Test Level 1: Previous Year Questions - Organic Chemistry - JEE MCQ

As the branching increases so the portion tendency of CH₃ group increases and therefore the order of inductive effect increases with increase in branching and so the option a is correct.

The correct answer is option B.

After introducing it to a benzene ring:

The order of inductive effect is:

+I order: 3o  > 2o  > Methyl 
Reason: More number of α hydrogens.

Except the amines containing tertiary butyl group, all lower aliphatic amines are stronger bases than ammonia because of +I (inductive) effect. The alkyl groups, which are electron releasing groups, increase the electron density around the nitrogen thereby, increasing the availability of the lone pair of electrons to proton or Lewis acids and making the amine more basic.

The observed order in the case of lower members is found to be as secondary > primary > tertiary. This anomalous behavior of tertiary amines is due to steric factors i.e. crowding of alkyl groups cover nitrogen atom from all sides and thus makes it unable for protonation. Thus the relative strength is in order (CH₃)₂NH > CH₃NH₂ > NH₃.

The correct answer is option A
For the reaction to be faster the Z should be a weak nucleophile and better leaving group. Weaker bases are good leaving groups.
In the given options, Cl⁻ is the weakest conjugate base of strong acid HCl and thus will be removed by nucleophile at the fastest rate.
CH₃​COO⁻,C₂​H_5​O− and NH²⁻​ are strong conjugate bases of weak acids and therefore have weak leaving tendencies.

For o-NO₂C₆H₄COOH, -M effect and –I effect of –NO₂ both acts (as –NO₂ is closest to acid). M
Meta position, there is no –M effect of –NO₂ only –I effect. 
Para position –M effect of –NO₂ acts but –I don’t (Para position is far from acid)  
Since –NO₂ is an electron-withdrawing group, it will withdraw electrons from –COOH which will release H⁺ to gain the electron. 
Therefore, the answer is d

In all 3 cases N lone pair are in resonance... and hence cannot be donated! but in 4th one N lone pair are not participating in resonance.  So it can be easily donated.  Therefore its basicity is strongest.

The correct answer is option D
Conjugate base (nucleophile) is strong if acid is weak and vice-versa.
A) CH₃O∣∣C−O− is a conjugate base of CH₃O∣∣C−OH (I).
B) CH₃O− is a conjugate base of CH₃OH (II).
C) CN− is a conjugate base of HCN (III).
D) p−H₃C−C₆H₄−SO₂−O− is conjugate base of p−H₃C−C₆H₄−SO₂−OH(IV).
Order of acidic nature is IV>I>III>II.
Hence, the decreasing order of nucleophilicity is B>C>A>D.

For the reaction to be faster the Z should be weak nucleophile and better leaving group. Weaker base are good leaving groups.
In the given options, Cl^- is the weakest conjugate base of strong acid HCl and thus will be removed by nucleophile at the fastest rate.
CH₃COO- ,C₂H₅O- and NH2- are strong conjugate base of weak acids and therefore have weak leaving tendency.

In aniline and in para nitro aniline lone pair of electrons are involved in delocalisation with the benzene ring and loses their basic nature. Acetanilide has electron withdrawing carbonyl group and so less basic in Benzylamine the lone pairs are readily available and hence strongly basic.

H₃C – CHBr – OCH₃

Methyl vinyl ether is a very reactive gas. It is hydrolysed rapidly by dilute acids at room temperature to give methanol and aldehyde. However, under anhydrous conditions at room temperature, it undergoes many addition reactions at the double bond.

Electrophilic addition reaction more favourable.

The correct answer is option D
CH₃​Br + Nu⁻ → CH₃​ − Nu + Br⁻
Making conjugate bases of all :
i) PHOH → H⁺ + PHO⁻
  Acid                    Base
   (Weak)         (Strong)
ii) A_c​OH → H⁺+ Ac​O⁻
    Acid                Base
  (Weak)          (Strong)
iii) H₂​O → H₊ + OH⁻
  Acid                Base
(Weak)            (Strong)
iv) CH₃​CH₂​OH → H⁺+ CH₃​CH₂​O⁻
Acid                      Base
 (Weakest)        (Strongest)
All alcohols are weaker acids than H_2​O.

The correct answer is option A
a.CH3​ − COOH, b.CH3​O − CH2 ​− COOH c.CF3​COOH d.(CH3​)2​CH−COOH
In the given compounds the common group is C − COOH

Here the +I group is −CH_3​
and −I groups are MeO− and F−
There are three F in the compound d, hence it is the most acidic compound.
The correct order is  d<a<b<c

The increasing order of basicity of the given compounds is (CH₃)2NH > CH₃NH2 > (CH₃)3N > C₆H₅NH₂. Due to the +I effect of alkyl groups, the electron density on nitrogen increases and thus the availability of the lone pair of electrons to proton increases and hence the basicity of amines also increases.

So aliphatic amines are more basic than aniline. In case of tertiary anine (CH₃)3N, the covering of alkyl groups over nitrogen atom from all sides makes the approach and bonding by a proton relatively difficult (steric hinderance), hence the basicity decreases. Electron withdrawing (C₆H₅–) groups decreases electron density on nitrogen atom and thereby decreasing basicity.

The correct option is C.

From the resonating structures of nitrobenzene, it can be seen that the nitro-group withdraws electrons from the ring and hence it deactivates the benzene ring for further electrophilic substitution.

1. (CH₃​)₃​C− is the least stable as it supply more electrons +I to the carbanion.

2. (CH₃​)₂​HC− is stable than (CH₃​)₃​C− as it has less +I effect compared to the other. But still it is less stable than the others, the reason being the same as above.

3.C₆​H₅​H₂​C− is a resonating structure. Normally resonance effect is more compared to other effects.
But since Cl³​C⁻ has 3 Cl group −I effect, inductive effect overruns resonance effect.

The correct order of basicity is
RCOO^- < CH≡C^- < NH₂^- < R^-
The reason behind is the electronegativity of atoms bearing negative charge. As the electronegativity of carbon is the least, it can donate its electron more freely. Similarly we can apply this on other compounds of this group. (Note that electronegativity of sp hybridised C atom is greater than sp³ hybridised N atom).

The correct answer is option B
CH₃CH₂CH(Cl)COOH is the strongest acid due to the presence of one −I effect chlorine at α-carbon increases the acid strength significantly.