Chemistry [ 2 Marks Questions ]

Boiling points increase regularly as the molecular mass increases due to a corresponding increase in their Van der Waal's force of attraction. Among isomeric alcohols, 2° alcohols have lower boiling points than 1° alcohol due to a corresponding decrease in the extent of H-bonding because of steric hindrance. Thus the boiling point of Butan-2-ol is lower than that of Butan-1-ol. Overall increasing order of boiling points is, 2-methyl propane-2-ol < Butan-2-ol < Butan-1-ol.

2° alcohols have lower boiling points than 1° alcohol due to a corresponding decrease in the extent of H-bonding because of steric hindrance. Therefore Propan-1-ol has a higher boiling point than Propan-2-ol. Hydrogen group increases, boiling point also increases. Overall increasing order of boiling points is, propan-2-ol < Propan-1-ol < propan-1, 3-diol < propan-1, 2, 3-triol.

Acetaldehyde reacts with Grignard reagent to give an addition product, which further undergoes acid hydrolysis to yield secondary alcohol, that is isopropyl alcohol.

According to Saytzeff’s rule the dehydration of 3, 3-dimethyl butane-2-ol gives a mixture of alkenes. But the secondary carbocation formed in this reaction undergoes rearrangement to form a more stable tertiary carbocation which further, undergoes 13 elimination leads more stable product, that is 2, 3-dimethyl but-2-ene (more yield). According to Saytzeff’s rule, 2, 3-dimethyl pent-2-ene is the major product.

Conversion of benzyl alcohol into benzoic acid:

It is a special type of isomerism in which molecules with the same formula, same functional group, but different only in the nature of the alkyl group attached to oxygen.

On passing air to a mixture of cumene (isopropyl benzene) and 5% aqueous sodium carbonate solution, cumene hydro peroxide is formed by oxidation. It is treated with dilute acid to get phenol and acetone.

1. The reaction of phenol with aqueous sodium hydroxide solution indicates that phenol is a stronger acid than alcohols in water
.2. Because phenoxide ion formed is stabilised by resonance whereas alkoxide ion formed is destabilised by positive inductive effect of alkyl group.
3. Presence of electron withdrawing group such as nitro group enhances the acidic strength of phenol. lt is due to the effective delocalisation of the negative charge in phenoxide ion.

Ethanol undergoes intermolecular H-bonding due to the presence of a hydrogen atom attached to the electronegative oxygen atom. As a result, ethanol exists as associated molecules.


Consequently, a large amount of energy is required to break these hydrogen bonds. Therefore, the boiling point of ethanol is higher than that of methoxymethane which does not form H-bonds.

Alcohols can form H-bond with water molecules and break the H-bond already existing between the water molecules. Therefore, they are soluble in water.


On the other hand hydrocarbons do not have the ability to form H-bond with water molecules. Hence they are insoluble in water.

1. When ether bottle is kept open, they are exposed to atmospheric oxygen and slowly oxidised to form hydroperoxides and dialkyl peroxides. These are explosive in nature. Such a spontaneous oxidation by atmospheric oxygen is called autooxidation.

1. Oxygen of ether can also form Hydrogen bond with water and hence they are miscible with water.
2. Ethers dissolve wide range of polar and non-polar substances.

Methyl ethers can be prepared when ethanol is treated with diazomethane in presence of fluoro boric acid.

Phenol couples with benzene diazonium chloride in an alkaline solution to form p-hydroxy azobenzene(a red orange dye).

Phenol couples with benzene diazonium chloride in an alkaline solution to form p-hydroxy azobenzene(a red orange dye).

O-nitro phenol is slightly soluble in water and more volatile due to intra molecular hydrogen bonding, whereas P-nitro phenol is more soluble in water and less volatile due to intermolecular hydrogen bonding.