Exams › JEE Advanced › Chemistry

The hyperconjugative stabilisation of the tert-butyl cation and of 2-butene arise, respectively, from which electron delocalisations?

1. sigma -> p (empty) and sigma -> pi delocalisations
2. sigma -> sigma and sigma -> pi delocalisations
3. sigma -> p (filled) and sigma -> pi delocalisations
4. p (filled) -> sigma and sigma -> pi delocalisations

Correct answer: sigma -> p (empty) and sigma -> pi delocalisations

Solution

tert-Butyl cation has an empty p-orbital at C+, so the C-H sigma electrons delocalise as sigma -> p(empty). In 2-butene the C-H sigma electrons of the allylic methyls delocalise into the C=C pi system, i.e. sigma -> pi.

Related JEE Advanced Chemistry questions

• The transformation of C2H5CON to C2H5NCO demonstrates a rearrangement involving the migration of an alkyl group to which site?
• The hyperconjugative stabilities of tert-butyl cation and 2-butene, respectively, are due to -
• How many valid pairs (P1, P2) are possible such that 'P1-methylpent-P2-yne' is a correct IUPAC name, where P1 denotes the position of the methyl substituent and P2 denotes the position of the triple bond?
• In the Reimer-Tiemann reaction (phenol + CHCl3 + NaOH, heated), which intermediate is formed on the pathway to salicylaldehyde?
• How many of the following groups show a negative inductive (-I) effect? (a) -Cl (b) -CH3 (c) -O(-) (d) -COO(-) (e) -CMe3 (f) -F (g) -NH2 (h) -OH (i) -NO2 (j) -N=O (k) (+)-NH3
• How many of the following compounds are more acidic than ethanol (CH3-CH2-OH)? (a) CF3-CH2-OH (2,2,2-trifluoroethanol) (b) CH3-CF2-OH (1,1-difluoroethanol) (c) CH3-C(=O)-OH (acetic acid) (d) CH3-CH(OH)-CH3 (propan-2-ol)

⚔️ Practice JEE Advanced Chemistry free + battle 1v1 →