question_answer 49)

  Which of the following should be most volatile? (I)       (II) (III)            (IV) (a) II                                       (b) IV (c) I                                        (d) III

Answer:

                  (b) 1° and 2° Amines due to intermolecular H-bonding have higher boiling points (and hence less volatile than 3° amines and hydrocarbons of comparable molecular mass. Further, due to polar C-N bonds, 3° amines are more polar than hydrocarbons which are almost non-polar. Therefore, due to weak dipole- dipole interactions, 3° amines have higher boiling point (i.e., less volatile) than hydrocarbons. In other words, has the least b.p. and hence is most volatile.