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Applications: stability of carbocations, carbanions, free radicals

55 questions on Applications: stability of carbocations, carbanions, free radicals from the General Organic Chemistry I: Electronic Effects chapter: 11 NEET level, 22 JEE Main, 22 JEE Advanced. Each one opens with its answer and solution.

Practice this topic All General Organic Chemistry I: Electronic Effects topics

Which of the following carbanions is the most stable? JEE Main level
Consider I 1-methylcyclopentyl cation, II cyclopentyl cation and III bicyclo[2.2.1]hept-1-yl cation (cation at the bridgehead carbon). The correct order of stab... JEE Advanced level
Which of the following statements are correct? JEE Advanced level
The three species cyclopentadienyl cation, cyclopentadienyl radical and cyclopentadienyl anion (each planar, C5H5 with charge +, none, -) are compared. The corr... JEE Advanced level
Free-radical bromination of 2,3-dimethylbutane, (CH3)2CH-CH(CH3)2, with Br2 and light is very selective. The major monobromo product is: JEE Advanced level
Which of the following free radicals is the most stable? NEET level
Which of the following carbanions is the most stable? NEET level
Which of the following carbocations is the most stable? JEE Main level
Consider the acidity of the benzylic hydrogens in I 4-nitrotoluene, II toluene and III 4-methoxytoluene. The correct order of decreasing acidity is: JEE Advanced level
Which hydrogen of propene, CH3-CH=CH2, is abstracted most easily by a free radical such as Br^bullet? JEE Main level
Consider the carbocation (CH3)2CH-CH2-C+(CH3)-CH2CH3. The number of hyperconjugative structures equals the number of alpha hydrogens, i.e. hydrogens on the sp3 ... JEE Main level
Which is the correct order of acidity of the C-H bond in nitromethane, acetone, acetonitrile and methane? JEE Main level
Which of the following carbocations is the least stable? JEE Main level
Which of the following carbocations is the most stable? NEET level
Which is the correct order of acidity of the C-H bonds of ethane, ethene and ethyne? JEE Main level
Which is the correct order of stability of the following carbanions? JEE Main level
Which is the correct order of stability of the following free radicals? JEE Main level
In which of the following is the C-H bond the most acidic? JEE Main level
Which of the following free radicals are stabilised by resonance? JEE Main level
Which of the following carbocations is the most stable? JEE Main level
Which of the following statements about free radicals are correct? JEE Advanced level
In the triphenylmethyl cation, (C6H5)3C+, the positive charge is shared by the central carbon and by the ortho and para carbons of each ring in the various reso... JEE Advanced level
Which of the following hydrocarbons is the most acidic? NEET level
3-Methylbut-1-ene, CH2=CH-CH(CH3)2, loses its tertiary allylic hydrogen to a bromine radical. Which statement about the radical formed is correct? JEE Advanced level
Consider the carbocations I bis(4-methoxyphenyl)methyl cation, II diphenylmethyl cation and III bis(4-nitrophenyl)methyl cation. The correct order of stability ... JEE Advanced level
Considering only the +I effect of alkyl groups, which carbanion is the most stable? NEET level
Removal of H+ from which of the following hydrocarbons gives an aromatic carbanion? (Assume the anion is planar.) JEE Advanced level
Which of the following carbocations is the least stable? JEE Main level
Which statement about the allyl cation, allyl radical and allyl anion, CH2=CH-CH2 with charge +, one electron, or -, is correct? JEE Main level
Which of the following carbocations is the most stable? NEET level
Consider the C-H acidity of I cyclopenta-1,3-diene, II ethyne, III propene (most acidic H) and IV propane (most acidic H). The correct order of decreasing acidi... JEE Advanced level
Which of the following carbocations is the most stable? NEET level
Consider the free radicals I cyclohex-2-en-1-yl, II tert-butyl, III ethyl and IV methyl. The correct order of decreasing stability is: JEE Advanced level
Which of the following C-H bonds has the lowest bond dissociation energy? JEE Main level
Which of the following free radicals is the most stable? NEET level
The alkene 3,3-dimethylbut-1-ene, (CH3)3C-CH=CH2, adds a proton at the terminal carbon to give a secondary cation, which then undergoes a single 1,2-shift to a ... JEE Advanced level
The number of hyperconjugative structures of the ethyl cation, CH3CH2+, is (equal to the number of alpha hydrogens on the sp3 carbon attached to the cationic ca... NEET level
Which of the following carbanions is stabilised by resonance? NEET level
Which of the following carbanions is the most stable? JEE Main level
Which of the following species, assumed planar and fully conjugated, are antiaromatic? JEE Advanced level
In the tert-butyl cation, (CH3)3C+, the positively charged carbon is: NEET level
Cyclohepta-1,3,5-triene reacts with triphenylmethyl cation, (C6H5)3C+, by transfer of a hydride ion from its CH2 group to give C7H7+ and triphenylmethane. The m... JEE Advanced level
Which statement about the phenyl anion, C6H5^-, formed by removing H+ from benzene is correct? JEE Advanced level
Arrange the following anions in decreasing order of basic strength: I CH3CH2^-, II NH2^-, III HC#C^-, IV OH^-. JEE Advanced level
Which of the following statements about the geometry of the central carbon are correct? JEE Main level
In which of the following conversions does a carbocation change into a more stable carbocation by a single 1,2-shift? JEE Advanced level
Which of the following carbocations is the most stable? JEE Main level
Which of the following carbocations is the least stable? JEE Main level
Which of the following halides ionises most readily to a carbocation (heterolysis of the C-Br bond)? JEE Advanced level
Which of the following statements about the acidity of C-H bonds are correct? JEE Main level
The carbanion is formed by removing a proton from the methyl group of hexa-2,4-dienenitrile, CH3-CH=CH-CH=CH-C#N (C-1 is the nitrile carbon, the methyl group is... JEE Advanced level
Assuming each species is planar, which of the following are aromatic? JEE Main level
Which of the following carbanions are more stable than the ethyl carbanion, CH3CH2^-? JEE Advanced level
Cation I is 4-(dimethylamino)benzyl cation. Cation II is 4-(dimethylamino)-3,5-dimethylbenzyl cation (the two methyl groups are ortho to the N(CH3)2 group). Whi... JEE Advanced level
Which of the following carbocations are stabilised by resonance? JEE Main level