Some Basic Principles of Organic Chemistry Previous Year Questions

NEET, JEE Main Previous Year Questions Solutions for Class 11th Chemistry Chapter 12 Organic Chemistry  Some Basic Principles and Techniques...

NEET, JEE Main Previous Year Questions Solutions for Class 11th Chemistry Chapter 12 Organic Chemistry Some Basic Principles and Techniques / Special Cases JEE MAINS - NEET

NEET Previous Year Questions of Organic Chemistry - Some Basic Principles and Techniques

The students who are targeting NEET 2021 exam should prepare for all the important chapters of NEET syllabus to secure highest marks in NEET 2021 and NEET 2022. This questions for NEET 2020 designed by  analyzing the previous years question paper and considering the weightage.

According to the NEET Chapter Wise Weightage Organic Chemistry - Some basic Principle and techniques chapter contributes for around 3% of the total number of questions asked in the last 32 years.

Last 7 Years NEET/AIPMT Sub-Topic wise Weightage Analysis for Organic Chemistry - Some basic Principle and techniques:

Now that you are aware of the topic & sub-topic analysis, the next step would be to prepare yourself for the questions that have already been asked in the previous papers for these topics.

NEET 2020 F 1: A tertiary butyl carbocation is more stable than a secondary butyl carbocation because of which of the following ?

(1) - R effect of - CH₃ groups (2) Hyperconjugation (3) - I effect of - CH₃ groups (4) + R effect of - CH₃ groups

5. The correct statement regarding electrophile is                                                                   NEET- 2017

(a) Electrophile is a negatively charge species and can form a bond by accepting a pair of electrons from a nucleophile 

(b) Electrophile is a negatively charged species and can form a bond by accepting a pair of electrons from another electrophile 

(c) Electrophiles are generally neutral species and can form a bond by accepting a pair of electrons from a nucleophile 

(d) Electrophile can be either neutral or positively charged species and can form a bond by accepting a pair of electrons from a nucleophile 

Concept Questions :-   Nucleophile and Electrophile

6. With respect to the conformers of ethane, which of the following statements is true?    NEET- 2017

(a) Bond angle remains same but bond length changes 

(b) Bond angle changes but bond length remains same 

(c) Both bond angle and bond length change 

(d) Both bond angles and bond length remain same 

Concept Questions :- Conformational Isomers

7. The IUPAC name of the compound                NEET- 2017

1. 3-keto-2-methylhex-4-enal 

2. 5-formylhex-2-en-3-one 

3. 5-methyl-4-oxohex-2-en-5-al 

4. 3-keto-2-methylhex-5-enal 

8. Which one is the correct order of acidity?     NEET- 2017

(a) CH₂=CH₂ > CH₃-CH=CH₂ > CH₃CECH > CH≡CH

(b) CH≡CH > CH₃-C≡CH > CH₂=CH₂ > CH₃-CH₃

(c) CH≡CH > CH₂=CH₂ > CH₃-C≡CH > CH₃-CH₃

 (d) CH₃-CH₃ > CH₂=CH₂ > CH₃-C≡CH > CH≡CH

Concept Questions :- Acidic and Basic Character

9. The most suitable method of separation of 1:1 mixture of ortho and para-nitrophenols is   NEET-2017

(a) sublimation (b) chromatography (c) crystallisation (d) steam distillation 

Concept Questions :- Purification of Organic Compounds, Cromatography and Distillation

Q 10. NEET 2016

Q 11. NEET 2016

Q 12. NEET 2016

13. The correct statement regarding the comparison of staggered and eclipsed conformations of ethane, is NEET- 2016

(a) The eclipsed conformation of ethane is more stable than staggered conformation. because eclipsed conformation has no torsional strain 

(b) The eclipsed conformation of ethane is more stable than staggered conformation even though the eclipsed conformation has torsional strain 

(c) The staggered conformation of ethane is more stable than eclipsed conformation, because staggered conformation has no torsional strain 

(d) The staggered conformation of ethane is less stable than eclipsed conformation. because staggered conformation has torsional strain 

14. In which of the following compounds, the C- CI bond ionisation shall give most stable carbonium ion ? NEET- 2015

Ans - C

15. consider the following compounds  NEET- 2015

hyperconjugation occurs in (a) I only (b) II only (c) III only (d) I and Ill 

Concept Questions :- Hyperconjugation Effects

16. The enolic form of ethyl acetoacelate as below has:-  NEET 2015

(a) 18 sigma bonds and 2 pi-bonds (b) 16 sigma bonds and 1 pi-bond (c) 9 sigma bonds and 2 pi-bonds (d) 9 sigma bonds and 1 pi-bond 

