Methyl-2-butanol (3° alcohol) * Third molecule: I: 2-Methyl-1-butanol (1° alcohol) The image shows two molecules * First molecule: I: 2-Methyl-3-pentanol (2° alcohol) * Second molecule: I: 3-Bromo-2,4-dimethyl-4-penten-2-ol (3° alcohol) ### Preparation: 1. From Alkenes: Q: How can you convert propene to 2-propanol. $CH_3-CH=CH_2 \xrightarrow{H_2O/H^+} CH_3-CH-CH_3$ | OH 2. From Alkyl Halides: Q: How can you convert: $CH_4 to CH_3OH$ $CH_4 + Cl_2 \rightarrow CH_3Cl + HCl$ $CH_3Cl \xrightarrow{aq. KOH} CH_3OH$ ### 3) From Carbonyl Compounds: i) Via Reduction:\ e.g.: The drawing illustrates some reagents: Strong reducing agent, Moderate reducing agent and Weak reducing agent, and their reactions. ii) Via Grignard Reagent: The drawing illustrates Reaction with formaldehyde gives 1° alcohol. Reaction with any Aldehyde gives 2° alcohol. Reaction with any Ketone gives 3° alcohol. **e.g.:** The drawing illustrates Reaction of Two Moles of Grignard with Fromate ester gives 2° alcohols. Reaction of Two Moles of Grignard with any other ester gives 3° alcohols. ### Physical properties: * Lower alcohols are miscible with water due to H-bonds between alcohols and water. * As the length of the hydrocarbon portion of the alcohol molecule increases, the water solubility of the alcohol decreases. * Also, alcohols have high boiling points due to intermolecular H-bonding. ### Reactions A) Reactions at O-H bond: 1. Reaction with Active Metals: **e.g.:** i) $OH + Na \rightarrow ONa + 1/2H_2$ Sodium ethoxide ii) $3OH+AL\rightarrow (O)_3 Al + 3/2 H_2$ Aluminium ethoxide iii) $OH + K \rightarrow O K + 1/2 H_2$ Pot. ter-butoxide 2) Ester formation: * Alcohols form esters when react with inorganic or organic acids with liberation of water molecule, whose (OH) comes from the acid and (H) comes from alcohol. i) Esters of Inorganic Acids ($H_2SO_4$ $HNO_3$ and e.g.$H_3PO_4$): CH3CH2OH + HO-S-OH $\rightarrow$ H2CH2CO-S-OH $\rightarrow$ H2CH2CO-S-OCH2CH | 0 iii) Ester of Organic Acids (e.g. Carboxylic Acids): $CH_3COOH + HO-CH_2CH_3 +H_2SO_4 CH_3COOCH_2CH_3$ Acetic acid Ethyl acetate Ethanol | ### B) Reactions at C-OH bond: **Reaction with Hydrogen Halides (HX):** Alcohols react with Hydrogen Halides to form Alkyl Halides $R-OH + HX \rightarrow RX + H_2O$ $X = Cl, Br, I$ ### Lucas Test $R-OH + HCl \xrightarrow{ZnCl_2} RCl + H_2O$ * Lucas reagent (a mixture of Conc. $HCl$ and $ZnCl_2$) * It is used to differentiate between 1º, 2º and 3° alcohols. * It depends on the difference in reactivity of these three classes of alcohols towards $HCl$ to form the corresponding $RCl$. * Formation of the $RCl$ is indicated by the cloudiness that appears when the $RCl$ separates from the solution. The drawing illustrates with chemical reactions for (3º Alcohol forms Cloudiness immediately). (2° Alcohol forms Cloudiness within five minutes.) (1° Alcohol does not react at room temperature but needs heat) **Mechanism:** Shows the mechanism using formula and reagents ZnCl2 ### C) Reactions at whole compound: 1. Oxidation: i) $H_3C-CH_2OH \xrightarrow[]{[O} H_{3C-CHO}$ gives Aldehyde on Mild Oxidation.\ $H_3C-CH_2OH \xrightarrow[]{KMnO_4 or K_2Cr_2O7} H_3C-COOH$ gives Carboxylic Acid on Strong Oxidation Note: PCC: Pyridinium ChloroChromate $[C_5H_5NH]^+[CrO_3Cl]^-$ ii) Shows reaction of $2°$ alcohol. $2°$ alcohol gives Ketones on Oxidation. iii) NO Reaction, $3°$ alcohol. 2) Dehydration: i) $CH_3CH_2OH \xrightarrow[]{c.H_SO_4/180°C} H_2C=CH_2$ Ethene -H_2O ii) $2CH_3CH_2OH \xrightarrow[]{c.H_SO_4/140°C} CH_3CH_2OCH_2CH_3$ Diethyl ether -H_2O ### II) Polyhydric Alcohols They contain two or more (OH) groups. **Nomenclature of Polyhydric Alcohols:** The image shows three molecules * First molecule: T: Ethyeneglycol I: 1,2-Ethandiol * Second molecule: T: Propyleneglycol I: 1,2-Propanediol * Third molecule: T: Glycerol I: 1,2,3-Propanetriol **Preparation of Glycerol:** Shows the preparation of glycerol formula $\approx H_3{C−C=CH}_2Cl_2NaOH \over 50θ℃−−−→ \approx H_3{C−C=CH}_2HOH{_2}C−C=CH_2+HOCl$ Preparation of Glycerol. Show the formula with steps to Glycerol. Reactions: **Pinacole Rearrangement:** is Upon treatment of 2,3-dimethyl-2,3 butanediol (Pinacol) with mineral acids, such as $H_2SO_4$ , it yields methyl ter-butyl ketone (Pinacolone) due to carbocation rearrangement as follows: Shows the mechanism using formula and reagents H Formula mechanism with steps to Pinacol ### Revision Questions: 1. Convert: Methane to Ethanol. 2. How can you differentiate between: 2-methyl-2-pentanol and 2-methyl-1-pentanol. 3. Draw: 3-Isopropyl-4,4-dimethyl-5-heptyn-2-ol.