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