Concept Questions :- Shape, Hybridisation and Structure of Carbon Compounds

17. Which of the given compounds can exhibit tautomerism? NEET- 2015

(a) I and II (b) I and III (c) II and III (d) I, II and III 

Concept Questions :- Structural Isomer

18. Which of the following statements is not correct for a nucleophile? NEET 2015

(a) Nucleophile is a Lewis acid (b) Ammonia is a nucleophile (c) Nucleophiles attack low electrons density sites (d) Nucleophiles are not electron seeking 

Concept Questions :- Nucleophile and Electrophile

19. In the Kjeldahl's method for estimation of nitrogen present in a soil sample, ammonia evolved from 0.75 g of sample neutralised 10 mL of 1 M H2SO4. The percentage of nitrogen in the soil is- NEET 2014

1. 37.33 2. 45.33 3. 35.33 4. 43.33 

Concept Questions :- Quantitative Analysis of Organic Compounds

20. Which one is most reactive towards nucleophilic addition reaction?  NEET 2014

Concept Questions :- Nucleophile and Electrophile

21. Structure of the compound whose IUPAC name is 3-ethy1-2-hydroxy-4-methylhex-3-en-5-ynoic acid is ? NEET 2013

22. The structure of isobutyl group in an organic compound is NEET 2013

23. Some meta-directing substituents in aromatic substitution are given. Which one is most deactivating? NEET 2013

(a) -C≡N (b) -SO₃H (c) -COOH (d) -NO₂  

24. The radical 

 is aromatic because it has NEET 2013

(a) 6 p-orbitals and 6 unpaired electrons (b) 7 p-orbitals and 6 unpaired electrons (c) 7 p-orbitals and 7 unpaired electrons (d) 6 p-orbitals and 7 unpaired electrons 

25. The order of stability of the following tautomeric compound is NEET 2013

a) 1>2>3

b) 3>2>1

c) 2>1>3

d) 2>3>1

26. Among the following compounds the one that is most reactive towards electrophilic nitration is NEET 2013
(a) benzoic acid (b) nitrobenzene (c) toluene (d) benzene

27. The correct order of decreasing acid strength of trichloroacetic acid (A), trifluoroacetic acid (B), acetic acid (C) and formic acid (D) is  NEET 2012

(a) B>A>D>C (b) B>D>C>A (c) A>B>C>D (d) A>C>B>D 

Concept Questions :- Acidic and Basic Character

28. Which nomenclature is not according to IUPAC system? NEET 2012

Ans= 1

29. Which of the following does not exhibit optical isomerism? NEET 2012

(a) Maleic acid

(c) Lactic acid

(b) a-amino acids

(d) Tartaric acid

30. The correct IUPAC name of the compound         NEET 2011

(a) 3-ethyI-4-ethenyIheptane

(b) 3-ethyI-4-propyIhex-5-ene

(c) 3-(1-ethyl propyl) hex-I -ene

(d) 4-ethyI-3-propyIhex-I -ene

31. Which one of the following is most reactive towards electrophilic reagent?      NEET 2011

Concept Questions :- Nucleophile and Electrophile

Ans=1

32. In Duma's method of estimation of nitrogen 0.35 g of an organic compound gave 55 ml of nitrogen collected at 300 K temperature and 715 mm pressure. The percentage composition of nitrogen in the compound would be (Aqueous tension at 300 K, 15 mm)           NEET 2011

1. 16.45

2. 17.45

3. 14.45

4. 15.45

Concept Questions :- Quantitative Analysis of Organic Compounds

33. The Lassaigne's extract is boiled with con. HN03 while testing for halogens. By doing so it.  NEET 2011

1. helps in the precipitation of AgCl

2. increases the solubility product of AgCl

3. increases the concentration of N03- ions

4. decomposes Nas and NaCN, if formed.

34. Which one of the following has the most acidic nature? NEET 2010

Ans =b 

35. The correct order of increasing reactivity of C-X bond towards nucleophile in the following compounds is NEET 2010

(a) I < II < IV < III (b) II < III < I < IV (c) IV < III < I < IV (d) III < II < I < IV 

36. Among the given compounds, the most susceptible to nucleophilic attack at the carbonyl group is NEET 2010

1. CH₃COOCH₃

2. CH₃CONH₂

3. CH₃COOCOCH₃

4. CH₃COCl

37. Which one is most reactive towards electrophilic reagent? NEET 2010

Concept Questions :- Nucleophile and Electrophile

Ans= 1

38. The II-JPAC name of the compound having the formula CH≡C-CH=CH₂ is  NEET 2019

(a) 3-butene-l -yne

(b) I-butyn-3-ene

(c) but-I-yne-3-ene

(d) I-butene-3-yne

39. The relative reactivates of acyl compounds towards nucleophilic substitution are in the order of NEET 2008

(a) Acyl chloride > Acid anhydride > Ester > Amide

(b) Ester > Acyl Chloride > Amide > Acid anhydride

(c) Acid anhydride > amide > Ester > Acyl chloride

(d) Acyl chloride > Ester > Acid anhydride > Amide

40. Which one of the following is most reactive towards electrophillic attack? NEET 2008

A)    (a)  C₆H₅−CH₂OH

B)   (b)  C₆H₅−NO₂

C)    (c) C₆H₅−OH

D)    (d) C₆H₅−Cl

41.Base strength of     NEET 2008

(1) H₃CCH₂      (2) H₂C=CH and     (3) H-C=C 

(a) (2) > (1) > (3) (c) (1) > (3) > (2) (b) (3) > (2) > (1) (d) (1) > (2) > (3) 

