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Reaction energy profiles, kinetic vs thermodynamic control

55 questions on Reaction energy profiles, kinetic vs thermodynamic control from the General Organic Chemistry III: Reaction Intermediates 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 III: Reaction Intermediates topics

In the energy profile of a single-step reaction, the species located at the top of the energy barrier is the NEET level
The difference in energy between the reactants and the transition state of a reaction step is called the NEET level
A reaction occurs in two steps through one reactive intermediate. Its energy profile between reactant and product shows NEET level
The rate-determining step of a multistep reaction is the step that NEET level
Buta-1,3-diene reacts with one equivalent of HBr at -80 degC (kinetic control). The major product is NEET level
Buta-1,3-diene reacts with one equivalent of HBr at 40 degC and the products are allowed to equilibrate (thermodynamic control). The major product is NEET level
Naphthalene is sulfonated with concentrated H2SO4 at 80 degC for a short time. The major product is NEET level
The kinetic product of a reaction in which two products can form from the same reactant is the product that NEET level
Which statement about intermediates and transition states is correct? NEET level
A catalyst increases the rate of a reaction by NEET level
In the energy profile of an exothermic reaction, the products are NEET level
Naphthalene-1-sulfonic acid is heated with concentrated H2SO4 at 160 degC for a long time (only monosulfonated species need be considered). The major product at... JEE Main level
At 160 degC naphthalene-2-sulfonic acid is the thermodynamically favoured product. The best reason is that JEE Main level
At low temperature, electrophilic substitution of naphthalene occurs faster at C-1 than at C-2. The best explanation is that JEE Main level
2-Methylcyclohexan-1-one is treated with one equivalent of LDA in THF at -78 degC. The major enolate is formed by removal of JEE Main level
For 2-methylcyclohexan-1-one, the thermodynamic (more substituted) enolate is favoured by JEE Main level
The relative energies (kJ/mol) of the stationary points of a reaction R -> I1 -> I2 -> P are: R = 0, TS1 = 55, I1 = 15, TS2 = 85, I2 = 30, TS3 = 50, P = -25. Th... JEE Main level
Buta-1,3-diene adds HBr faster at C-1,C-2 than at C-1,C-4 at -80 degC. The best explanation is that JEE Main level
Assertion (A): At 40 degC, the addition of HBr to buta-1,3-diene gives mainly 1-bromobut-2-ene. Reason (R): 1-Bromobut-2-ene has a disubstituted C=C, more stabl... JEE Main level
For the isomerisation K <=> T at 298 K, Delta G deg = -5.50 kJ mol^-1 (R = 8.314 J mol^-1 K^-1). The mole percent of T in the equilibrium mixture is closest to JEE Main level
Match the reaction in Column I with the type of control in Column II. Column I: (P) HBr + buta-1,3-diene at -80 degC; (Q) naphthalene + conc. H2SO4 at 160 degC ... JEE Main level
Reactant A gives products P1 and P2 in parallel, irreversible first-order reactions. E_a(P1) < E_a(P2) and both pre-exponential factors are equal. On raising th... JEE Main level
Consider (i) CH3Br + I^- -> CH3I + Br^- (single-step S_N2) and (ii) (CH3)3CBr + Cl^- -> (CH3)3CCl + Br^- by an S_N1 path in two steps (ionisation, then capture ... JEE Main level
According to the Hammond postulate, in a strongly exothermic step the transition state JEE Main level
On warming, 3-bromobut-1-ene and 1-bromobut-2-ene interconvert in a polar medium. The common species through which they interconvert is JEE Main level
LDA gives the kinetic enolate of an unsymmetrical ketone mainly because JEE Main level
A forward step has E_a = 45 kJ mol^-1 and Delta H = -30 kJ mol^-1. The activation energy of the reverse step is JEE Main level
A reaction has E_a = 60.0 kJ mol^-1 (R = 8.314 J mol^-1 K^-1). The ratio k(310 K)/k(300 K) is closest to JEE Main level
The relative energies (kJ/mol) of successive stationary points along a reaction path, from reactant to product, are: 0, 48, 20, 66, 35, 41, 12, 58, -15. Every i... JEE Main level
