Hammond postulate and reactivity-selectivity

27 questions on Hammond postulate and reactivity-selectivity from the General Organic Chemistry III: Reaction Intermediates chapter: 5 NEET level, 11 JEE Main, 11 JEE Advanced. Each one opens with its answer and solution.

• The Hammond postulate states that the transition state of a reaction step NEET level
• According to the Hammond postulate, the transition state of a highly exothermic step NEET level
• Bromination of alkanes is more selective than chlorination mainly because hydrogen abstraction by Br^. is NEET level
• Among F^., Cl^. and Br^., the radical that abstracts hydrogen from an alkane with the highest selectivity is NEET level
• Free radical monobromination of propane gives mainly NEET level
• The hydrogen abstraction step by Cl^. from an alkane is only weakly selective between primary, secondary and tertiary C-H bonds. According to the Hammond postul... JEE Main level
• In the S_N1 hydrolysis of (CH3)3C-Br the rate-determining step is ionisation. The transition state of this step is best described as JEE Main level
• Monochlorination of 2-methylpropane (isobutane) is carried out, taking the relative reactivity per hydrogen as 1 deg : 3 deg = 1 : 5. The percentage of the tert... JEE Main level
• Under comparable conditions the three halogens F2, Cl2 and Br2 all halogenate an alkane through radicals. Which one gives a product distribution closest to the ... JEE Main level
• The first step of the acid-catalysed hydration of propene is addition of H+ to the double bond to give a carbocation. The proton goes to the terminal carbon bec... JEE Main level
• A reaction A -> B -> C has an endothermic first step (Delta H = +20 kJ mol^-1) and a highly exothermic second step (Delta H = -60 kJ mol^-1). B is an intermedia... JEE Main level
• Bond dissociation energies in kcal mol^-1: primary C-H 101, H-Cl 103, H-Br 88. The enthalpy changes (Delta H) of the hydrogen abstraction step R-H + X^. -> R^. ... JEE Main level
• In electrophilic nitration of anisole (C6H5-OCH3) the substitution occurs mainly at the ortho and para positions. In terms of the Hammond postulate this is beca... JEE Main level
• Relative reactivities per hydrogen for 1 deg : 2 deg C-H are 1 : 3.8 for chlorination and 1 : 82 for bromination of propane. The percentages of 2-halopropane in... JEE Main level
• Which of the following consequences of the Hammond postulate are correct? JEE Main level
• Which statements about radical halogenation of alkanes are correct (use C-H (secondary) about 98 kcal/mol, H-Br 88, H-Cl 103)? JEE Main level
• Assertion (A): Free radical bromination of alkanes is much more selective than chlorination. Reason (R): The hydrogen abstraction by Br^. is endothermic, so its... JEE Advanced level
• Assertion (A): Radical monobromination of 2-methylpropane gives 2-bromo-2-methylpropane almost exclusively (more than 99%, taking 1 deg : 3 deg = 1 : 1600 per H... JEE Advanced level
• Match each step with the description of its transition state according to the Hammond postulate. Column I: (P) Cl^. + secondary C-H (C-H 98, H-Cl 103 kcal/mol);... JEE Advanced level
• Take relative reactivities per hydrogen for radical bromination as 1 deg : 2 deg : 3 deg = 1 : 82 : 1600. How many times faster (per molecule, same conditions) ... JEE Advanced level
• A substituent stabilises a carbocation by 10 kcal mol^-1 relative to the unsubstituted cation. The transition state of the (endothermic) ionisation step that fo... JEE Advanced level
• Which of the following changes would make the radical chlorination of an alkane LESS selective (product distribution closer to the statistical one)? JEE Advanced level
• Bond energies in kcal mol^-1: primary C-H 101, tertiary C-H 96, H-Cl 103, H-Br 88. Of the following hydrogen abstractions, the transition state expected to be t... JEE Advanced level
• For the ionisation R-X -> R+ + X- (rate-determining step of S_N1), which conclusions from the Hammond postulate are correct? JEE Advanced level
• Using the Hammond postulate with bond energies (kcal/mol: C-H in methane 105, H-F 136, H-Br 88), which steps are expected to have EARLY (reactant-like) transiti... JEE Advanced level
• Which statements concerning reactivity and selectivity in radical halogenation are correct? JEE Advanced level
• Butane is monohalogenated by a free radical path. Take relative reactivities per hydrogen 1 deg : 2 deg as 1 : 3.8 for chlorination and 1 : 82 for bromination. ... JEE Advanced level