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प्रश्न
Explain why (CH3)2NH is more basic than (CH3)3N in aqueous solution.
उत्तर
The substituted ammonium cation is stabilised in the aqueous state not only by the alkyl group (+I), which releases electrons but also by solvation with water molecules. Less solvation will occur and the ion will be less stabilised as its size increases. Ions are stable in the following order:
| \[\begin{array}{cc} \ce{OH2}\phantom{.....}\\ \ce{⫶}\phantom{........}\\ \ce{H}\phantom{........}\\ |\phantom{........}\\ \ce{R-N^+-N...OH2}\\ |\phantom{........}\\ \ce{H}\phantom{........}\\ \ce{⫶}\phantom{........}\\ \ce{OH2}\phantom{.....} \end{array}\] |
> | \[\begin{array}{cc} \phantom{......}\ce{R}\phantom{....}\ce{H...OH2}\phantom{}\\ \phantom{}\backslash\phantom{..}/\phantom{}\\ \ce{\overset{⊕}{N}}\\ \phantom{}/\phantom{..}\backslash\phantom{}\\ \phantom{......}\ce{R}\phantom{....}\ce{H...OH2}\phantom{} \end{array}\] |
> | \[\begin{array}{cc} \ce{R}\phantom{............}\\ \backslash\phantom{..........}\\ \ce{R - \overset{+}{N}-H...OH2}\\ /\phantom{.........}\\ \ce{R}\phantom{............} \end{array}\] |
The stronger the matching amine as a base, the more stable the substituted \[\ce{\overset{+}{N}H4}\] cation.
Thus the order of basicity, Primary > Secondary > Tertiary.
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संबंधित प्रश्न
How are 1 - nitropropane, 2-nitropropane and 2-methyl 2- nitropropane are distinguished from each other using nitrous acid?
Give plausible explanation for each of the following:
Why do primary amines have higher boiling point than tertiary amines?
What is the action of nitrous acid on tertiary nitroalkane
Given below are two statements labelled as Assertion (A) and Reason (R).
Assertion (A): Tertiary amines are more basic than corresponding secondary and primary amines in gaseous state.
Reason (R): Tertiary amines have three alkyl groups which cause +I effect.
Select the most appropriate answer from the options given below:
Compound A is converted to B on reaction with CHCl3 and KOH. The compound B is toxic and can be decomposed by C. A, B and C respectively are ______.
Isocyanide reaction involves the intermediate formation of ______.
The presence of primary amines can be confirmed by ______.
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:
Carbylamine test is the distinguishing test for ______.
Among dimethylamine (pKb = 3.27) and diethylamine (pKb = 3.0), which one is more basic?
