question_answer

  (a) Account for the following : (i) Electrophilic substitution in benzoic acid takes place at meta position.                                                                1 (ii) Carboxylic acids have higher boiling points than alcohols of comparable molecular mass.                         1 (b) How will you bring about the following conversions: (i) Propanone to propene,                                                                                                                                           1 (ii) Benzoic acid to benzaldehyde,                                                                                                                                            1 (iii) Ethenol to 3-hydroxybutenal ?                                                                                                                                           1

Answer:

  (a) (i) It is because there is +ve charge on o- and p-position, therefore, electrophilic substitution take place at m-position as shown in the following resonating structures.                                                    1     (ii) Carboxylic acids have higher boiling points than alcohols because they operate hydrogen bonding among their molecules. Hydrogen bonding among acid molecules is far stronger than among alcohol molecules.                                                 (b) (i) Propanone to propene:                                                                                 1 (ii) Benzoic acid to benzaldehyde:                                               1           (iii) Ethanol to 3-hydroxybutanal:                                                                 1