For a two-step reaction A -> B -> C in which B is a reactive intermediate, which statements are correct? JEE Main level
Buta-1,3-diene reacts with one equivalent of HBr. Which statements are correct? JEE Main level
Concerning the sulfonation of naphthalene with conc. H2SO4, which statements are correct? JEE Main level
For 2-methylcyclohexan-1-one, which statements are correct? JEE Main level
A reaction R -> I -> P has relative energies (kJ/mol): R = 0, TS1 = 72, I = 30, TS2 = 55, P = -40. Taking the effective activation energy of the overall reverse... JEE Advanced level
Conformers A and B interconvert much faster than either reacts, and each gives a different product irreversibly (A gives PA, B gives PB). B is 8.0 kJ mol^-1 hig... JEE Advanced level
Assertion (A): When two conformers interconvert much faster than they react, the product ratio generally differs from the equilibrium ratio of the conformers. R... JEE Advanced level
Assertion (A): The 1,2-adduct of HBr and buta-1,3-diene formed at -80 degC does not rearrange to the 1,4-adduct if kept at that temperature, even though the rea... JEE Advanced level
Assertion (A): Sulfonation of naphthalene at 80 degC gives mainly naphthalene-1-sulfonic acid. Reason (R): Naphthalene-1-sulfonic acid is thermodynamically more... JEE Advanced level
The 1,2-adduct and 1,4-adduct of HBr with buta-1,3-diene equilibrate at 313 K. For 1,2-adduct -> 1,4-adduct, Delta G deg = -4.00 kJ mol^-1 (R = 8.314 J mol^-1 K... JEE Advanced level
A reaction A <=> I -> P has rate constants k_1 = 2.0x10^-3 s^-1 (A to I), k_-1 = 30 s^-1 (I to A) and k_2 = 20 s^-1 (I to P). Applying the steady-state approxim... JEE Advanced level
Match Column I with the major product in Column II. Column I: (1) HBr + buta-1,3-diene at -80 degC; (2) the same, equilibrated at 40 degC; (3) naphthalene + con... JEE Advanced level
Reactant A gives P1 and P2 by parallel first-order steps with k_1 = 4.0x10^-2 s^-1 and k_2 = 1.0x10^-2 s^-1. Each product can also revert to A, and at equilibri... JEE Advanced level
A reaction A -> B -> C has step 1 with forward E_a = 40 kJ mol^-1 and reverse E_a = 10 kJ mol^-1, and step 2 with forward E_a = 25 kJ mol^-1 and reverse E_a = 7... JEE Advanced level
3-Methylbutan-2-one, (CH3)2CH-CO-CH3, is treated with one equivalent of LDA in THF at -78 degC, and then with CH3I (alkylation of the enolate at carbon). The ma... JEE Advanced level
For A <=> B, the uncatalysed reaction has E_a,fwd = 85 kJ mol^-1 and E_a,rev = 110 kJ mol^-1. A catalyst lowers the forward barrier to 65 kJ mol^-1. For the cat... JEE Advanced level
Two conformers A and B do not interconvert during the reaction time (their interconversion barrier is far above both reaction barriers). They are present in equ... JEE Advanced level
For the isomerisation K -> T of a kinetic product K to the thermodynamic-looking isomer T, Delta H deg = -10.0 kJ mol^-1 and Delta S deg = -30.0 J mol^-1 K^-1 (... JEE Advanced level
Two products K (kinetic) and T (thermodynamic) interconvert, K <=> T. For K to T, Delta H deg = -12.0 kJ mol^-1 and Delta S deg = -15.0 J mol^-1 K^-1. At 300 K ... JEE Advanced level
A reaction R -> I1 -> I2 -> P has relative energies (kJ/mol): R = 0, TS1 = 60, I1 = 25, TS2 = 90, I2 = 40, TS3 = 55, P = -20. Which statements are correct? JEE Advanced level
Two conformers A and B interconvert rapidly (barrier lower than any reaction barrier), and each reacts irreversibly to PA and PB respectively. Which statements ... JEE Advanced level
A mixture of products K and T forms from a reactant and is under thermodynamic control. Which statements are correct? JEE Advanced level
3-Methylbutan-2-one, (CH3)2CH-CO-CH3, can give two enolates. Which statements are correct? JEE Advanced level
Reactant A gives K (E_a = 50.0 kJ mol^-1) and T (E_a = 65.0 kJ mol^-1) by parallel irreversible steps with equal pre-exponential factors (R = 8.314 J mol^-1 K^-... JEE Advanced level
In the acid-catalysed S_N1 hydrolysis of (CH3)3C-Br in water, the steps are: (1) ionisation to (CH3)3C+; (2) capture by H2O to give (CH3)3C-OH2+; (3) loss of H+... JEE Advanced level
Which statements are correct? JEE Advanced level