CSIR-NET CHEMICAL SCIENCES | Principles of stereochemistry

Principles of stereochemistry: Configurational and conformational isomerism in acyclic and cyclic compounds; stereogenicity, stereoselectivity, enantioselectivity, diastereoselectivity and asymmetric induction.

YEAR JUN-2016 DEC-2015 JUN-2015 DEC-2014 JUN-2014 DEC-2013 JUN-2013 DEC-2012 JUN-2012 DEC-2011 JUN-2011
No.of questions appeared 6 5 5 2 5 4 4 4 3 2 6

1.In the following compound, the stereo-chemical descriptor for Ha and Hb is…..

stereo-chemiostry-csir-ugc-net-chemical-sciences

(1) enantiotopic

(2) diastereotopic

(3) homotopic

(4) constitutionally heterotopic

 

2. The correct statements about conformations X and Y of 2-butanone are

2. The correct statements about conformations X and Y of 2-butanone are A. X is more stable than Y B. Y is more stable than X C. Methyl groups in X are anti D. Methyl groups in Y are gauche (1) A and D (2) A and C (3) B and C (4) A, C and D <div id="“post1”-link-562" class="sh-link “post1”-link sh-hide"><a href="#" onclick="showhide_toggle('“post1”', 562, 'Show Answer ', 'Hide Answer '); return false;" aria-expanded="false"><span id="“post1”-toggle-562">Show Answer </span></a></div><div id="“post1”-content-562" class="sh-content “post1”-content sh-hide" style="display: none;"> Ans (4) Soln: Conformation X & Y are as follows Statement: A. ‘X’ is more stable than ‘Y’ is correct because methyl groups in ‘X’ are anti B. ‘Y’ is more stable than ‘X’ is incorrect statement C. Methyl group in ‘X’ are anti is correct statement D. Methyl groups in ‘Y’ are gauche is correct statement So, statement ‘A’, ‘C’ & ‘D’ are correct for structure ‘X’ & ‘Y’ </div>

  1. X is more stable than Y
  2. Y is more stable than X
  3. Methyl groups in X are anti
  4. Methyl groups in Y are gauche

(1) A and D

(2) A and C

(3) B and C

(4) A, C and D

 

3.The correct order of the magnitude of ‘A values’ for the given substituents in cyclohexane derivatives is

3-stereo-chemistry-csir-net-gate-chemical-science-june-2016

(1) Ph> CN > Me

(2) Me >Ph>CN

(3) CN > Me >Ph

(4) Ph> Me > CN

 

4.The major product formed in the following reaction sequence is                   

 4-robinson-stereo-chemistry-csir-net-gate-chemical-science-june-2016

 

5.The correct structure of the intermediate, which leads to the product in the following reaction, is

2-stereo-chemistry-csir-net-gate-chemical-science-june-2016

 

6.The major product formed in the following reaction is

2-stereo-chemistry-csir-net-gate-chemical-science-june-2016

 

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