Q.1. A tertiary butyl carbocation is more stable than a secondary butyl carbocation because of which of the following? (2020)
A: –R effect of –CH3 groups
C: –I effect of –CH3 groups
D: + R effect of –CH3 groups
Q.2. The number of sigma (σ) and pi (π) bonds in pent-2-en-4-yne is (2019)
A: 10σ bonds and 3π bonds
B: 8σ bonds and 5π bonds
C: 11σ bonds and 2π bonds
D: 13σ bonds and no π bonds
Number of σ bonds = 10
and Number of π bonds = 3
Q.3. The compound that is most difficult to protonate is : (2019)
Due to involvement of lone pair of electrons in resonance in phenol, it will have positive charge (partial). Hence, incoming proton will not be able to attack easily.
Q.4. A mixture of 2.3 g formic acid and 4.5 g oxalic acid is treated with conc. H2SO4. The evolved gaseous mixture is passed through KOH pellets. Weight (in gm) of the remaining product at STP will be (2018)
Q.5. Which of the following is correct with respect to -I effect of the substituents? (R= alkyl) (2018)
A: - NH2 < - OR < - F
B: - NR2 < - OR < - F
C: - NH2 > - OR > - F
D: - NR2 > - OR > - F
(Based on EN)
∴ -NH2 < -OR < -F -I effect
Also -NR2 < -OR < -F -I effect
Q.6. Which of the following carbocations is expected to be most stable ? (2018)
-NO2 group is meta-directing group
(Less stable due to more e- with drawing effect of -NO2)
(More stable due to less e- with drawing effect of -NO2)
Q.7. Which one is the most acidic compound ? (2017)
Q.8. The correct increasing order of basic strength for the following compounds is: (2017)
A: III < I < II
B: III < II < I
C: II < I < III
D: II < III < I
Q.9. The IUPAC name of the compound
Q.10. The correct statement regarding electrophile is (2017)
A: Electrophile is a negatively charged species and can form a bond by accepting a pair of electrons from another electrophile
B: Electrophiles are generally neutral species and can form a bond by accepting a pair of electrons from a nucleophile
C: Electrophile can be either neutral or positively charged species and can form a bond by accepting a pair of electrons from a nucleophile
D: Electrophile is a negatively charged species and can form a bond by accepting a pair of electrons from a nucleophile
Electrophile can be either neutral or positively charged species and can form a bond by accepting a pair of electron from a nucleophile.
Q.12. With respect to the conformers of ethane, which of the following statements is true ? (2017)
A: Bond angle changes but bond length remains same
B: Both bond angle and bond length change
C: Both bond angles and bond length remains same
D: Bond angle remains same but bond length changes
In conformation bond angle and bond length remain same.
Q.12. The correct statement regarding the comparison of staggered and eclipsed conformations of ethane, is: (2016)
A: The staggered conformation of ethane is more stable than eclipsed conformation, because staggered conformation has no torsional strain.
B: The staggered conformation of ethane is less stable than eclipsed conformation, because staggered conformation has torsional strain.
C: The eclipsed conformation of ethane is more stable than staggered conformation, because eclipsed conformation has no torsional strain.
D: The eclipsed conformation of ethane is more stable than staggered conformation even though the eclipsed conformation has torsional strain.
Magnitude of torsional strain depends upon the angle of rotation about C-C bond. Staggered form has the least torsional strain and the eclipsed form has the maximum torsional strain. So, the staggered conformation of ethane is more stable than the eclipsed conformation.
Q.13. Which of the following biphenyls is optically active (2016)
O-Substituted biphenyls are optically active as both the rings are not in one plane and their mirror images are non-superimposable.
Q.14. The enolic form of ethyl acetoacetate as below has : (2015)
A: 9 sigma bonds and 1 pi - bond
B: 18 sigma bonds and 2 pi - bonds
C: 16 sigma bonds and 1 pi-bond
D: 9 sigma bonds and 2 pi - bonds
Q.15. Consider the following compounds (2015)
Hyperconjugation occurs in :
A: I and III
B: I only
C: II only
D: III only
Hyperconjugation occurs through the H- atoms present on the carbon atom next to the double bond i.e alpha hydrogen atoms. There is no alpha -H in the structure I and II.
So, hyperconjugation occurs in structure III only ie.
Q.16. Which of the following is the most correct electron displacement for a nucleophilic reaction to take place ? (2015)
Allylic and benzylic halides show high reactivity towards Sn1 reaction Further, due to greater stabilisation of allyl and benzyl carbocations intermediates by resonance, primary allylic and primary benzylic halides show higher reactivity in Sn1 reactions than other simple primary halides.
Hence, it undergoes nucleophilic reaction readily.
Q.17. The total number of π -bond electrons in the following structure is : (2015)
Q.18. In which of the following compounds, the C - Cl bond ionisation shall give most stable carbonium ion ? (2015)
3° carbocation are more stable than benzylic carbocation.
Q.19. In Duma's method for estimation of nitrogen, 0.25 g of an organic compound gave 40 mL of nitrogen collected at 300 K temperature and 725 mm pressure. If the aqueous tension at 300K is 25mm, the percentage of nitrogen in the compound is : (2015)
Q.20. Given :
Q. Which of the given compounds can exhibit tautormerism ? (2015)
A: I, II and III
B: I and II
C: I and III
D: II and III
In keto-enol tautomerism,
Q.21. In the Kjeldahl's method for estimation of nitrogen present in a soil sample, ammonia evolved from 0.75 g of sample neutralized 10 mL of 1M H2SO4. The percentage of nitrogen in the soil is : (2014)