Basics of Organic Chemistry (GOC)

NEET Chemistry · 63 questions · Page 7 of 7 · Click an option or "Show Solution" to reveal answer

Q61

The correct acidic order of the following is

A I > II > III

B III > I > II

C II > III > I

D I > III > II

Correct Answer

Option B

Solution

Presence of electron withdrawing groups (– NO 2 , –X, – CN) increase the acidity of phenols while the presence of electron releasing groups (– NH 2 , – CH 3 ) decrease the acidity of phenols.

This explains the following order of acidity. p-nitrophenol > phenol > p-cresol.

Q62

A compound of molecular formula C 7 H 16 shows optical isomerism, compound will be

A 2, 3-dimethylpentane

B 2, 2-dimethylbutane

C 2-methylhexane

D none of these

Correct Answer

Option A

Solution

Organic compounds exhibit the property of enantiomerism (optical isomerism) only when their molecules are chiral.

Most chiral compounds have a chiral centre, which is an atom bonded to four different atoms or groups.

2,3-Dimethylpentane has one chiral C-atom and do not have any symmetric element.

Q63

Which of the following is correct with respect to – I effect of the substituents? (R = alkyl)

A – NH 2 < – OR < – F

B – NR 2 < – OR < – F

C – NH 2 > – OR > – F

D – NR 2 > – OR > – F

Correct Answer

Option A

Solution

– I effect increases on increasing electronegativity of atom.

So, correct order of – I effect is – NH 2 < – OR < – F Also, – NR 2 < – OR < – F

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