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प्रश्न
Give a plausible explanation for the following:
Why do primary amines have higher boiling points than tertiary amines?
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उत्तर
In a molecule of tertiary amine, there are no H-atoms whereas in primary amines, two hydrogen atoms are present. Due to the presence of H-atoms, primary amines undergo extensive intermolecular H-bonding. As a result, extra energy is required to separate the molecules of primary amines. Hence, primary amines have higher boiling points than tertiary amines.
\[\begin{array}{cc}
\ce{H}\phantom{.............}\ce{H}\phantom{............}\ce{H}\phantom{....}\\
\phantom{...}|\phantom{..............}|\phantom{.............}|\phantom{.......}\\
\ce{\text{- - - - - -} N-H \text{- - - - - -} N-H \text{- - - - - -} N-H \text{- - - - - -}}\\
\phantom{...}|\phantom{..............}|\phantom{.............}|\phantom{.......}\\
\ce{\underset{Primary Amine}{R\phantom{.............}R\phantom{............}R\phantom{....}}}
\end{array}\]
\[\begin{array}{cc}
\ce{R}\phantom{....}\\
|\phantom{....}\\
\ce{N-R}\\
|\phantom{....}\\
\ce{\underset{Tertiary amine}{R}}\phantom{....}
\end{array}\]
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संबंधित प्रश्न
What is the action of nitrous acid on primary nitroalkane?
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Arrange the following in the increasing order of their boiling points:
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Reason (R): Tertiary amines have three alkyl groups which cause +I effect.
Select the most appropriate answer from the options given below:
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Match List I with List II.
| List I | List II | ||
| (A) | Benzenesulphonyl chloride | (I) | Test for primary amines |
| (B) | Hoffmann bromamide reaction | (II) | Anti Saytzeff |
| (C) | Carbylamine reaction | (III) | Hinsberg reagent |
| (D) | Hoffmann orientation | (IV) | Known reaction of Isocyanates |
Choose the correct answer from the options given below:
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Explain why (CH3)2NH is more basic than (CH3)3N in aqueous solution.
Among dimethylamine (pKb = 3.27) and diethylamine (pKb = 3.0), which one is more basic?
