CHAPTER 11 (ALCOHOLS, PHENOLS AND ETHERS ) · 2018-11-23 · CHAPTER – 11 (ALCOHOLS, PHENOLS AND...

CHAPTER – 11 (ALCOHOLS, PHENOLS AND ETHERS )

IMPORTANT TOPICS

COMMON NAMES IUPAC NAMES CH3OH Methyl alcohol Methanol CH3CH2OH Ethyl alcohol Ethanol CH3CH(OH) CH3 Isopropyl alcohol Propan-2-ol CH3OCH3 Dimethyl ether Methoxymethane C2H5OC2H5 Diethyl ether Ethoxyethane CH3OCH2CH2CH3 Methyl n-propyl ether 1-Methoxypropane C6H5OCH3 Methyl phenyl ether Methoxybenzene C6H5OCH2CH3 Ethyl phenyl ether Ethoxybenzene C6H5O(CH2)6 – CH3 Heptyl phenyl ether 1-Phenoxyheptane Physical properties

Boiling points: Boiling points of alcohols and phenols are higher in comparison to other classes of compounds,

namely hydrocarbons, ethers, haloalkanes and haloarenes of comparable molecular masses. This is because the –OH group in alcohols and phenols is involved in intermolecular H-bonding

The boiling points of alcohols and phenols increase with increase in the number of carbon atoms. This is because of increase in van der Waals forces with increase in surface area. In alcohols, the boiling points decrease with increase of branching in carbon chain. This is because of decrease in van der Waals forces with decrease in surface area.

Solubility: Solubility of alcohols and phenols in water is due to their ability to form hydrogen bonds with

water molecules. The solubility of alcohols decreases with increase in size of alkyl/aryl (hydrophobic) group

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CHEMICAL PROPERTIES

1.REACTION WITH METALS

2.ESTERIFICATION

3.Reaction with hydrogen halides:

conc.HCl ZnCl2

ROH + HX RX + H 2 OLucas reagent

4.Reaction with phosphorus trihalides:

3 ROH + PX 3 → 3 R-X + H 3 PO 3 (X = Cl, Br)

5.Dehydration:





Step 1: Formation of protonated alcohol.

Step 2: Formation of carbocation: It is the slowest step and hence, the rate determining step of the reaction.

Step 3: Formation of ethene by elimination of a proton.

6.Oxidation

Cu,573K or

CrO3 or

PCC Primary alcohol Aldehyde

Cu,573K or

CrO3 Secondary alcohol Ketone

Cu,573K

or KMnO4

Tertiary alcohol Alkene

Acidified potassium permanganate Alcohol Carboxylic acid





Acidic nature:

Phenol > H 2 O > Primary alcohol > Secondary alcohol > Tertiary

Alcoho Phenol is more acidic than alcohol because:

The ionisation of an alcohol and a phenol takes place as follows:

After the loss of proton the phenoxide undergoes resonance stabilization, but alcohol does not undergoes resonance stabilization

PROPERTIES OF PHENOL:





Reimer Tiemann Reaction: In this reaction, salicyaldehyde(2-Hydroxy benzaldehyde) is prepared on reaction of phenols with chloroform while salicylic acid(2-Hydroxy benzoic acid) is formed when phenols are treated with carbon tetrachloride

Kolbe’s Reaction: In this reaction , salicylic acid is prepared by the reaction of sodium phenoxide with carbon dioxide followed by acidification.

PROPERTIES OF AROMATIC ETHERS(ANISOLE)





How to distinguish between some important pair of organic

compounds:

a. Phenol and alcohol:

Phenol on reaction with neutral FeCl 3 gives purple colour whereas alcohols do not give purple colour.

6 C 6 H 5 OH + Fe 3+ → [Fe(OC 6 H 5 ) 6 ] 3- + 6 H +

Purple colour

b. Primary, secondary and tertiary alcohol: Lucas reagent test:

conc.HCl ZnCl2

ROH + HCl RCl + H 2 O(Lucas reagent)

If it is a primary alcohol, no turbidity appears at room temperature. Turbidity appears only on heating. If it is a secondary alcohol, turbidity appears in 5 minutes. If it is a tertiary alcohol, turbidity appears immediately.

c. Methanol and ethanol: Iodoform test:

Ethanol when reacted with (I 2 and NaOH) or NaOI gives yellow ppt of

iodoform since it has the presence of CH 3 -CH (OH)- group. But methanol does not give this

test

C 2 H 5 OH +4I2+6NaOH CHI 3 + 5NaI + 5H 2 O + HCOONa

Yellow ppt





CHAPTER 11 (ALCOHOLS, PHENOLS AND ETHERS ) · 2018-11-23 · CHAPTER – 11 (ALCOHOLS, PHENOLS AND...

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