Chapter 10 Alcohols, Phenols and Ethers

Chapter 10 Alcohols, Phenols and Ethers Introduction of Alcohol, Preparation and Properties Introduction of Alcohol ➤ Oxygen containing compound ➤ General Method of Preparation Monohydric alcohol ➤ Physical Properties of Alcohol ➤ Chemical Properties of Alcohol Differentiation Methods of Alcohol Phenols (Introduction, Preparation Method and Properties) H H Phenols-General Method of Preparation H ➤ Physical Properties of Phenols Chemical Properties of Phenols Phenols Reaction of OH Group Phenols Reaction of Benzene Ring Test of Phenol and Uses of Phenol Ethers INTRODUCTION OF ALCOHOL, PREPARATION AND PROPERTIES Introduction of Alcohol Alcohols feature oxygen atoms with sp³ hybridization, but there's a notable difference in bond angles: the COH angle in methanol (108.9°) is notably greater than the HOH angle in water (104.5°). This discrepancy arises from the relatively larger size of the methyl group compared to a hydrogen atom. The bulkier methyl group offsets the bond angle compression that results from the nonbonding electron pairs of oxygen. While the OH bond lengths are similar in both water and methanol (0.96 Å), the CO bond is notably longer (1.4 Å), which reflects the greater covalent radius of carbon compared to hydrogen. 104.5° water H 108.9° H Methyl alcohol (1) Aliphatic Hydroxy Derivatives H Hydroxy derivatives in which-OH is directly attached to sp³ C (Alcoholic compounds). (II) Aromatic Hydroxy Derivatives Hydroxy derivatives in which-OH is directly attached to sp² C or benzene ring (Phenolic compounds). Aliphatic Hydroxy Derivatives (a) Classification according to number of -OH groups (i) Monohydric [one-OH] CH3CH2-OH (ii) Dihydric [two-OH] CH2-CH2 (iii) Trihydric [three-OH OH-OH CH2-CH-CH2 OH OH OH 1 (IV) Polyhydric [N-OH] CH2 OH OH OH (b) Classification according to nature of carbon (1) por 1 deg - alcohol C*H_{3}*C*H_{2} - OH (ii) s or 2 deg - -alcohol (CH 3 ) 2 CH - OH (iii) tor 3 deg -alcohol Alcohols (CH 3 ) 3 C - OH Structure of Alcohol CH2 -CH 1 Alcohols exhibit a bent molecular structure. The carbon atom bonded to the oxygen atom in the -OH group is s * p ^ 3 hybridized, and the central oxygen atom is also in an s * p ^ 3 hybridization state. The bond angle is approximately 108.50 degrees. In the process of sp³ hybridization, the oxygen atom's 2s ^ 2 2p * x ^ 2 2py, and 2p * z ^ 1 orbitals combine to form sp³ hybrid orbitals. sp³ - sp3 :0: sp³-1 108.5 deg 2p_{x} 2p_{y} 2p_{x} HC sp S * p ^ 1 hybridi station Structure of C*H_{3} OH H 1 2s Non-bondinge pair σ Bond S * p ^ 3 atom Bond 108.5 deg Hatom Hybridised Orbitals S * p ^ 3 Catom H H H Out of these four orbitals, two contain one electron each, while the other two contain two electrons each. The orbitals with two electrons do not actively participate in bonding. The remaining two half-filled orbitals form sigma (6) bonds with the s-orbitals of hydrogen atoms and the hybridized orbital of carbon atoms (O-C). Due to the influence of the lone pair, the bond angle of the tetrahedral oxygen atom is slightly less than the usual tetrahedral structure, measuring 109.028 degrees. 2 (1) Reaction with halogen acid R - C*H_{2} - OH + HCl R-CH2-CI+ H2O ZnCl 2 Delta , R_{2}*CH - OH + HCl R2CH-CI+ H2O 20 alcohols ZnCl 2 Delta , Reactivity of the acids is HI > HBr > HCI > HF (ii) Reaction with inorganic acids R + 0 - N = 0 + H_{2}*O R - OH + H -O- N = 0 0 0 Nitric acid R-OH + HHSO4 ← Alkyl nitrate R - HS*O_{4} + H_{2}*O Alkyl hydrogen sulphate (iii) Reaction with phosphorous halides R-CI+ POCI₂ + HCI (SOCl2) 3R - OH + PC*l_{3} R - OH + PC*l_{5} 3RCl + H_{3}*P*O_{3} (iv) Reaction with thionyl chloride R-OH + SOCI2 Pyridine (gas) R - Cl +SO 2 hat T +HCl (v) Reaction with NH3: Alumina (A*l_{2}*O_{3}) is used as dehydrating agent. R - N*H_{2} + H_{2}*O R - OH + HN*H_{2} (A*l_{2}*O_{3})/(250 deg * C) \rightarrow (vi) Reaction with halogens: Oxidation and chlorination takes place simultaneously. C*H_{3}*C*H_{2}*OH + C*l_{2}(dry) CH3CHO + 2HCI (Oxidation) CCHCHO+ 3HCI (chlorination) chloral C*H_{3}*CHO + 3C*l_{2} (C) Reaction involving complete molecule of alcohol (1) Dehydration: Removal of H2O by two types. (a) Intermolecularly removal of H2O [form ether] (b) Intramolecularly removal of H_{2}*O form alkene] C_{2}*H_{5}*OH + H_{2}*S*O_{4} → (C_{2}*H_{5}) 2 SO 4 → C_{2}*H_{5}*HS*O_{4} 100 deg * C 0 deg * C (conc.) → C_{2}*H_{5} O C₂Hs (Williamson's Synthesis) → (Elimination) C_{2}*H_{5}*HS*O_{4} 140 deg * C 170 deg * C (Alumina) C_{2}*H_{5}*OH + A*l_{2}*O_{3} → C2H5 O C2H5 → CH * 2 = C*H_{2} 350 deg * C 250 deg * C Ease of dehydration follow the order: 3 deg * ROH > 2 deg * ROH > 1 deg * ROH > C*H_{3}*OH 11