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Arrange the following compounds in increasing order of their boiling points : CH_(3)CHO, CH_(3)CH_(2)OH, CH_(3)OCH_(3), CH_(3)CH_(2)CH_(3) |
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Answer» Solution :The molecular masses of all these compounds are comparable : `CH_(3)CHO(4), CH_(3)CH_(2)OH(46), CH_(3)COCH_(3)(46),CH_(3)CH_(2)CH_(3)(44). CH_(3)CH_(2)OH`displayes extensiveintermolecular H - bonding. Therefore, it exists as an ASSOCIATED molecule molecule and hence its BOILING point is the highest (351K). `CH_(3)CCHO` has a higher VALUE of dipole moment (2.72 D) than `CH_(3)OCH_(3)` (1.18 D). Therefore, dipole - dipole interactions are stronger in `CH_(3)CHO` than in `CH_(3)OCH_(3)` and hence the boiling point of `CH_2CHO` is much higher thant that of `CH_3OCH_3.CH_3CH_3CH_3` shows only weak van der Walls.s fores. `CH_3OCH_3` has some dipole -dipole interactions and hence the boiling point of `CH_3OCH_3` is higher than that of `CH_3CH_2CH_3` . Thus, the increasing order of boiling points of the compounds is : `CH_3CH_2CH_3 < CH_3OCH_3 < CH_3CHO < CH_3CH_2OH`. |
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