Explain order of Kb in aquas solution of Triethylamine, Diethylamine and Ethylamine.

(Et)₂NH     >     (Et)₃N     >      (Et)NH₃             {Et = Ethyl group (-CH₂CH₃)}

Answer:-

-> (Et)₂NH is more basic than (Et)₃N because of less steric hindrance and more hydration energy of (Et)₂NH.

-> (Et)₃N is more basic than (Et)NH₃ because of more +I Effect in (Et)₃N.

Why Dimethylamine (2' amonia) is more basic than Trimethylamine (3' amonia) ?

Answer:-

-> Less steric hindrance in (CH₃)₂NH than (CH₃)₃N.

-> More hydration energy of (CH₃)₂NH than (CH₃)₃N.


Example:
  
Order of basic strength:

(CH₃)₂-NH           >           (CH₃)-NH₂            >        (CH₃)₃-N

{Secondary amine}       {Primary amine}            {Tertiary amine}

*Basic strength depends on:-

                                                  -> Inductive effect

                                                  -> Steric hindrance

                                                  -> Hydration energy

So, Dimethylamine is more basic than Trimethylamine in aqueous solution.

Reason:-

a. Less steric hindrance of Dimethylamine than Trimethylamine.

b. More hydration energy of Dimethylamine than Trimethylamine.

Which of the following have maximum PKa value ?

Options:

a. CH₃-CF-COOH                                                 b.  F-CH₂-CH₂-COOH

c. CH₃-CHBr-COOH                                             d.  CH₂Br-CH₂-COOH

Answer: (d)

Reason:

              Minimum –I Effect

              Minimum acidic strength

              Minimum K^a

              Maximum P^ka

which of the following is most reactive towards NAR ? [AIPMT 2006]

 

Answer:

 d)

 

 Explanation: 

 Minimum +I effect

So, More +ve charge on C-atom

So, More reactive.

Reactivity order:

d  > c  >  b  >  a

which of the following easily gives white ppt of AgCl with silver nitrate?

Question:-

Which of the following easily gives white ppt of  AgCl  with silver nitrate?

 

Option:-

a.  CH₃—Cl 

b.  CH₃—CH₂—Cl

c.  (CH₃)₂C—Cl

d.  (CH₃)₃C—Cl

 

Answer:-  (d)

 

Explanation:-

Their Carbocation and stability order:-

a.      CH₃⁺       <    b.  CH₃—C⁺H₂   <    c.  (CH₃)₂C⁺   <    d.  (CH₃)₃C⁺

a.      Methyl carbocation  <  b. 1’C  <  c. 2’ C  <  d. 3’C

So reactivity order:-

a.      CH₃—Cl    <   b.  CH₃—CH₂—Cl   <   c.  (CH₃)₂C—Cl   <   d.  (CH₃)₃C—Cl