Hyperconjugation

28 questions on Hyperconjugation from the General Organic Chemistry I: Electronic Effects chapter: 6 NEET level, 12 JEE Main, 10 JEE Advanced. Each one opens with its answer and solution.

• Which of the following carbocations is the most stable on account of hyperconjugation? NEET level
• Hyperconjugation is also known as NEET level
• The number of alpha hydrogens (hence of hyperconjugative structures) in the tert-butyl cation (CH3)3C+ is NEET level
• Which of the following alkenes has the maximum number of hyperconjugative structures? NEET level
• In which of the following can hyperconjugation NOT operate? NEET level
• Hyperconjugation in propene involves the delocalisation of electrons of the NEET level
• The correct order of stability of the following carbocations is JEE Main level
• Which of the following alkenes has the lowest heat of hydrogenation (all give the corresponding alkane)? JEE Main level
• The carbocation CH3-CH2-C+(CH3)2 (2-methylbutan-2-yl cation) can be stabilised by hyperconjugation. The number of hyperconjugative (no-bond resonance) structure... JEE Main level
• The correct order of the hyperconjugation ability (Baker-Nathan order) of alkyl groups attached to a pi system is JEE Main level
• Which of the following carbocations is stabilised only by hyperconjugation and +I effect, with no resonance and no lone pair involvement? JEE Main level
• Which of the following has the maximum number of hyperconjugative structures? JEE Main level
• Assertion (A): The tert-butyl cation is more stable than the isopropyl cation. Reason (R): The tert-butyl cation has a larger number of hyperconjugative structu... JEE Main level
• The correct order of stability of the free radicals is JEE Main level
• On the basis of the +I effect of alkyl groups (and absence of any stabilising hyperconjugation for the negative centre), the correct order of stability of the c... JEE Main level
• In propene, CH3-CH=CH2, hyperconjugation takes place through overlap of JEE Main level
• Which of the following statements about hyperconjugation are correct? JEE Main level
• In which of the following can hyperconjugation operate? JEE Main level
• 2,3-Dimethylbut-2-ene, (CH3)2C=C(CH3)2, is protonated at one sp2 carbon to give the more stable carbocation. The number of hyperconjugative (no-bond resonance) ... JEE Advanced level
• Consider the alkenes (I) CH3CH=CHCH3, (II) (CH3)2C=CHCH3, (III) (CH3)2C=C(CH3)2 and (IV) (CH3)2C=CH2. The correct order of the number of hyperconjugative struct... JEE Advanced level
• Arrange in decreasing order of heat of hydrogenation (to the corresponding alkane): ethene, propene, but-2-ene, 2,3-dimethylbut-2-ene. JEE Advanced level
• The 3-methylbutan-2-yl cation, (CH3)2CH-CH+-CH3, rearranges by a 1,2-hydride shift to a more stable carbocation. The number of alpha C-H bonds changes from JEE Advanced level
• The correct order of stability of the carbocations (I) p-CH3O-C6H4-CH2+, (II) p-CH3-C6H4-CH2+, (III) C6H5-CH2+ and (IV) p-O2N-C6H4-CH2+ is JEE Advanced level
• The correct order of acid strength of benzoic acid (I), 4-methylbenzoic acid (II) and 4-nitrobenzoic acid (III) is JEE Advanced level
• Which of the following statements about the number of hyperconjugative structures are correct? JEE Advanced level
• Which of the following carbocations are stabilised by BOTH hyperconjugation and resonance? JEE Advanced level
• Which of the following carbocations will rearrange (by a 1,2-hydride or 1,2-methyl shift) to a more stable carbocation? JEE Advanced level
• Which of the following statements are correct? (Alkyl groups reduce acidity by +I effect and hyperconjugation.) JEE Advanced level