The correct order in aqueous medium of basic strength in case of methyl substituted amines is :
- $NH _3> Me _3 N > MeNH _2> Me _2 NH$
- $Me _2 NH > Me _3 N > MeNH _2> NH _3$
- $Me _2 NH > MeNH _2> Me _3 N > NH _3$
- $Me _3 N > Me _2 NH > MeNH _2> NH _3$
The Correct Option is C
Solution and Explanation
In aqueous medium, the basic strength of amines depends on:
1. Electron density on the nitrogen atom (due to inductive effect of methyl groups).
2. Solvation effect, which stabilizes the conjugate acid after accepting a proton.
- Dimethylamine (Me$_2$NH): The best combination of inductive effect and solvation, making it the most basic.
- Methylamine (MeNH$_2$): Slightly less basic due to less inductive effect but better solvation.
- Trimethylamine (Me$_3$N): Weaker basicity because bulky groups hinder solvation.
- Ammonia (NH$_3$): Lowest basicity due to the absence of inductive effect.
Thus, the basic strength order is Me$_2$NH $>$ MeNH$_2$ $>$ Me$_3$N $>$ NH$_3$. Basicity in aqueous medium is influenced by both inductive effects and solvation. Dimethylamine balances these effects best, while trimethylamine suffers from steric hindrance.
Top Questions on Amines
Amines are usually formed from amides, imides, halides, nitro compounds, etc. They exhibit hydrogen bonding which influences their physical properties. In alkyl amines, a combination of electron releasing, steric and H-bonding factors influence the stability of the substituted ammonium cations in protic polar solvents and thus affect the basic nature of amines. Alkyl amines are found to be stronger bases than ammonia. Amines being basic in nature, react with acids to form salts. Aryldiazonium salts, undergo replacement of the diazonium group with a variety of nucleophiles to produce aryl halides, cyanides, phenols and arenes.
How can you convert the following:
(i) Ethanoic acid to methanamineAmines are usually formed from amides, imides, halides, nitro compounds, etc. They exhibit hydrogen bonding which influences their physical properties. In alkyl amines, a combination of electron releasing, steric and H-bonding factors influence the stability of the substituted ammonium cations in protic polar solvents and thus affect the basic nature of amines. Alkyl amines are found to be stronger bases than ammonia. Amines being basic in nature, react with acids to form salts. Aryldiazonium salts, undergo replacement of the diazonium group with a variety of nucleophiles to produce aryl halides, cyanides, phenols and arenes.
Arrange the following in increasing order of their basic strength in aqueous solution:
CH$_3$–NH$_2$, (CH$_3$)$_2$NH, (CH$_3$)$_3$NAmines are usually formed from amides, imides, halides, nitro compounds, etc. They exhibit hydrogen bonding which influences their physical properties. In alkyl amines, a combination of electron releasing, steric and H-bonding factors influence the stability of the substituted ammonium cations in protic polar solvents and thus affect the basic nature of amines. Alkyl amines are found to be stronger bases than ammonia. Amines being basic in nature, react with acids to form salts. Aryldiazonium salts, undergo replacement of the diazonium group with a variety of nucleophiles to produce aryl halides, cyanides, phenols and arenes.
Why is the pK$_b$ value of aniline more than that of methylamine?- How can you obtain the following?
(a) Aniline from ammonium benzoate
(b) Benzene diazonium chloride from nitrobenzene
(c) 2,4,6-Tribromoaniline from aniline - An amine 'X' reacts with Hinsberg reagent and the product obtained is soluble in alkali. The amine 'X' is:
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Concepts Used:
Amines
Amine is a type of compound which is derived from ammonia (NH3). According to Organic chemistry, they are basically classified as the functional groups of the organic nitrogen compounds that contain nitrogen atoms with a lone pair.
Amine - Types
Primary Amines:
It is formed when one hydrogen atom in ammonia is substituted by an alkyl or aromatic group. Amino acids and methyl amine are the best examples that why aromatic amines include aniline.
Secondary Amines:
Amines that have two organic substitutes either alkyl or aryl ones or both and are bound to the nitrogen together with one hydrogen are termed as secondary amines. For Example, Dimethylamine.
Tertiary Amines:
Tertiary Amines are the amines where the nitrogen consists of three organic substitutes. For example, Trimethylamine and EDTA.