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Organic Chemistry – Some Basic Principles and Techniques · Question 32

AIPMT 2015 (Cancelled)MCQMedium📈 Topic in 25% papers+4−1
1

The enolic form of ethyl acetoacetate as shown below has [figure]

  1. 9 sigma bonds and 2 pi-bonds
  2. 9 sigma bonds and 1 pi-bond
  3. 18 sigma bonds and 2 pi-bonds
  4. 16 sigma bonds and 1 pi-bond.

Answer

(3) 18 sigma bonds and 2 pi-bonds

Solution

Enol form: CH3-C(OH)=CH-COOC2H5 ( C6H10O3)

Every bond has one σ bond; each double bond has one extra π bond.

σ bonds: C–H = 9, O–H = 1, C–C = 4, C–O = 4 ⇒ total = 18

(check: open-chain molecule with 19 atoms ⇒ 19 − 1 = 18 σ bonds)

π bonds: one C=C and one C=O ⇒ 2

Answer: (3)

AIPMT 2015 (Cancelled)

Keep practising — Organic Chemistry – Some Basic Principles and Techniques

2

In which of the following compounds, the C–Cl bond ionisation shall give most stable carbonium ion?

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
AIPMT 2015 (Cancelled)
3

Given : [figure] The enthalpy of hydrogenation of these compounds will be in the order as

  1. II > III > I
  2. II > I > III
  3. I > II > III
  4. III > II > I
AIPMT 2015 (Cancelled)
4

Which of the following organic compounds has same hybridization as its combustion product (CO2)?

  1. Ethane
  2. Ethyne
  3. Ethene
  4. Ethanol
AIPMT 2014
5

The radical, [figure] is aromatic because it has

  1. 7 p-orbitals and 7 unpaired electrons
  2. 6 p-orbitals and 7 unpaired electrons
  3. 6 p-orbitals and 6 unpaired electrons
  4. 7 p-orbitals and 6 unpaired electrons.
NEET 2013
6

The structure of isobutyl group in an organic compound is

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
NEET 2013
7

Structure of the compound whose IUPAC name is 3-Ethyl-2-hydroxy-4-methylhex-3-en-5-ynoic acid is

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
NEET 2013
8

The outer orbitals of C in ethene molecule can be considered to be hybridized to give three equivalent sp2 orbitals. The total number of sigma (σ) and pi (π) bonds in ethene molecule is

  1. 3 sigma (σ) and 2 pi (π) bonds
  2. 4 sigma (σ) and 1 pi (π) bonds
  3. 5 sigma (σ) and 1 pi (π) bonds
  4. 1 sigma (σ) and 2 pi (π) bonds
NEET 2013 (Karnataka)
9

Arrange the following in increasing order of stability 1. (CH3)2- C-CH2-CH3 2. (CH3)3- C 3. (CH3)2- CH 4. CH3- CH2 5. CH3

  1. 5 < 4 < 3 < 1 < 2
  2. 4 < 5 < 3 < 1 < 2
  3. 1 < 5 < 4 < 3 < 2
  4. 5 < 4 < 3 < 2 < 1
NEET 2013 (Karnataka)
10

What is the hybridisation state of benzyl carbonium ion? [figure]

  1. sp2
  2. spd2
  3. sp2d
  4. sp3
NEET 2013 (Karnataka)
11

Homolytic fission of the following alkanes forms free radicals CH3-CH3, CH3-CH2-CH3, (CH3)2CH-CH3, CH3-CH2-CH(CH3)2. Increasing order of stability of the radicals is

  1. (CH3)2 C-CH2CH3 < CH3- CH-CH3 < CH3- CH2 < (CH3)3 C
  2. CH3- CH2 < CH3- CH-CH3 < (CH3)2 C-CH2-CH3 < (CH3)3 C
  3. CH3- CH2 < CH3- CH-CH3 < (CH3)3 C < (CH3)2 C-CH2CH3
  4. (CH3)3 C < (CH3)2 C-CH2CH3 < CH3- CH-CH3 < CH3- CH2
NEET 2013 (Karnataka)

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