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CHAPTER 9
ALCOHOLS, PHENOLS AND ETHERS
Structure and nomenclature
Naming alcohols
R-O-R
Physical properties: Hydrogen Bonding
• methane – nonpolar compound – low boiling point
• Water and alcohol : O-H bonds are quite polar – dipole attractions exist between the molecules
• Sites of dipole attractions:
a) H of one molecule with O other molecule
b) O lone pairs with H other molecules
Uses of alcohols, ethers, phenolsa) Polyhidric alcohols:• ethylene glycol (1,2-ethanediol) – antifreeze in automobile
radiators. High boiling point 198oC, soluble in water and noncorrosive.
• glycerol (1,2,3-propanetriol) – by product of the soap manufacture, used as a humectant to preserve moistness in tabacco, cosmetics.
b) Diethyl ether• General anesthetic• Ether plays important role as solvent for organic preparation and
extraction.
c) Phenols• Medical applications: ability to act an antiseptic, local anesthetic,
skin irritancy and toxicity when ingested.
• Antioxidants: Phenol act as an antioxidants in foods and cosmetics
PREPARATION OF ALCOHOLS AND ETHERS
1) Hydration of an alkenes
2) Nucleophilic Substitution
3) Reduction of aldehydes and ketones -aldehydes are reduced to primary alcohol and ketones are
reduced to secondary alcohols
4) Grignard Synthesis of alcohols
REACTION SITES IN ALCOHOLS, PHENOLS AND ETHERS
• alcohol and phenol have both C-O and O-H polar bonds
• Ether has two C-O polar bonds
REACTION INVOLVING O-H BOND OF ALCOHOLS AND PHENOLS
A) Reaction of alcohols with Na: Reaction of the
O-H Bond
2ROH + 2Na 2RONa + H2
2C3H7OH + 2Na 2C3H7ONa + H2
B) Formation of esters: Reaction of the O-H Bonds
Alcohol form esters with both inorganic and organic acids. Example:
CH3(CH2)10CH2OH + HOSO3H
CH3(CH2)10CH2OSO3H + HOH
CH3(CH2)3OH + CH3CH2COOH
CH3(CH2)3OC(O)CH2CH3 + HOH
REACTIONS OF ROH AND ROR WITH HX: REACTION OF THE C-O BOND BY NUCLEOPHILIC SUBS.
A) Reactions of ROH with HX: SN1 & SN2 Mechanism
How to distinguish the 1o, 2o and 3o ROH
Lucas Test – ROH is treated with concentrated HCl in the presence of ZnCl2 and water to form RX and water
3o ROH – cloudy solution is instantly formed
2o ROH – cloudy solution is formed after 5-10 minutes when heated
1o ROH – no cloudy solution is formed.
B) Methods for converting ROH to RX: Reaction of the
C-O Bond
i) Thionyl chloride
ROH + SOCl2 RCl + HCl + H2O
C2H5OH + SOCl2 C2H5Cl + HCl + SO2
ii) Phosphorus trihalides (PX3) (X = Cl, Br)
3ROH + PX3 3RX + P(OH)3
3CH3(CH2)3OH + PCl3 3CH3(CH2)2Cl + P(OH)3
C) Reactions of ROR with HX: SN1 & SN2 Mechanisms
ROR + HX RX + ROH CH3CH2OCH2CH2CH3 + HBr CH3CH2Br +
CH3CH2CH2OH
DEHYDRATION OF ROH BY E1 ELIMINATION: REACTION OF THE C-O BOND
OXIDATION OF ROH: REACTION OF THE C-O AND O-H BONDS
ROH is oxidized to carbonyl compound.
EPOXIDES• Three-membered cyclic ethers, eg. Ethylene
oxide.• Can be prepared by reacting the alkenes with
peroxycarboxylic acid
B)Reactions of ethylene oxide
B) Epoxy Resins
- polymers with tremendous adhesive properties and are used to bind glass, porcelin, metal and wood
SULFUR ANALOGOUS TO ROH AND ROR
• Sulfur analogues of alcohols are called mercaptans, thiols or alkyl hydrogen sulfides
• Sulfur analogues of ethers are called thioeters or sulfides
• Thiols (RSH) – an alkane has been replace by SH
CH3CH2CH3 CH3CH2CH2SH
• Sulfides (RSR) – sulfur with two bonded alkyl groups
CH3CH2SCH2CH2CH3