Resonance structures of propenal are given below. Which of these resonating structures is more stable? Give reason for your answer.
The structure having more covalent bonds in a resonating structure, has more stability. Further, there is charge separation in structure (II) and the terminal carbon has only a sextet of electrons in (II). These two factors makes structure (II) less stable.
Hence, I > II in terms of stability.
By mistake, an alcohol (boiling point $97^{\circ} \mathrm{C}$ ) was mixed with a hydrocarbon (boiling point $68^{\circ} \mathrm{C}$ ). Suggest a suitable method to separate the two compounds. Explain the reason for your choice.
The difference in boiling point of two liquids is more than $20^{\circ} \mathrm{C}$. Hence, simple distillation can be used and since at the boiling point of low boiling liquid, the vapours would consist entirely of only low boiling liquid without any contamination of vapours of high boiling liquid and vice-versa. Thus, both the liquids can be distilled without any decomposition.
Which of the two structures $(A)$ and $(B)$ given below is more stabilised by resonance.
Explain $$\mathop {C{H_3}COOH}\limits_{(A)} $$ and $$\mathop {C{H_3}CO{O^\Theta }}\limits_{(B)} $$
Resonating structures of (A) and (B) are as follows
Structure (II) is less stable than structure (I) because later carries separation of positive and negative charges. Therefore, contribution of structure (II) is less than that of (I) towards the resonance hybrid of compound (A), i.e., $\mathrm{CH}_3 \mathrm{COOH}$. On contrary, structure (III) and (IV) are of equal energy and hence contribute equally towards the resonance hybrid of compound ( $B$ ). Therefore, structure $(B)$ is more stable than structure $(A)$ i.e., $\mathrm{CH}_3 \mathrm{COO}^{\ominus}$.
Match the type of mixture of compounds in Column I with the technique of separation/purification given in column II.
| Column I | Column II | ||
|---|---|---|---|
| A. | Two solids which have different solubilities in a solvent and which do not undergo reaction when dissolved in it | 1. | Steam distillation |
| B. | Liquid that decomposes at its boiling point | 2. | Fractional distillation |
| C. | Steam volatile liquid | 3. | Simple distillation |
| D. | Two liquids which have boiling points close to each other | 4. | Distillation under reduced pressure |
| E. | Two liquids with large difference in boiling points. | 5. | Crystallisation |
| Column I | Column II | ||
|---|---|---|---|
| A. | Two solids which have different solubilities in a solvent and which do not undergo reaction when dissolved in it | 1. | Crystallisation |
| B. | Liquid that decomposes at its boiling point | 2. | Distillation under reduced pressure |
| C. | Steam volatile liquid | 3. | Steam distillation |
| D. | Two liquids which have boiling points close to each other | 4. | Fractional distillation |
| E. | Two liquids with large difference in boiling points. | 5. | Simple distillation |
Match the terms mentioned in Column I with the terms in Column II.
| Column I | Column II | ||
|---|---|---|---|
| A. | Carbocation | 1. | Cyclohexane and 1-hexene |
| B. | Nucleophile | 2. | Conjugation of electrons of C-H$$\sigma$$ bond with empty p-orbital present at adjacent positively charged carbon |
| C. | Hyperconjugation | 3. | sp$$^2$$ hybridised carbon with empty p-orbital |
| D. | Isomers | 4. | Ethyne |
| E. | sp-hybridisatioin | 5. | Species that can receive a pair of electrons |
| F. | Electrophile | 6. | Species that can supply a pair of electrons |
A - 3, B - 6, C - 2, D - 1, E - 4, F - 5
| Column I | Column II | Explanation | |
|---|---|---|---|
| A. | Carbocation | sp$$^2$$-hybridised carbon with empty p-orbital | H$$_3$$C$$^+$$ is carbocation. Loss of e$$^-$$ makes its p-orbitals empty (sp$$^2$$-hybridised carbon) |
| B. | Nucleophile | Species that can supply a pair of electron | Nucleus loving i.e., having negative charge or excess of electrons |
| C. | Hyperconjugation | Conjugation of electrons of $\mathrm{C}-\mathrm{H} \sigma$ bond with empty $p$-orbital present at adjacent positively charged carbon | |
| D. | Isomers | Cyclohexane and 1-hexene | Same molecular formula but different structures |
| E. | sp-hybridisatioin | Ethyne | HC = CH (sp-hybridisation) |
| F. | Electrophile | Species that receive a pair of electron | Electron loving i.e., positive charge or lack of electrons |