Electrophiles, nucleophiles, nucleophilicity and leaving groups

28 questions on Electrophiles, nucleophiles, nucleophilicity and leaving groups from the Organic Reaction Mechanisms I: Nucleophiles and Carbonyl Addition chapter: 6 NEET level, 11 JEE Main, 11 JEE Advanced. Each one opens with its answer and solution.

• Which of the following species is an electrophile? NEET level
• Which halide ion is the best leaving group when it is displaced from a primary alkyl halide R-X in an S_N2 reaction? NEET level
• Which of the following is the poorest leaving group? NEET level
• Which of the following is an ambident nucleophile (can attack through two different atoms)? NEET level
• Alcohols react with concentrated HBr much faster than with NaBr alone because NEET level
• Between CH3O- and CH3OH, which is the stronger nucleophile in the same solvent, and why? NEET level
• Four substrates CH3-X are treated with Br- under identical S_N2 conditions. The fastest reaction is shown by JEE Main level
• The pKa values of the conjugate acids are: CH3OH 15.5, C6H5OH 10.0, p-O2N-C6H4-OH 7.15, CH3COOH 4.76. For the four anions below, all attacking through oxygen wi... JEE Main level
• Ethyl bromide is warmed with ethanolic KCN. The main organic product is JEE Main level
• Following the NCERT convention, ethyl bromide is treated separately with (P) KNO2 and (Q) AgNO2. The main products are respectively JEE Main level
• Which carbonyl carbon is the most electrophilic? JEE Main level
• Count the ambident nucleophiles in the following list. Counting convention: a species is ambident if it has two different kinds of atoms (different elements) th... JEE Main level
• Using the rule that a good leaving group is the conjugate base of an acid with pKa below 0, select the good leaving group(s). Data: pKa of HCl -7; of CH3SO3H -1... JEE Main level
• Which of the following species can act as electrophiles? JEE Main level
• Which of the following is a good nucleophile but a very weak base? JEE Main level
• Compared with ethoxide, (CH3)3C-O- is JEE Main level
• Acid catalysis speeds up nucleophilic addition to a carbonyl compound mainly because JEE Main level
• The anions below are the conjugate bases of acids with the following acid dissociation constants K_a at 298 K: NO3-: 24, Cl-: 1x 10^7, CH3SO3-: 79, F-: 0.00068,... JEE Advanced level
• Ethyl 4-hydroxybutanoate, HO-CH2CH2CH2-CO-OC2H5, is converted completely into 4-methylpentane-1,4-diol using (i) CH3MgBr in dry ether; (ii) H3O+. The minimum nu... JEE Advanced level
• The acyl derivatives CH3COCl, (CH3CO)_2O, CH3COOC2H5 and CH3CONH2 release the leaving groups Cl-, CH3COO-, C2H5O- and NH2- in the second step of nucleophilic ac... JEE Advanced level
• Under mild conditions (room temperature, no forcing conditions or strong catalysts), which direct conversions by nucleophilic acyl substitution are feasible? JEE Advanced level
• An ambident nucleophile is defined here as an ion with two different kinds of nucleophilic atoms (different elements, or carbon and oxygen). Select the ambident... JEE Advanced level
• Select the correct statement(s). Take the pKa of water as 15.7 and of H3O+ as -1.7. JEE Advanced level
• The rate constants for nucleophilic addition to para-substituted benzaldehydes p-X-C6H4-CHO obey log_10(k/k_0) = rho sigma_p with rho = +1.8. Given sigma_p = +0... JEE Advanced level
• (R)-Butan-2-ol is treated with (i) p-CH3-C6H4-SO2Cl (TsCl), pyridine; (ii) NaBr, DMF. The final product is JEE Advanced level
• Unhindered amines attacking CH3I in the same solvent follow nucleophilicity that tracks basicity. The pKa values of the conjugate acids are: CH3NH3+ 10.6; NH4+ ... JEE Advanced level
• Cyanohydrin formation needs the cyanide ion as nucleophile. The pKa of HCN is 9.2 and the total cyanide concentration (HCN plus CN-) is fixed. When the pH of th... JEE Advanced level
• Considering both steric and electronic effects on the addition of a nucleophile such as HCN (cyanohydrin formation), the order of decreasing carbonyl reactivity... JEE Advanced level