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Organic Chemistry – Some Basic Principles and Techniques · Question 54

AIPMT 2008MCQEasy📈 Topic in 0% papers+4−1
1

The stability of carbanions in the following [figure] is in the order of

  1. (iv) > (ii) > (iii) > (i)
  2. (i) > (iii) > (ii) > (iv)
  3. (i) > (ii) > (iii) > (iv)
  4. (ii) > (iii) > (iv) > (i)

Answer

(3) (i) > (ii) > (iii) > (iv)

Solution

As per NCERT, a carbanion is more stable when the carbon carrying the negative charge has more s-character, because an s-rich orbital holds the lone pair closer to the nucleus.

(i) RC C: the charge is on an sp carbon (50% s-character) — most stable.

(ii) phenyl carbanion and (iii) vinyl carbanion: the charge is on an sp2 carbon (33% s-character); in (ii) the lone pair is further stabilised by the -I effect of the sp2 carbons of the ring, so (ii) > (iii).

(iv) R3C- CH2: the charge is on an sp3 carbon (25% s-character) and the alkyl group (+I effect) pushes more electron density onto it — least stable.

Order of stability: (i) > (ii) > (iii) > (iv)

Answer: (3)

AIPMT 2008

Keep practising — Organic Chemistry – Some Basic Principles and Techniques

2

In the hydrocarbon, 6CH3- 5CH= 4CH- 3CH2- 2C 1CH The states of hybridization of carbons 1, 3 and 5 are in the following sequence

  1. sp, sp2, sp3
  2. sp3, sp2, sp
  3. sp2, sp, sp3
  4. sp, sp3, sp2
AIPMT 2008
3

For (i) I-, (ii) Cl-, (iii) Br-, the increasing order of nucleophilicity would be

  1. Cl- < Br- < I-
  2. I- < Cl- < Br-
  3. Br- < Cl- < I-
  4. I- < Br- < Cl-
AIPMT 2007
4

Consider the following compounds (i) C6H5COCl (ii) [figure] (iii) [figure] (iv) [figure] The correct decreasing order of their reactivity towards hydrolysis is

  1. (i) > (ii) > (iii) > (iv)
  2. (iv) > (ii) > (i) > (iii)
  3. (ii) > (iv) > (i) > (iii)
  4. (ii) > (iv) > (iii) > (i)
AIPMT 2007
5

The general molecular formula, which represents the homologous series of alkanols is

  1. CnH2nO
  2. CnH2nO2
  3. CnH2n+2O
  4. CnH2n+1O
AIPMT 2006
6

The IUPAC name of [figure] is

  1. 1-chloro-1-oxo-2, 3-dimethylpentane
  2. 2-ethyl-3-methylbutanoyl chloride
  3. 2, 3-dimethylpentanoyl chloride
  4. 3, 4-dimethylpentanoyl chloride.
AIPMT 2006
7

The general molecular formula, which represents the homologous series of alkanols is

  1. CnH2n+2O
  2. CnH2nO2
  3. CnH2nO
  4. CnH2n+1O
AIPMT 2006
8

Names of some compounds are given. Which one is not in IUPAC system?

  1. CH3-CH2-CH2- CH2CH3 |CH- CH3 |CH-CH2CH3 3-Methyl-4-ethylheptane
  2. CH3- OH |CH- CH3 |CH-CH3 3-Methyl-2-butanol
  3. CH3-CH2- CH2 \|C- CH3 |CH-CH3 2-Ethyl-3-methylbut-1-ene
  4. CH3-C C-CH(CH3)2 4-Methyl-2-pentyne
AIPMT 2005
9

Which amongst the following is the most stable carbocation?

  1. CH3
  2. CH3 CH2
  3. CH3- CH3 | CH
  4. CH3- CH3 | CH3 | C
AIPMT 2005
10

Name of the compound given below is [figure]

  1. 4-ethyl-3-methyloctane
  2. 3-methyl-4-ethyloctane
  3. 2,3-diethylheptane
  4. 5-ethyl-6-methyloctane
AIPMT 2003
11

Which one of the following orders of acid strength is correct ?

  1. RCOOH > ROH > HOH > HC CH
  2. RCOOH > HOH > ROH > HC CH
  3. RCOOH > HOH > HC CH > ROH
  4. RCOOH > HC CH > HOH > ROH
AIPMT 2003

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