Chemistry

11.70

Oxidation of propane-1-ol with alkaline KMnO₄ solution gives propanoic acid as the product. As the oxidation of primary alcohol gives carboxylic acid as the major product in the presence of a strong oxidizing reagent. And here KMnO₄ is a very strong oxidizing agent.

A mixture of o-bromo phenol and p-bromo phenol is formed.

The formation of 2 products depends totally on the reaction conditions.

Dilute HNO₃ with phenol.

Only dilute acid will be required for the nitration of phenol, nitric acid contains a small amount of nitrous acid which because of the activation of the ring will be more than enough to nitrate the phenol. Two products are formed 2-nitrophenol (ortho) and 4-nitrophenol (para).

Treating Phenol with chloroform in presence of aqueous NaOH results in the formation of salicylaldehyde (Reimer-Tiemann reaction)

11.68

Ortho-nitro phenol is more acidic than ortho-methoxy phenol.

Explanation: Due to strong –R and –I effect of NO₂ group, electron density in the O-H bond decreases and hence the loss of a proton becomes easy.

Now after the loss of a proton, the o-nitrophenoxide ion left behind is stabilized by resonance and thus making o-nitro phenol a stronger acid.

In contrast, due to the +R effect of methoxy group increases the electron density in the O-H bond. Thereby making the loss of proton difficult.

Now, the o-methoxyphenoxide ion left after the loss of a proton is destabilized by resonance. The two negative charges repel each other, thereby destabilizing the o-methoxyphenoxide ion.

Therefore, o-nitrophenol is more acidic than o-methoxyphenyl.

11.67

The acidic nature of phenol can be represented by the following two reactions:-

(a) Phenols react with sodium to give sodium phenoxide, liberating H₂.

(b) Phenols react with sodium hydroxide to give sodium phenoxide and water as a by-product.

The acidity of phenol is more than that of ethanol. This is because phenol after losing a proton becomes phenoxide ion which undergoes resonance and is stabilized whereas ethoxide ion does not.

The resonating structures of phenoxide ion are shown as below:

The lone pair of electrons on oxygen delocalizes into the benzene (mesomeric effect) which reduces the electron density in the O-H bond. The O-H bonds are weaker and therefore breaks easily whereas in ethanol the electron releasing inductive effect of the alkyl group increases the electron density on the O-H bond. This strengthens the bond so the bond does not break easily. Therefore making ethanol less acidic than phenol.

11.66 

1. 1-phenylethanol from a suitable  - The addition of water takes place according to Markovnikov rule. The alkene taken is styrene. And According to the rule, the positive charge i.e. H⁺ goes to the carbon of the double bond which has more number of hydrogens and the negative part i.e. OH- goes to the carbon that has less number of hydrogens. Therefore resulting the final product as 1-phenyl ethanol.

2. In the above conversion, NaOH gets dissociated into Na⁺ and OH^-and Na⁺ then combines with Cl of chloromethylcyclohexane forming NaCl and thus the final product Cyclohexylmethanol is obtained.

3. In this conversion also, Na forms the compound with Cl i.e. NaCl and to compensate the negative charge formed by Cl, OH attacks at that position resulting in pentan-1-ol.