Aromatic Aldehydes Ketones and Acids - Result Question 29
####36. Explain, why $o$-hydroxy benzaldehyde is a liquid at room temperature while $p$-hydroxy benzaldehyde is a high melting solid?
$(1999,2 M)$
Matching Type Questions
Answer Q. 22, Q. 23 and Q. 24 by appropriately matching the information given in the three columns of the following table. Column 1, 2 and 3 contain starting materials, reaction conditions, and type of reactions, respectively.
(2017 Adv.)
| Column 1 | Column 2 | Column 3 | |||
|---|---|---|---|---|---|
| (I) | Toluene | (i) | $NaOH / Br _2$ | (P) | Condensation |
| (II) | Acetophenone | (ii) | $Br _2 / h \nu$ | (Q) | Carboxylation |
| (III) | Benzaldehyde | (iii) | $\left(CH _3 CO\right) _2 O /$ $CH _3 COOK$ |
(R) | Substitution |
| (iv) | $NaOH / CO _2$ | (S) | Haloform | ||
| (IV) | Phenol |
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Solution:
- Intramolecular H-bonding in ortho hydroxy benzaldehyde is responsible for decrease in melting and boiling points.
Intramolecular H-bonding
p-hydroxy benzaldehyde molecules are associated by intermolecular $H$-bonding, has higher melting and boiling points.
