The carbon-oxygen bond in phenol is slightly stronger than that in methanol. Why ?
Positive resonance effect is observed in phenols. Due to this $+R$ effect, lone pair of electrons of $-$OH group are in conjugation with $\pi$ electrons of the ring and the following resonance hybrid are obtained.
From the above resonating structure, it is very clear that $\mathrm{C}-\mathrm{O}$ bond of phenol acquires some partial double bond character while the $\mathrm{C}-\mathrm{O}$ bond of methanol is purely single bond. Therefore, the carbon-oxygen bond in phenol is slightly stronger than that in methanol.
Arrange water, ethanol and phenol in increasing order of acidity and give reason for your answer.
The phenoxide ion obtained after the removal of a proton is resonance stabilised as follows
Whereas, the ethoxide ion obtained after the removal of a proton is not stabilised but destabilised due to $+I$ effect of $-\mathrm{C}_2 \mathrm{H}_5$ group. Therefore, phenol is a stronger acid than ethanol. $+I$ effect of $\mathrm{CH}_3-\mathrm{CH}_2$ group increase the electron density on $\mathrm{O}-\mathrm{H}$ bond in ethanol. As the electron density on the O - H bond of ethanol is more than that of water. So, ethanol is a weaker acid than water. Thus, the increasing order of acidity is
ethanol < water < phenol
Match the structures of the compounds given in Column I with the name of the compounds given in Column II.
| Column I | Column II | ||
|---|---|---|---|
| A. |  |
1. | Hydroquinone |
| B. |  |
2. | Phenetole |
| C. |  |
3. | Catechol |
| D. |  |
4. | o-cresol |
| E. |  |
5. | Quinone |
| F. |  |
6. | Resorcinol |
| 7. | Anisole |
A. $\rightarrow(4)$ B. $\rightarrow$ (3) C. $\rightarrow(6)$ D. $\rightarrow$ (1) E. $\rightarrow$ (7) F. $\rightarrow$ (2)
A. Cresols are organic compounds which are methyl phenols. There are three forms of cresol-o-cresol, $p$-cresol and $m$-cresol.
B. Catechol is also known as pyrocatechol. Its IUPAC name is 1,2-dihydrobenzene. It is used in the production of pesticides, perfumes and pharmaceuticals.
C. Its IUPAC name is 1,3-dihydroxybenzene. Resorcinol is used to treat acne, seborrheic dermatitis and other skin disorder.
D. Hydroquinone is also known as quinol. Its IUPAC name is 1, 4- dihydroxybenzene. It is a white granular solid. It is a good reducing agent.
E. Anisole or methoxy benzene, is a colourless liquid with a smell reminiscent of anise seed.
F. Phenetole is an organic compound. It is also known as ethylphenyl ether. It is volatile in nature and its vapours are explosive in nature.
Match the starting material given in Column I with the products formed by these (Column II) in the reaction with HI.
| Column I | Column II | ||
|---|---|---|---|
| A. |  |
1. |  |
| B. |  |
2. |  |
| C. |  |
3. |  |
| D. |  |
4. |  |
| 5. |  |
||
| 6. |  |
||
| 7. |  |
||
A. $\rightarrow(4)$ B. $\rightarrow(5)$ C. $\rightarrow$ (2) D. $\rightarrow$ (1)
A. $\mathrm{CH}_3-\mathrm{O}-\mathrm{CH}_3$ is a symmetrical ether so the products are $\mathrm{CH}_3 \mathrm{I}$ and $\mathrm{CH}_3 \mathrm{OH}$.
B. $\operatorname{In}\left(\mathrm{CH}_3\right)_2 \mathrm{CH}-\mathrm{O}-\mathrm{CH}_3$ unsymmetrical ether, one alkyl group is primary while another is secondary. So, it follows $\mathrm{S}_{\mathrm{N}}{ }^2$ mechanism. Thus, the halide ion attacks the smaller alkyl group and the products are
C. In this case, one of the alkyl group is tertiary and the other is primary. It follows $S_N{ }^1$ mechanism and halide ion attacks the tertiary alkyl group and the products are $\left(\mathrm{CH}_3\right)_3 \mathrm{C}-\mathrm{I}$ and $\mathrm{CH}_3 \mathrm{OH}$.
D. Here, the unsymmetrical ether is alkyl aryl ether. In this ether $\mathrm{O}-\mathrm{CH}_3$ bond is weaker than $\mathrm{O}-\mathrm{C}_6 \mathrm{H}_5$ bond which has partial double bond character due to resonance. So, the halide ion attacks on alkyl group and the products are $\mathrm{C}_6 \mathrm{H}_5-\mathrm{OH}$ and $\mathrm{CH}_3 \mathrm{I}$.
Match the items of Column I with items of Column II.
| Column I | Column II | ||
|---|---|---|---|
| A. | Antifreeze used in car engine | 1. | Neutral ferric chloride |
| B. | Solvent used in perfumes | 2. | Glycerol |
| C. | Starting material for picric acid | 3. | Methanol |
| D. | Wood spirit | 4. | Phenol |
| E. | Reagent used for detection of phenolic group | 5. | Ethylene glycol |
| F. | By product of soap industry used in cosmetics | 6. | Ethanol |
A. $\rightarrow(5)$ B. $\rightarrow(6)$ C. $\rightarrow(4)$ D. $\rightarrow(3)$ E. $\rightarrow$ (1) F. $\rightarrow$ (2)
A. IUPAC name of ethylene glycol is ethane $-1,2$ - diol. It is primarily used as raw material in the manufacturing of polyester fibers and fabric industry. A small percentage of it is used in antifreeze formulations.
B. Ethanol is a good solvent for fatty and waxy substances. Fats and waxes provide odour to the perfumes. Apart from being a good solvent, it is less irritating to the skin. So, it is used in perfumes.
C. Phenol is converted into picric acid (2, 4, 6-trinitro-phenol) by the reaction of phenol with conc. $\mathrm{HNO}_3$.
D. Methanol, $\mathrm{CH}_3 \mathrm{OH}$ is also known as 'wood spirit' as it was produced by the destructive distillation of wood.
E. Neutral ferric chloride give purple/red colour when treated with phenols. It is the reagent used for detection of phenolic group.
F. Soaps are prepared by the reactions of fatty acid with NaOH .
This glycerol (propan-1,2,3-triol) is the by product of soap industry and used in cosmetics.