NEET

Which one of the following orders is correct regarding the–I effect of the substituents ?

—NR₂ < —OR > —F
—NR₂ > —OR > —F
—NR₂ < —OR < —F
—NR₂ > —OR < —F

Solution

The atom or group which has more power to attract electrons in comparision to hydrogen is said to have-I effect. Thus higher the electronegativity of atom stronger will be the -I effect. As electronegativity of N,O and F follow the order N < O < F hence based upon electronegative character order of-I effect is –NR₂ < –OR < –F.

Which one of the following compounds is resistant to nucleophilic attack by hydroxyl ions ?

Methyl acetate
Acetonitrile
Diethyl ether
Acetamide

Solution

a
b
c
d

Solution

–OCH₃ activates the benzene ring. –NO₂ deactivates the ring. Hence the reaction of the given compounds with electrophiles is in the order, I >II > III.

a
b
c
d

Solution

Peroxide ion is more nucleophilic but less basic than OH^–.

\({S_{E}}^{2}\)
\({S_{N}}^{1}\)
\({S_{N}}^{0}\)
\({S_{N}}^{2}\)

Solution

Decreasing order of reactivity towards nucleophilic addition to carbonyl group among cyclopentanone,3-pentanone and n-pentanal is

3-pentanone,cyclopentanone,n-pentanal
n-pentanal, 3-pentanone,cyclopentanone
n-pentanal, cyclopentanone, 3-pentanone
cyclopentanone, 3-pentanone,n-pentanal

Solution

Which is true regarding the relative basic character of the following two pairs?

NH₃ > NH₂OH
–CCl₃ > –CF₃
Both are true
Nither is true

Solution

Which of the following is maximum stable

Conjugated alkadiene (CH₂ = CH – CH = CH₂)
Isolated alkadiene (CH₂ = CH – CH₂- CH = CH₂)
Cumulated alkadiene(CH₂= C = CH₂)
All are equal

Solution

Due to resonance conjugated alkadiene is maximum stable. Isolated is more stable than cumulated alkadiene.

Which is weakest base :

C₆H₅– CH₂– NH₂
C₆H₅– CH₂– NH –CH₃
O₂N – CH₂– NH₂
CH₃– NH – CHO

Solution

Due to resonance of lone pair.

Which of the following is true?

A c is isomer has lower b.p.than the trans
A c is isomer has lower m.p. than the tans
All isomers of nitrophenols are equal soluble in water
All the three are correct

Solution

A c is-isomer has higher b.p. due to polar (or more polar)nature but lower m.p. due to a symmetry than the trans-isomer. Among three isomeric nitrophenols, o-isomer forms intra molecular bonding so H-bonding with water will be restricted.

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