Concept Questions :- Electron Displacement Effects

42. A strong base can abstract an a-hydrogen from  NEET 2008

(a) alkene

(c) ketone

(b) amine

(d) alkane

43.The stability of carbanions in the following  NEET 2008

is in the order of (a) (1)>(2)> (3)>(4) (b) (2)>(3)>(4)>(1) (c) (4)>(2)>(3)>(1) (d) (1)>(3)>(2)>(4) 

Concept Questions :- Reaction Intermediates

44. Which of the following represents the correct order of the acidity in the given compounds ?    NEET 2007

(a) CH₃COOH > BrCH₂COOH > CICH₂COOH > FCH₂COOH

(b) FCH₂COOH > CH₃COOH > BrCH₂COOH > CICH₂COOH

(c) BrCH₂COOH > CICH₂COOH > FCH₂COOH > CH₃COOH

(d) FCH₂COOH > CICH₂COOH > BrCH₂COOH > CH₃COOH

Concept Questions :- Electron Displacement Effects

45. If there is no rotation of plane polarized light by a compound in a specific solvent, thought to be chiral, it may mean that:   NEET 2007

(a) the compound is certainly a chiral

(b) the compound is certainly meso

(c) there is no compound in the solvent

(d) the compound may be a racemic mixture

Concept questions: optical isomerism for neet

46. For the following : (i) I^-     (ii) CI^-     (iii) Br^{-      NEET 2007}

the increasing order of nucleophilicity would be : (a) I^-<Br^- <CI^-(b) CI^- < Br^- < I^- (c) I^- <CI^- < Br^- (d) Br^- < CI^- < I^-

Concept Questions :- Nucleophile and Electrophile

 47. The IUPAC name of       NEET 2006

1. 3, 4-dimethylpentanoyl chloride 

2. 1-chloro-1-oxo-2, 3-dimethylpentane 

3. 2-ethy1-3-methylbutanoyl chloride 

4. 2, 3-dimethylpentanoyl chloride

JEE Previous Year Questions of Organic Chemistry - Some Basic Principles and Techniques

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Explanation

(I) Shows hydrogen bonding from –OH group only.

(II) Shows strongest hydrogen bonding from both sides of –OH group as well as –NO₂ group.

(III) Shows stronger hydrogen from both side of –OH group as well as –NH₂ group.

(IV) Shows stronger hydrogen from one side –OH group and another side of –OCH₃ group shows only dipole-dipole interaction.

Hence correct order of boiling point is :

I < IV < III < II

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Explanation

Spent-lye and glycerol are separated by distillation under reduced pressure.

Under the reduced pressure the liquid boil at low temperature and the temperature of decomposition will not reach. e.g. glycerol boils at ${290}^{\circ }$$C$ with decomposition but at reduced pressure it boils at ${180}^{\circ }C$ without decomposition.

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Explanation

Moles of $HCl$ taken $=20\times 0.1\times {10}^{-3}=2\times {10}^{-3}$

Moles of $HCl$ neutralised by $NaOH$ solution

$=15\times 0.1\times {10}^{-3}=1.5\times {10}^{-3}$

Moles of $HCl$ neutralised by ammonia

$=2\times {10}^{-3}-1.5\times {10}^{-3}$

$=0.5\times {10}^{-3}$

$\%$ of nitrogen $=\frac{1.4\times N\times V}{w.t.ofSubs\tan ce}\times 100$

$=\frac{1.4\times 0.5\times {10}^{-3}}{29.5\times {10}^{-3}}\times 100=23.7\%$

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Explanation

NOTE : Among isomeric alkanes, the straight chain isomer has higher boiling point than the branched chain isomer. The greater the branching of the chain, the lower is the boiling point. Further due to the presence of $\pi$ electrons, these molecules are slightly polar and hence have higher boiling points than the corresponding alkanes.

Thus $B.pt.$ follows the order

alkynes $>$ alkene $>$ alkanes (straight chain) > branched chain alkanes.

Explanation

In aromatic acids presence of electron withdrawing substituent e.g. $-N{O}_2$ disperses the negative charge of the anion and stablises it and hence increases the acidity of the parent benzoic acid.

Further $O$- isomer will have higher acidity than corresponding $m$ and $p$ isomers. Since nitro group at $p$-position have more pronounced electron withdrawing than $-N{O}_2$ group at $m$-position hence the correct order is the one given above.